Engine Controls - Tests W/codes - 4.6l Cadillac Eldorado X

INTRODUCTION

Most engine control problems are the result of mechanical breakdowns, poor electrical connections or damaged vacuum hoses. Before considering the computer system as a possible cause of problems, perform checks and inspections covered in the BASIC TESTING article. Failure to do so may result in lost diagnostic time.

If no faults found performing procedures in the BASIC TESTING article, proceed with DIAGNOSTIC PROCEDURE under SELF-DIAGNOSTIC SYSTEM. If no fault codes are present and driveability problems exist, proceed to the TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.). If only intermittent codes are present, see INTERMITTENTS in the TESTS W/O CODES article.

SELF-DIAGNOSTIC SYSTEM

Note. For On-Board Diagnostic System Check see the BASIC TESTING article.

Note. Powertrain Control Module (PCM) may also be referred to as Vehicle Control Module (VCM) in some diagnostic text and illustrations. Terms may be used interchangeably.

PCM/VCM is equipped with a self-diagnostic system, which detects system failures or abnormalities. When a malfunction occurs, PCM/VCM will store a Diagnostic Trouble Code (DTC) and, in most cases, illuminate the Malfunction Indicator Light (MIL) located on instrument cluster. Malfunctions are recorded as hard failures or as intermittent failures.

There are 4 types of DTC category

1. Type "A" - Emissions related, turns on MIL the first time DTC sets.
2. Type "B" - Emissions related, turns on MIL if fault is active for 2 consecutive driving cycles.
3. Type "C" - Non-emissions related, does not turn on MIL, but will turn on SERVICE light.
4. Type "D" - Non-emissions related, does not turn on MIL or SERVICE light.

HARD FAILURES

Most hard failures cause MIL to illuminate and remain on until malfunction is repaired. If MIL comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined. See DIAGNOSTIC PROCEDURE .

If a sensor fails, PCM/VCM will use a substitute value in its calculations to continue engine operation. In this condition, vehicle is functional, but it will most likely display degraded driveability.

INTERMITTENT FAILURES

Intermittent failures cause MIL to flicker or glow and go out about 10 seconds after intermittent fault goes away. Corresponding DTC, however, will be retained in PCM/VCM memory. If related fault does not reoccur within 50 engine starts, trouble code will be erased from control module memory. Intermittent failures may be caused by sensor, connector or wiring related problems. See INTERMITTENTS in the TESTS W/O CODES article.

Note. OBD II vehicles have options available in the scan tool DTC mode to display enhanced information available. However, to fully utilize information and procedures requires the use of a Tech 1 or 2 scan tool. See scan tool operator's manual for additional information.

The following are Tech 1 or 2 scan tool sub-menus in the DTC INFO and SPECIFIC DTC modes

DTC INFO MODE

Used to search for a specific type of stored DTC information. There are 7 choices in this mode. Technician may be instructed to test DTC(s) in a certain manner. Follow the affected DTC test procedures. To get complete description of any status, hit ENTER key before pressing the desired F-key.

DTC STATUS

This selection will display any DTC(s) that have not run during the current ignition cycle or have reported a test failure during this ignition up to a maximum of 33 DTCs. DTC test which run and passed will cause that affected DTC to be removed from scan tool screen.

FAIL THIS IGN.

This selection will display all DTCs that have failed during the present ignition cycle.

HISTORY

This selection will display only DTC(s) that are stored in the control module's history memory. It will not type "B" DTCs. It will display all type "A" and type "B" DTCs that have the MIL illuminated and have failed within the last 40 warm-up cycles. It will also display type "C" DTCs that have failed within the 40 warm-up cycles.

LAST TEST FAIL

This selection will display only DTCs that have failed the last time the test ran. The last test may have ran during the previous ignition cycle, if a type "A" or "B" DTC is displayed. For type "C" DTCs, the last failure must have occurred during the current ignition cycle to be displayed as LAST TEST FAIL.

MIL REQUEST

This selection will display only DTCs that are requesting the MIL. Type "C" DTCs cannot be displayed using this option. This selection will report type "B" DTCs only after the MIL has been requested.

NOT RUN SCC

Not Run Since Code Clear option will display up to 33 DTCs that have not run since DTCs were last cleared. Since any displayed DTCs have not run, their condition (passing or failing) is unknown.

TEST FAIL SCC

Test Fail Since Code Clear selection will display all active and history DTCs that have reported a test failure since the last time DTCs were cleared. DTCs that last failed over 40 warm-up cycles before this option is selected will not be displayed.

FAILED SINCE CLEAR

This message indicates the DTC has failed at least once within the last 40 warm-up cycles since the last time DTCs were cleared.

NOT RUN SINCE CL.

Not Run Since Cleared message indicates that the selected diagnostic test has not run since the last time DTCs were cleared. Therefore, the diagnostic test status (passed or failed) is unknown. After DTCs are cleared, this message will continue to be displayed until the diagnostic test runs.

NOT RUN THIS IGN.

Not Run This Ignition message indicates the selected diagnostic test has not run this ignition cycle.

TEST RAN AND PASSED

This message indicates the selected diagnostic test has

1. Passed the last test.
2. Ran and passed during this ignition cycle.
3. Ran and passed since DTCs were last cleared.
4. Test has not failed since DTCs were last cleared.

If this message is displayed, repair is done. If FAILED THIS IGN. message is displayed, repair is incomplete and further diagnosis is required.

DIAGNOSTIC PROCEDURE

Diagnosis of computerized engine control system should be performed in following order

1. Ensure all engine systems not related to computer system are operating properly. DO NOT proceed with testing unless all other problems have been repaired. ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK must be performed before using specific DTC testing procedure. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article.
2. If DTC(s) were displayed, determine whether codes are hard or intermittent trouble codes. Hard codes will cause MIL to illuminate continuously while engine is running. See «HARD OR INTERMITTENT TROUBLE CODE DETERMINATION»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__hard-or-intermittent-trouble-code-determination) . For diagnosing hard codes, proceed to appropriate DTC test. For diagnosing intermittent codes, proceed to INTERMITTENTS in the TESTS W/O CODES article.
3. If no DTCs are present and a driveability problem exists, refer to SYMPTOMS in the TESTS W/O CODES article. Doing so will help identify proper system or component to check in the SYSTEM/COMPONENT TESTS article.
4. After necessary repairs are made, clear DTCs, verify vehicle will enter "closed loop" operation and ensure DTC does not reset.

READING TROUBLE CODES

Note. Use of Tech 1 or 2 scan tool is required to retrieve DTCs. Refer to user reference manuals supplied with scan tool.

TROUBLE CODE DEFINITIONS

TROUBLE CODE DEFINITION

HARD OR INTERMITTENT TROUBLE CODE DETERMINATION

During any diagnostic procedure, determine if DTC(s) are hard failure codes or intermittent failure codes. Diagnostic procedures will not always help analyze intermittent codes. To determine hard codes and intermittent codes

1. Enter diagnostic mode. Read and record all stored DTCs. Exit diagnostic mode, and clear DTCs. See «CLEARING DIAGNOSTIC TROUBLE CODES (DTC)»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__clearing-diagnostic-trouble-codes-dtc) .
2. Apply parking brake, and place transmission in Neutral or Park. Block drive wheels, and start engine. MIL should go out. Operate warm engine at specified RPM for 2 minutes and note MIL.
3. If MIL illuminates, enter diagnostic mode. Read and record DTCs. This will reveal hard failure codes. Oxygen sensor related codes may require a road test to reset hard failure after DTCs were cleared.
4. If MIL does not illuminate, all stored DTCs were intermittent failures, except as noted above. NOTE: DTCs will be recorded at various operating times. Some codes require operation of that sensor or switch for 5 seconds; others require operation for 5 minutes or longer at normal operating temperature, vehicle speed and load. Therefore, some DTCs may not set in a service bay operational mode and may require road testing vehicle in order to duplicate conditions under which code will set.

CLEARING DIAGNOSTIC TROUBLE CODES (DTC)

To clear DTCs from memory, either to determine if malfunction will occur again or after making necessary repairs, disconnect power supply to ECM/PCM/VCM for at least 30 seconds or clear codes using a scan tool.

ECM/PCM/VCM LOCATION

On most models, ECM/PCM/VCM is located behind right or left side of dash, behind right or left kick panel, or on left or right side of engine compartment. For more precise location, see COMPONENT LOCATIONS in the SYSTEM/COMPONENT TESTS article.

Diagnostic Aids

Diagnostic aids are additional tips used to help diagnose trouble codes when inspected circuit is okay. Diagnostic aids may help lead to a definitive solution to trouble code problem.

SPECIAL TOOLS (DIAGNOSTIC)

Note. A scan tool plugged into DLC is used to read DTCs and check voltages in system on serial data line. A scan tool is REQUIRED to retrieve vehicle information.

Computerized engine control system is most easily diagnosed using scan tool; however, other tools may aid in diagnosing problems. These tools are a tachometer, test light, ohmmeter, digital voltmeter with a 10-megohm input impedance (minimum), vacuum pump, vacuum gauge, fuel injector test lights and 6 jumper wires 6" long (one wire with female connectors at both ends, one wire with male connectors at both ends and 4 wires with male and female connectors at opposite ends). A test light, rather than a voltmeter, must be used when indicated by a diagnostic test. In addition, special jumper harnesses or testers may be required by manufacturer to facilitate diagnosis.

SCAN TOOL USAGE

Note. Before connecting scan tool to vehicle, diagnostic system should be checked to determine if system is operating properly and if information received will be accurate. This is done by performing ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK located in the BASIC TESTING article. If vehicle does not pass OBD system check, information received may be invalid.

Scan tool is a specialized tester which, when plugged into DLC, can be used to diagnose on-board computer control systems by providing instant access to circuit voltage information without need to crawl under dash or hood to backprobe sensors and connectors.

Scan tool cuts down diagnostic time dramatically by furnishing input data (voltage signals) which can be compared to specification parameters. See SCAN DATA . They may also furnish information on output device (solenoids and motors) status. However, status parameters only indicate output signals have been sent to devices by PCM/VCM; they do not indicate whether devices have responded properly to signal. Verify proper response at output device using a voltmeter or test light.

A problem may exist even if DTCs are not present. About 80 percent of driveability problems occur without DTCs. Sensors that are out of calibration will not set a DTC but will cause driveability problems.

Using a scan tool is the easiest method of checking sensor specifications and other data parameters. Scan tool is also useful in finding intermittent wiring problems by wiggling wiring harnesses and connections (key on, engine off) while observing data parameters. See SCAN DATA.

Note. If erroneous voltage signals are suspected, verify tester information using a digital voltmeter and wiring schematic. If non-existent codes are displayed, DO NOT use scan tool for diagnosis. Contact tester manufacturer for additional information.

SCAN DATA

Note. For scan data values, refer to scan tool manufacturer owner's manual or compare values with a known good component or vehicle.

SUMMARY

If no hard fault codes are present, driveability symptoms exist or intermittent DTC(s) exist, proceed to the TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.

CONNECTOR IDENTIFICATION

Note. For additional connector and terminal identification, see CONNECTOR IDENTIFICATION -- DEVILLE, ELDORADO & SEVILLE article.

Scheme 1

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Scheme 6

DIAGNOSTIC TROUBLE CODES

Note. Before clearing DTCs, perform On-Board Diagnostic (OBD) System Check. See the BASIC TESTING article. Record FREEZE FRAME and FAILURE RECORDS for reference during testing. Data will be erased when DTCs are cleared. If PCM/VCM is replaced, NEW PCM/VCM must be programmed using special manufacturer's equipment.

DTC P0101 - MAF SENSOR SYSTEM PERFORMANCE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

Circuit Description

This test determines if MAF sensor is providing proper readings to the PCM. MAF sensor is a high frequency device that measures the rate of airflow through the throttle body. MAF sensor outputs a series of pulses that varies in frequency with airflow. PCM uses this signal for fuel control.

MAF sensor readings during acceleration will be much higher than those during deceleration or idle. PCM calculates what MAF sensor reading should be from the sensor under certain conditions using engine speed (RPM), throttle position, and altitude parameters. When these test conditions are met, PCM will compare its calculated MAF value to the actual value received from the sensor. The calculated MAF reading is calculated by comparing MAP, RPM and IAT values. If difference between calculated MAF and actual MAF is too great, DTC will set.

Diagnostic Procedures

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check for stored DTC(s). If DTC P0106, P0108, P0112, P0113, P0300, P0401, P0441, P1108, P1404, P1406, P1441, P1508, P1509 or P1645 is also present, diagnose affected DTC(s) first. If DTC(s) are not present or after diagnosing affected DTC(s), go to next step.
3. Check vacuum leaks at MAF sensor seal, throttle body spacer, intake manifold, PCV, EGR valve, plate or tubes and brake booster and hoses. Repair as necessary and retest. If air leak is not found, go to next step.
4. Check for stuck or incorrect PCV valve. Check for air (unmetered) leaks at oil dipstick tube or oil filler cap. Repair as necessary and retest. If vacuum leak is not found, go to next step.
5. Using FREEZE FRAME and FAILURE RECORDS data function on scan tool, duplicate conditions under which DTC P0101 was set. If DTC resets, go to next step. If DTC does not reset, see DIAGNOSTIC AIDS.
6. Go to «DTC P0106»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0106-map-system-performance) and perform diagnostic test, then return to this step. If repairs were necessary, verify repairs and retest. If repairs were not necessary, go to next step.
7. Replace MAF sensor and retest.

For intermittent setting of DTC P0101, use FREEZE FRAME data under which the DTC set, looking for faulty data from other sensors which may set this DTC. An improperly installed air cleaner or a distorted snorkel may cause DTC to set. Check for proper air cleaner or snorkel installation.

DTC P0102 - MAF SENSOR CIRCUIT LOW FREQUENCY

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test determines if MAF sensor circuit failed, by monitoring the MAF signal. MAF sensor is a high-frequency device that measures the rate of airflow through the throttle body. MAF sensor outputs a series of pulses that varies in frequency with airflow. PCM uses this signal for fuel control.

MAF sensor readings during acceleration will be much higher than those during deceleration or idle. PCM reads the MAF sensor input each 4X ignition reference pulse. If MAF sensor output drops to less than 1135 Hz, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Start engine. Using scan tool, check MAF sensor reading. If reading is not greater than 1.3 gm/sec, go to next step. If reading is greater than 1.3 gm/sec, fault is not present.
3. Turn ignition off. Disconnect MAF sensor harness connector. Turn ignition on. Using DVOM, check voltage between ground and MAF sensor input circuit at PCM harness connector terminal. If voltage is 4-6 volts, go to next step. If voltage is not as specified, go to step 6).
4. Check voltage between ground and MAF sensor power circuit at MAF sensor harness connector. If voltage is not 10 volts or greater, go to step 7). If voltage is 10 volts or greater, go to next step.
5. Check voltage between MAF sensor harness connector ground and power circuits. If voltage is within 0.5 volt of voltage measured in step 4), go to step 9). If not, go to step 8).
6. Store fluid life index as indicated on scan tool. Turn ignition off. Wait 30 seconds, then disconnect PCM harness connector C2. Using DVOM, check MAF sensor input circuit for open or short to ground. Repair as necessary and verify repair. If input circuit is okay, go to step 11).
7. Repair open or short to ground in MAF sensor power feed circuit.
8. Repair open or high resistance in MAF sensor ground circuit.
9. Check terminal contact at MAF sensor. Repair as necessary. If terminal contact is okay, go to next step.
10. Replace MAF sensor.
11. Check terminal contact of MAF sensor input circuit at PCM harness connector. Repair as necessary. If terminal contact is okay, go to next step.
12. Replace PCM. Program replacement PCM using required equipment.

DTC P0103 - MAF SENSOR CIRCUIT HIGH FREQUENCY

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test determines if MAF sensor circuit failed, by monitoring the MAF signal. MAF sensor is a high-frequency device that measures the rate of airflow through the throttle body. MAF sensor outputs a series of pulses that varies in frequency with airflow. PCM uses this signal for fuel control.

MAF sensor readings during acceleration will be much higher than those during deceleration or idle. If PCM sees a MAF sensor signal higher than allowed or possible based on engine operation, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, select FREEZE FRAME function under SPECIFIC DTC. Duplicate conditions under which DTC was set. If DTC resets, go to next step. If DTC does not reset, see DIAGNOSTIC AIDS.
3. Check terminal contact at MAF sensor connector. Repair as necessary. If terminal contact is okay, go to next step.
4. Replace MAF sensor.

Check for Electromagnetic Interference (EMI) on MAF sensor wires, caused by wiring being too close to spark plug wires or high-power transmitters (mobile radio) operating in the vicinity. A battery charger may also set this DTC.

DTC P0105 - MAP SENSOR CIRCUIT INSUFFICIENT ACTIVITY

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test determines when the MAP sensor is sticking. The PCM does this by checking for throttle position changes that are not immediately followed by MAP signal changes. When a throttle position change of 3.2 degrees within .5 second occurs, the PCM watches the MAP signal for one second following the throttle position change. If MAP signal does not change by at least 4 kPa in this period and MAP sensor reading is greater than 17.3 kPa than the expected MAP reading (based on engine speed and throttle position), DTC will set.

Conditions for setting DTC

1. DTCs P0106, P0107, P0108, P0122, P0123 and P1108 not set.
2. MAP at least 21.5 kPa.
3. Engine vacuum at least 11.8 kPa.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, select FREEZE FRAME function under DTC mode. Note MAP value reading. If MAP value is .08 volt or less, perform DTC P0107 tests. If MAP value is not .08 volt or less, go to next step.
3. If MAP reading is 5.06 volts or greater than the value specified in step 2), perform DTC P0108 tests. If not, go to next step.
4. Check terminal contact at MAP sensor connector and PCM. Repair as necessary and verify repair. If terminal contact is okay, go to next step.
5. Replace MAP sensor.

DTC P0106 - MAP SYSTEM PERFORMANCE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test monitors TP sensor, engine speed, MAP, EGR flow and A/C clutch status. Engine operation denotes that a large change in manifold pressure must be preceded by a change in engine load due to changes in throttle angle, engine speed, EGR flow or A/C clutch status. If these parameters remain constant and there is a rapid change in MAP value, DTC will set.

Conditions for setting DTC

1. DTCs P0122 and P0123 not set.
2. Engine speed at 500 RPM or greater.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. If «DTC P0300»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0300-p0308-engine-misfire-detected) is also present, diagnose this DTC first. If DTC P0300 is not present, go to next step.
3. Turn ignition on, with engine off. Using scan tool, select ENGINE 1 function and note MAP display value. If MAP value is greater than 75 kPa (95 kPa at sea level), go to next step. If not, go to step 7).
4. Disconnect vacuum hose at MAP sensor. Connect a hand-held vacuum pump to MAP sensor. Slowly apply 20 in. Hg to sensor and note MAP display. Each one in. Hg applied to MAP sensor should result in a 4 kPa drop in MAP sensor reading. Watch for erratic reading. If reading is erratic, go to step 7). If reading changes smoothly, go to next step.
5. If MAP sensor reading is 34 kPa or less with 20 in. Hg applied to sensor, go to next step. If MAP sensor reading is greater than 34 kPa with 20 in. Hg applied, go to step 7).
6. Disconnect vacuum source from MAP sensor. If MAP sensor reading returns to original value, see DIAGNOSTIC AIDS. If MAP sensor reading does not return to original value, go to next step.
7. Replace MAP sensor.

Check for poor or open ground circuit causing an intermittent signal problem.

DTC P0107 - MAP SENSOR CIRCUIT LOW VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

MAP sensor is a sensor that changes resistance based upon manifold vacuum. PCM provides a 5-volt reference voltage and ground. Monitored MAP sensor signal varies between 1 and 5 volts as manifold vacuum varies. As MAP decreases, voltage decreases (low engine load, high vacuum). As MAP increases, voltage increases (high engine load, low vacuum). PCM uses MAP sensor values as an indicator of engine load. A short to ground or open condition would cause the MAP sensor signal to go low, setting DTC.

Conditions for setting DTC

1. DTCs P0122 and P0123 not set.
2. Engine speed at 700 RPM or less.
3. TP sensor at 18 degrees or less.

Or

1. DTCs P0122 and P0123 not set.
2. Engine speed at 1800 RPM or less.
3. TP sensor at 13 degrees or greater.
4. Transaxle not in Park or Neutral.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, note MAP display. If MAP value displayed is 17 kPa or less, go to next step. If MAP value displayed is not 17 kPa or less, see DTC P0106 for diagnosis.
3. Turn ignition off. Disconnect MAP sensor harness connector. Jumper MAP sensor harness connector 5-volt reference terminal to signal circuit terminal. Turn ignition on. If scan data displays a value greater than 102 kPa, go to step 13). If scan data displays a value of 102 kPa or less, go to next step.
4. Remove jumper wire. Using DVOM, check voltage between MAP sensor harness connector 5-volt reference terminal and ground. If voltage reading is 4.5 volts or greater, go to next step. If voltage reading is not greater than 4.5 volts, go to step 7).
5. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector C1. Using DVOM, check resistance between ground and MAP sensor signal circuit in PCM harness connector C1. If resistance is 10,000 ohms or greater, go to next step. If resistance is not 10,000 ohms or greater, go to step 9).
6. Check resistance between MAP sensor signal circuit in PCM harness connector C1 and MAP sensor signal circuit at harness connector. If resistance is 5 ohms or greater, go to step 10). If resistance is not 5 ohms or greater, go to step 15).
7. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector C1. Using DVOM, check resistance between MAP sensor 5-volt reference circuit and ground. If resistance is 10,000 ohms or greater, go to next step. If resistance is not 10,000 ohms or greater, go to step 12).
8. Check resistance between MAP sensor 5-volt reference circuit at sensor harness connector and PCM harness connector C1 terminal. If resistance is 5 ohms or greater, go to step 11). If resistance is not 5 ohms or greater, go to step 15).
9. Repair short to ground in MAP sensor signal circuit.
10. Repair open in MAP sensor signal circuit.
11. Repair open in MAP sensor 5-volt reference circuit.
12. Repair short to ground in MAP sensor 5-volt reference circuit.
13. Check terminal contact at MAP sensor. Repair as necessary. If terminal contact is okay, go to next step.
14. Replace MAP sensor.
15. Check terminal contacts at PCM connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
16. Replace PCM. Program replacement PCM using required equipment.

DTC P0108 - MAP SENSOR CIRCUIT HIGH VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

MAP sensor is a sensor that changes resistance based upon manifold vacuum. PCM provides a 5-volt reference voltage and ground circuit. A PCM-monitored MAP sensor signal varies between ground and 5 volts as manifold vacuum varies. As MAP decreases, voltage decreases (low engine load, high vacuum). As MAP increases, voltage increases (high engine load, low vacuum). PCM uses MAP sensor values as an indicator of engine load.

If MAP sensor signal goes high, such as when the signal line is shorted to voltage or the MAP sensor is shorted internally, DTC will set.

Conditions for setting DTC

1. DTCs P0122 and P0123 not set.
2. Throttle angle 20.5 degrees or less.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, check and note MAP sensor display. If MAP value displayed is 102 kPa or greater, go to next step. If MAP value displayed is less than specification, see «DTC P0106»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0106-map-system-performance) for diagnosis.
3. Turn ignition off. Disconnect MAP sensor harness connector. Turn ignition on. If MAP sensor value is less than 16 kPa, go to next step. If MAP sensor value is not less than 16 kPa, go to step 5).
4. Using DVOM, check voltage between MAP sensor harness connector terminal "C" and ground. If voltage reading is greater than 5.5 volts, go to step 7). If voltage reading is not greater than 5.5 volts, go to step 8).
5. Check voltage between MAP sensor signal circuit and ground. If voltage reading is greater than .5 volt, go to next step. If voltage reading is not greater than .5 volt, go to step 10).
6. Repair short to voltage in MAP sensor signal circuit.
7. Repair short to battery voltage in MAP sensor 5-volt reference circuit.
8. Check terminal contact at MAP sensor. Repair as necessary. If terminal contact is okay, go to next step.
9. Replace MAP sensor.
10. Check MAP sensor signal circuit terminal contact at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
11. Replace PCM. Program replacement PCM using required equipment.

DTC P0111 - IAT SENSOR CIRCUIT PERFORMANCE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

The IAT sensor is a thermistor that varies resistance based on temperature. Low temperature will result in a high signal voltage. This test monitors IAT sensor voltage. If PCM detects a large change in sensor signal voltage in a .25 second period, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. If DTC P0112 or «DTC P0113»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0113-iat-sensor-circuit) is also present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
3. Turn ignition on. Using scan tool, select FAILURE RECORD in DTC mode and note IAT snapshot display. If snapshot reading is less than-29°F (-34°C), go to next step. If not, go to step 5).
4. An intermittent high resistance reading occurred on IAT sensor circuit. Check for open in IAT ground circuit and IAT signal circuit. Repair as necessary. If circuits are okay, go to step 7).
5. If snapshot IAT sensor reading is greater than 291°F (144°C), go to next step. If reading is not greater than 291°F (144°C), go to step 7).
6. An intermittent low resistance reading occurred on the IAT sensor circuit. Check for possible short to ground in IAT sensor signal circuit. Repair as necessary. If circuit is okay, go to next step.
7. Artificially raise IAT temperature, from cool to warm. As IAT sensor warms, watch IAT sensor reading on scan tool. Look for a skip or jump in the value. If a skip or jump is noted, go to next step. If value did not skip or jump, see DIAGNOSTIC AIDS.
8. Replace IAT sensor.

Artificially changing the IAT temperature can be done by careful warming using heat gun or by cooling IAT in refrigerator, then allowing it to warm.

IAT TEMPERATURE-TO-RESISTANCE VALUES

DTC P0112 - IAT SENSOR CIRCUIT LOW VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

The IAT sensor is a thermistor that varies resistance based on temperature. As temperature of sensor increases, resistance decreases. High temperature will result in a low signal voltage. DTC will set when PCM sees an IAT sensor reading of 282°F (139°C) when coolant temperature is less than 230°F (110°C).

Conditions for setting DTC

1. DTC P0117 and P0118 not set.
2. ECT at 230°F (110°C) or less.
3. Vehicle speed 15 MPH or greater.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select ENGINE 1 mode and note IAT display. If IAT temperature reading is 282°F (139°C) or greater, go to next step. If IAT temperature reading is not greater than 282°F (139°C), see DIAGNOSTIC AIDS.
3. Disconnect IAT sensor harness connector. If IAT temperature reading is 282°F (139°C) or greater, go to next step. If IAT temperature is not greater than 282°F (139°C), go to step 6).
4. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector. Using DVOM, check resistance between IAT signal circuit at harness connector and ground. If resistance is greater than 10,000 ohms, go to step 8). If resistance is not greater than 10,000 ohms, go to next step.
5. Repair short to ground in IAT sensor signal circuit.
6. Check terminal contact at IAT sensor. Repair as necessary. If terminal contact is okay, go to next step.
7. Replace IAT sensor.
8. Check terminal contact at PCM. Repair as necessary. If terminal contact is okay, go to next step.
9. Replace PCM. Program replacement PCM using required equipment.

IAT sensor can be damaged by backfire in intake manifold. If more than one IAT sensor has been replaced, check for signs of engine backfire.

DTC P0113 - IAT SENSOR CIRCUIT HIGH VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

The IAT sensor is a thermistor that varies resistance based on temperature. As temperature of sensor increases, resistance decreases. Low temperature will result in a high signal voltage. DTC will set when PCM sees an IAT sensor reading of -35°F(-37°C) or less with engine operating conditions that should have raised IAT temperature.

Conditions for setting DTC

1. DTCs P0101, P0102, P0117 and P0118 not set.
2. Engine speed 500 RPM or greater for 20 seconds.
3. Vehicle speed has been greater than 7 MPH for 5 seconds in this cycle.
4. MAF input 60 grams/sec. or less.
5. ECT 32°F (0°C) or greater.
6. ECT less than 32°F (0°C) and IAT at least 81°F (27°C) less than engine coolant temperature.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select ENGINE 1 mode and note IAT display. If IAT reading is -35°F (-37°C) or less, go to next step. If IAT reading is greater than -35°F (-37°C), see DIAGNOSTIC AIDS.
3. Disconnect IAT sensor harness connector. Using jumper wire, jumper IAT sensor harness connector terminals "A" and "B". If IAT reading is 247°F (147°C) or greater, go to next step. If IAT reading is less than 247°F (147°C), go to step 5).
4. Check terminal contact at IAT sensor. Repair as necessary. If terminal contact is okay, go to step 10).
5. Using jumper wire, jumper IAT sensor connector terminal "A" to ground. If IAT temperature reading is 247°F (147°C) or greater, go to next step. If IAT temperature reading is less than 247°F (147°C), go to step 7).
6. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Using DVOM, check resistance between IAT sensor ground circuit at harness connector and IAT sensor ground circuit to PCM connector C1. If resistance is not 5 ohms or less, go to step 8). If resistance is 5 ohms or less, go to next step.
7. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Using DVOM, check resistance between IAT harness connector terminal "A" and IAT sensor signal to PCM connector C2. If resistance is not 5 ohms or less, go to step 9). If resistance is 5 ohms or less, go to step 11).
8. Repair open in IAT sensor ground circuit.
9. Repair open in IAT sensor signal circuit.
10. Replace IAT sensor.
11. Check terminal contact at PCM harness connectors. Repair as necessary. If terminal contact is okay, go to next step.
12. Replace PCM. Program replacement PCM using required equipment.

IAT sensor can be damaged by backfire in intake manifold. If IAT sensor has been replaced more than once, check for signs of backfire.

Under severe cold weather conditions, this DTC could set if the actual outside temperature (IAT) is less than -35°F (-37°C) and ECT is at least 81°F (27°C) warmer than IAT.

DTC P0116 - ECT SENSOR CIRCUIT PERFORMANCE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

ECT sensor circuit uses 2 pull-up resistors for temperature sensing. When sensor resistance is high, indicating low temperature, the PCM uses a 3650 ohms resistor and a 348 ohms resistor in series. As temperature increases to 122°F (50°C), the sensor resistance will decrease to 973 ohms. This resistance corresponds to .97 volt at the PCM. At this point the PCM shifts to the single 348 ohms pull-up resistor to measure temperature at greater than 122°F (50°C).

The PCM monitors the voltage signal of the circuit and assumes that engine operation causes coolant temperatures to change at slow rates. This test monitors the ECT sensor voltage. If PCM detects a large change in sensor output voltage in a one second period, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. If DTC P0117 or «DTC P0118»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0118-ect-sensor-circuit) is present, diagnose affected DTC(s) first. If DTC(s) are not present, go to next step.
3. Turn ignition on. Using scan tool, select FAILURE REC under DTC mode and note ECT display. If the snapshot for ECT sensor reading is -35°F (-37°C) or less, go to next step. If snapshot ECT sensor reading is not less than -35°F (-37°C), go to step 5).
4. An intermittent high resistance reading occurred on the ECT sensor circuit. Check for open in ECT sensor ground and signal circuits. Repair as necessary. If circuits are okay, go to step 7).
5. If ECT snapshot reading is greater than 247°F (147°C), go to next step. If ECT snapshot reading is not greater than 247°F (147°C), go to step 7).
6. An intermittent low resistance reading occurred on the ECT sensor circuit. Check for short to ground in ECT sensor signal circuit. Repair as necessary. If circuits are okay, go to next step.
7. Allow engine to cool to less than 95°F (35°C). Start engine and raise ECT sensor temperature from cool to warm. As ECT sensor warms, watch ECT sensor reading on scan tool. Look for a skip or jump in the value. If a skip or jump is noted, go to next step. If value did not skip or jump, see DIAGNOSTIC AIDS.
8. Replace ECT sensor.

If fault is not present, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING article.

DTC P0117 - ECT SENSOR CIRCUIT LOW VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

ECT sensor is a thermistor whose resistance varies with temperature. As temperature of sensor increases, resistance decreases. A high coolant temperature will result in low signal voltage. DTC sets because coolant temperature cannot be greater than 247°F (147°C) when the IAT is less than 212°F (100°C) or the engine has been running long enough to cool the coolant to less than 247°F (147°C).

Conditions required to set DTC are

1. DTCs P0112 and P0113 not set.
2. IAT temperature at 212°F (100°C) or less.
3. DTCs P0122 and P0123 not set.
4. Engine running with throttle angle between 5-35 degrees for at least 3.5 minutes.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select ENGINE 1 and note ECT display. If temperature reading is 247°F (147°C) or greater, go to next step. If temperature reading is not 247°F (147°C) or greater, fault is not present.
3. Disconnect ECT sensor harness connector. If temperature reading is 18°F (-28°C) or less, go to step 6). If not, go to next step.
4. Store fluid life index as indicated on scan tool. Turn ignition on and wait 30 seconds, then disconnect PCM harness connector C2. Using DVOM, check resistance between ECT sensor signal circuit and ground. If resistance is greater than 5 ohms, go to step 8). If resistance is not greater than 5 ohms, go to next step.
5. Repair short to ground in ECT sensor signal circuit.
6. Check terminal contact at ECT sensor connector. Repair as necessary. If terminal contact is okay, go to next step.
7. Replace ECT sensor.
8. Check terminal contact of ECT sensor signal circuit at PCM connector C2. Repair as necessary. If terminal contact is okay, go to next step.
9. Replace PCM. Program replacement PCM using required equipment.

DTC P0118 - ECT SENSOR CIRCUIT HIGH VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

ECT sensor is a thermistor whose resistance varies with temperature. As sensor temperature increases, resistance decreases. A low coolant temperature will result in high signal voltage. DTC sets because coolant temperature cannot be less than -36°F (-38°C) when the IAT is greater than 23°F (-5°C) or when the engine has been running long enough to warm coolant to greater than -36°F (-38°C).

Conditions for setting DTC

1. DTCs P0112 and P0113 not set.
2. IAT sensor value is 23°F (-5°C) or greater.
3. DTCs P0122 and P0123 not set.
4. Engine running with throttle angle at 7 degrees or greater for at least 3.5 minutes.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select ENGINE 1 and note ECT display. If temperature reading is -36°F (-38°C) or less, go to next step. If temperature reading is not -36°F (-38°C) or less, fault is not present.
3. Disconnect ECT sensor harness connector. Using jumper wire, jumper ECT sensor connector terminals together. If temperature reading is greater than 275°F (135°C), go to step 9). If temperature reading is not greater than 275°F (135°C), go to next step.
4. Connect jumper from ECT sensor signal circuit to ground. If temperature reading is 275°F (135°C) or greater, go to step 6). If temperature reading is not greater than 275°F (135°C), go to next step.
5. Remove jumper wire. Store fluid life reading indicated in scan tool. Turn ignition off for 30 seconds then disconnect PCM harness connector. Using DVOM, check resistance of ECT sensor signal circuit between PCM connector and ECT sensor connector. If resistance is 5 ohms or less, go to step 11). If resistance is not 5 ohms or less, go to step 7).
6. Remove jumper wire. Store fluid life index indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector. Using DVOM, check resistance of sensor ground circuit between PCM harness connector and ECT sensor harness connector. If resistance is 5 ohms or less, go to step 11). If resistance is not 5 ohms or less, go to step 8).
7. Repair open in ECT sensor signal circuit.
8. Repair open in ECT sensor ground circuit.
9. Check terminal contact at ECT sensor. Repair as necessary. If terminal contact is okay, go to next step.
10. Replace ECT sensor.
11. Check ECT sensor ground and signal circuit terminal contact at PCM harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
12. Replace PCM. Program replacement PCM using required equipment.

If fault is not present, perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING article.

DTC P0120 - TP SENSOR SYSTEM PERFORMANCE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

TP sensor is a potentiometer. At low throttle angle, TP sensor voltage is low. PCM uses TP sensor signal voltage to determine idle, Wide Open Throttle (WOT), deceleration enleanment and acceleration enrichment. This test monitors both the MAP and TP sensors. Engine operation requires that any large change in throttle position must be followed by a change in manifold pressure. If MAP remains constant following a large change in throttle angle, DTC will set.

Conditions for setting DTC

1. DTCs P0107 and P0108 not set.
2. MAP greater than 21.8 kPa.
3. MAP not within 12 kPa or BARO pressure.
4. Engine speed less than 500 RPM.
5. Engine metal overtemp not active.
6. Traction control not active.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P0300 is also present. If «DTC P0300»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0300-p0308-engine-misfire-detected) is present, diagnose DTC P0300 first. If DTC P0300 is not present, go to next step.
3. If DTC P0121 or «DTC P0122»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0122-tp-sensor-circuit) is present, diagnose affected DTC first. If DTCs are not present, go to next step.
4. Using scan tool, select FAILURE REC. under DTC mode. Note TP sensor display. If snapshot TP sensor reading is zero degrees or less, go to next step. If snapshot TP sensor reading is not zero degrees or less, go to step 8).
5. An intermittent low voltage reading occurred on the TP sensor circuit. Check for possible open or short to ground in TP sensor signal circuit or open in 5-volt reference circuit. Repair as necessary. If circuits are okay, go to next step.
6. Slowly depress accelerator from closed throttle to wide open throttle. Note TP sensor reading. Watch for a sudden skip or jump in TP sensor reading. If reading skips or jumps, go to next step. If reading does not skip or jump, fault is not present.
7. Check for binding or sticky throttle. Check for chaffed TP sensor wires. Repair as necessary. If repairs were not necessary, go to step 11).
8. If snapshot TP sensor reading is greater than 85 degrees, go to next step. If the snapshot of TP sensor reading is not greater than 85 degrees, go to step 6).
9. An intermittent high voltage reading occurred on the TP sensor circuit. Check for open in TP sensor ground circuit or short in TP sensor signal circuit. Repair as necessary. If circuits are okay, go to next step.
10. Slowly depress accelerator from closed throttle to wide open throttle. Note TP sensor reading. Watch for a sudden skip or jump in TP sensor reading. If reading skips or jumps, go to next step. If reading does not skip or jump, fault is not present.
11. Replace TP sensor.

DTC P0121 - TP SENSOR CIRCUIT INSUFFICIENT ACTIVITY

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

TP sensor is a potentiometer. At low throttle angle, TP sensor voltage is low. PCM uses TP sensor signal voltage to determine idle, Wide Open Throttle (WOT), deceleration enleanment and acceleration enrichment. This test determines when the TP sensor reading is too high and out of its estimated range for the current engine speed. PCM monitors changes in TP sensor. If change is .6 degree or less within .1 second, PCM compares the current throttle position with a stored value. If current throttle position is greater than the stored value, TP sensor is considered stuck and DTC will set.

Conditions for setting DTC

1. DTCs P0106, P0107, P0108, P0122 and P0123 not set.
2. Engine speed 400 RPM or greater.
3. Throttle position changes less than 0.6 degrees in 0.1 second.
4. MAP pressure is less than or equal to 60.3 kPa.
5. Traction control not active.
6. All 8 cylinders not enabled.
7. Engine overheat not present.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, view TP sensor display. If TP sensor reading is greater than 0.1 volt, go to next step. If not, diagnose using «DTC P0122»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0122-tp-sensor-circuit) test.
3. Check TP sensor display while slowly depressing accelerator from closed to wide-open throttle. Check TP sensor display for a stuck condition. If a stuck condition is observed, go to next step. If not, diagnose using «DTC P0106»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0106-map-system-performance) test.
4. Replace TP sensor and verify repairs.

DTC P0122 - TP SENSOR CIRCUIT VOLTAGE LOW

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

TP sensor is a potentiometer. At low throttle angle, TP sensor voltage is low. PCM uses TP sensor signal voltage to determine idle, Wide Open Throttle (WOT), deceleration enleanment and acceleration enrichment. This test determines when the TP sensor reading is too high and out of its estimated range for the current engine speed. PCM monitors changes in TP sensor within a certain period of time. If change is .6 degrees or less within .1 second, PCM compares the current throttle position with a stored value. If current throttle position is greater than the stored value, TP sensor is considered stuck and DTC will set.

Conditions for setting DTC

1. Engine speed 600 RPM or greater.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select ENGINE 1 and note TP display. If TP sensor reads .1 volt or less, go to next step. If TP sensor does not read .1 volt or less, fault is not present. See DIAGNOSTIC AIDS.
3. Disconnect TP sensor harness connector. Jumper TP sensor 5-volt reference circuit and TP sensor signal circuit at sensor harness connector. If TP sensor reads 4.5 volts or greater, go to step 13). If TP sensor does not read 4.5 volts or greater, go to next step.
4. Using DVOM, check voltage between jumper wire and ground. If voltage is less than .5 volt, go to next step. If voltage is not less than .5 volt, go to step 8).
5. Remove jumper wire. Check voltage between TP sensor 5-volt reference circuit and ground. If voltage is 4.5 volts or greater, go to step 9). If voltage is not 4.5 volts or greater, go to next step.
6. Store fluid life index as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C1. Using DVOM, check resistance between ground and TP sensor 5-volt reference circuit at PCM connector. If resistance is 10,000 ohms or greater, go to next step. If resistance is not 10,000 ohms or greater, go to step 12).
7. Check resistance on TP sensor 5-volt reference circuit between PCM connector C1 and TP sensor harness connector. If resistance is 5 ohms or less, go to step 15). If 5-volt reference circuit resistance is not 5 ohms or less, go to step 10).
8. Store fluid life information as indicated on scan tool. Turn ignition off for 30 seconds and then disconnect PCM harness connector C1. Using DVOM, check resistance between TP sensor signal ground circuit at PCM connector C1 and TP sensor signal circuit at TP sensor harness connector. If resistance is 5 ohms or less, go to step 15). If resistance is not 5 ohms or less, go to step 11).
9. Repair short to ground in TP sensor signal circuit.
10. Repair open in TP sensor 5-volt reference circuit.
11. Repair open in TP sensor signal circuit.
12. Repair short to ground in TP sensor signal circuit, including splice to EGR valve.
13. Check terminal contact at TP sensor connector.
14. Replace TP sensor.
15. Check terminal contact at PCM connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
16. Replace PCM. Program replacement PCM using required equipment.

If no faults are found, check all PCM related ground connections.

Check for faulty connections or damaged harness. Ensure harness is not routed too close to high-voltage wires, such as spark plug cables. If connections and harness appear okay, observe scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location.

DTC P0125 - ECT EXCESSIVE TIME TO REACH CLOSED LOOP

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test monitors ECT sensor after timer reaches 4.25 minutes. The PCM looks at the test condition every second and increments the timer each time the test conditions are met. After 4.25 minutes, and if ECT drops to less than 41°F (5°C) for 3 seconds, DTC will set. If ECT is greater than 41°F (5°C) , the test will be considered passed regardless of timer. The timer will decrement if the PCM is disabling fuel to any cylinder during traction control maneuvers, acceleration reduction, torque management, etc. The timer will reset only when the engine stops running.

Conditions for setting DTC

1. DTCs P0112, P0113, P0117 or P0118 not set.
2. Engine running.
3. IAT at 32°F (0°C) or greater.
4. Vehicle speed at least 10 MPH.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select FAILURE REC. and note ECT display. If ECT sensor reads -35°F (-37°C) or less, diagnose using DTC P0117 test. If ECT sensor does not read less than -35°F (-37°C), go to next step.
3. Start and warm engine to normal operating temperature. Using scan tool, select DATA LIST, ENGINE 1 and note ECT display while engine is warming up. If ECT reading is erratic or skipping (rapid changing), go to step 6). If ECT reading is normal, go to next step.
4. After engine is fully warmed up (about 20 minutes), note ECT display. If ECT reading is less than 185°F (85°C), go to next step. If ECT reading is not less than 185°F (85°C), fault is not present. See DIAGNOSTIC AIDS.
5. Check ECT sensor ground and signal circuits for high resistance. Repair as necessary. If circuits are okay, repair cooling system.
6. Check terminal contact at ECT sensor. Repair as necessary. If terminal contact is okay, go to next step.
7. Replace ECT sensor.

If fault is not present, check for an intermittent cooling system problem.

DTC P0131 - HO2S CIRCUIT LOW VOLTAGE BANK 1, SENSOR 1 (REAR)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a .45 volt reference signal to the HO2S through the Bank 1 high signal circuit. When HO2S is cold, less than 392°F (200°C), the sensor signal voltage will be about .45 volt and PCM will keep the system in "open loop". When HO2S is warm, sensor will swing from rich to lean rapidly, at least one switch every 2 seconds, if PCM is in good control of air/fuel mixture.

If sensor stays at lean voltage for greater than 40 seconds during this test, DTC will set. DTC will also set when there is a sensor circuit fault giving a false lean indication or air/fuel ratio is actually lean due to a vacuum leak or fuel control system fault.

Conditions for setting DTC

1. DTCs P0101, P0102, P0103, P0107, P0108, P0117, P0118, P0121, P0122, P0123, P0132 and P0134 not set.
2. TP sensor between 5.4-25 degrees.
3. Coolant temperature is 179°F (81.5°C) or greater.
4. Closed loop fuel control enabled.
5. Oxygen sensor ready.
6. Engine speed 800 RPM or greater.
7. MAP sensor greater than 32 kPa.
8. Listed conditions met for 3 seconds.
9. DTC P0151 test runs and passes.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P0134 is also present. If DTC P0134 is present, diagnose this DTC first. If DTC P0134 is not present, go to next step.
3. If DTC was set because vehicle ran out of fuel, clear DTC. If vehicle did not run out of fuel, go to next step.
4. Start and warm engine until coolant temperature is at least 185°F (85°C) . Using scan tool, select ENGINE 1 and note bank 1, sensor 1 oxygen sensor voltage. If voltage remains at less than .3 volt for 30 seconds or greater, go to next step. If not, fault is not present. See DIAGNOSTIC AIDS.
5. Turn ignition off. Disconnect rear HO2S harness connector. Start engine. Using DVOM, check voltage between HO2S terminals "A" and "B". If voltage remains at less than .3 volt for 30 seconds or greater, diagnose using DTC P0133 test. If not, go to next step.
6. Store fluid life index as indicated in scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector C2. Using DVOM, check resistance to ground at rear HO2S harness connector terminal "B". If resistance is greater than 10,000 ohms, go to next step. If not, go to step 8).
7. Check resistance between rear HO2S harness connector terminals "A" and "B". If resistance is 5 ohms or less, go to step 9). If not, go to step 10).
8. Repair short to ground in rear H02S high signal circuit.
9. Repair rear HO2S high and low signal circuit shorted to each other.
10. Check terminal contact at PCM connector C2 HO2S high and low signal circuits. Repair as necessary. If terminal contacts are okay, go to next step.
11. Replace PCM. Program replacement PCM using required equipment. After repairs, go to next step.

Check snapshot data for front long and rear long term fuel trim values. If both banks were lean, check for a condition that would cause lean engine operation. If only the rear bank was lean, check for a condition that would cause only the rear bank to be lean, such as an intermittent short to ground in HO2S high signal circuit. Never solder HO2S wires.

DTC P0132 - HO2S CIRCUIT HIGH VOLTAGE BANK 1, SENSOR 1 (REAR)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a .45 volt reference signal to the HO2S through the Bank 1 high signal circuit. When HO2S is cold, less than 392°F (200°C), the sensor signal voltage will be about .45 volt and PCM will keep the system in "open loop". When HO2S is warm, sensor will swing from rich to lean rapidly, at least one switch every 2 seconds, if PCM is in good control of air/fuel mixture.

If sensor stays at rich voltage for greater than 40 seconds during this test, DTC will set. DTC will also set when there is a sensor circuit fault giving a false rich indication or air/fuel ratio is actually rich due to a fuel control system fault.

Conditions for setting DTC

1. DTCs P0101, P0102, P0103, P0107, P0108, P0117, P0118, P0121, P0122, P0123, P0132 and P0134 not set.
2. TP sensor between 5.4-25 degrees.
3. Coolant temperature at 179°F (81.5°C) or greater.
4. Closed loop control enabled.
5. Oxygen sensor ready.
6. Engine speed 800 RPM or greater.
7. MAP sensor greater than 32 kPa.
8. Listed conditions met for 3 seconds.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING article. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P0134 is also present, diagnose this DTC first. If DTC P0134 is not present, go to next step.
3. Start and warm engine until coolant temperature is at 185°F (85°C) or greater. Using scan tool, select ENGINE 1 and note oxygen sensor voltage. If voltage remains at .6 volt or greater for 30 seconds or greater, go to next step. If not, fault is not present. See DIAGNOSTIC AIDS.
4. Turn engine off. Disconnect rear HO2S sensor harness connector. Start engine. Using DVOM, check voltage between sensor terminals "A" and "B". If voltage remains at greater than .6 volt for 30 seconds or greater, diagnose using «DTC P0133»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0133-ho2s-slow-response) test. If not, go to next step.
5. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness terminal C2. Turn ignition on, with engine off. If voltage reading is greater than 0.1 volt, go to next step. If not, go to step 7).
6. Repair short to ground in HO2S high signal circuit.
7. Check terminal contact at PCM connector C2 to HO2S high and low signal circuits. Repair as necessary. If terminal contacts are okay, go to next step.
8. Replace PCM. Program replacement PCM using required equipment. After repairs, go to next step.

Check snapshot data for front and rear long term fuel trim values. If both banks were rich, check for a condition that would cause a rich engine operation. If only the rear bank was rich, check for a condition that would cause only the rear bank to be rich, such as an intermittent short to voltage in HO2S high signal circuit. Never solder HO2S wires.

DTC P0133 - HO2S SLOW RESPONSE BANK 1, SENSOR 1 (REAR)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a .45 volt reference signal to the HO2S through the Bank 1 high signal circuit. When HO2S is cold, less than 392°F (200°C), the sensor signal voltage will be about .45 volt and PCM will keep the system in "open loop". When HO2S is warm, sensor will swing from rich to lean rapidly, at least one switch every 2 seconds, if PCM is in good control of air/fuel mixture. If oxygen sensor is slow to respond to changes on exhaust oxygen content, DTC will set.

Conditions for setting DTC

1. DTCs P0117, P0118, P0121, P0122, P0123, P0135 and P1133 not set.
2. Test not completed this ignition cycle.
3. Low coolant level not present.
4. Ignition voltage 9-16 volts.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. If you are referred here from another DTC, go to step 4). If not, go to next step.
3. If any other DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
4. Start and warm engine until coolant temperature reaches about 185°F (85°C) or greater. Using scan tool, select ENGINE 1 and note bank 1 sensor 1 voltage display. Increase engine speed to 1200-2000 RPM for about 2 minutes. After 2 minutes rear HO2S reading should swing rapidly within .3-.6 volt range. If voltage reading is within range, go to step 6). If voltage reading is out of range, go to next step.
5. With engine speed still at 1200-2000 RPM, note LOOP STATUS on scan tool. If system is in "closed loop", go to step 10). If system is not in "closed loop", go to step 9).
6. If HO2S voltage stays between .3 and .6 volt longer than the time is swings out of range, go to step 9). If not, go to next step.
7. Check terminal contact for HO2S high and low signal voltage at PCM connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
8. Check terminal contact at rear oxygen sensor. Repair as necessary. If terminal contact is okay, go to next step.
9. Replace rear HO2S. Check for possible oxygen sensor contamination such as, leaded fuel, incorrect gasket sealer or over rich operation.
10. Check for possible causes of extended rich or lean operation. Repair as necessary.

DTC P0134 - HO2S INSUFFICIENT ACTIVITY BANK 1, SENSOR 1 (REAR)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a .45 volt reference signal to the HO2S through the Bank 1 high signal circuit. When HO2S reaches operating temperature, it will generate a counter voltage that will vary based on the amount of oxygen in the exhaust. A lean exhaust will generate a low voltage and cause the reference voltage (.45 volt) to drop lower. A rich exhaust will generate a high voltage and cause the reference voltage to increase. If sensor cannot respond under the test conditions and generate a voltage greater than .61 volt or less than .31 volt, DTC will set.

Conditions for setting DTC

1. DTCs P0117, P0118, P0121, P0122, P0123 and P0560 not set.
2. Coolant temperature at 163°F (72.5°C) or greater.
3. Throttle angle between 1-81.6 degrees.
4. Calculated throttle position switch open.
5. Engine speed 800 RPM or greater.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Start and warm engine until coolant temperature reaches about 185°F (85°C) or greater. Using scan tool, select ENGINE 1 and note bank 1 sensor 1 voltage display for 30 seconds. If voltage remains between .3 and .6 volt, go to next step. If voltage does not remain between .3 and .6 volt, go to step 6).
3. Turn ignition off. Disconnect rear HO2S harness connector. Start engine. Using DVOM, check voltage between HO2S harness connector terminals "A" and "B". If voltage remains between .3 and .6 volt, diagnose using «DTC P0133»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0133-ho2s-slow-response) test. If voltage does not remain between .3 and .6 volt, go to next step.
4. Store fluid life index as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Using DVOM, check resistance between HO2S high signal circuit at PCM connector and HO2S harness connector terminal "B". If resistance is 5 ohms or less, go to next step. If not, go to step 9).
5. Check resistance between PCM connector C2 HO2S low signal circuit and HO2S harness connector terminal "A". If resistance is 5 ohms or less, go to next step. If not, go to step 10).
6. Turn ignition on, with engine off. Check voltage between HO2S harness connector terminals "C" and "D". If voltage is greater than 10.5 volts, go to next step. If not, go to step 8).
7. Using a jumper wire, jumper HO2S harness connector terminals "C" and "D". Set DVOM to amp scale. Connect DVOM in series between HO2S terminals "D" to "D" (harness to sensor). If reading is 0.9-1.5 amps, go to step 14). If not, go to step 13).
8. Check voltage between oxygen sensor harness connector terminal "D" to ground. If reading is 10.5 volts or greater, go to step 11). If not, go to next step.
9. Repair open in HO2S high signal circuit.
10. Repair open in HO2S low signal circuit.
11. Repair open in HO2S ground circuit.
12. Repair open or short to ground in HO2S ignition circuit.
13. Replace HO2S.
14. Check terminal contacts at PCM connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
15. Replace PCM. Program replacement PCM using required equipment. After repairs, go to next step.

DTC P0135 - HO2S HEATER CIRCUIT BANK 1, SENSOR 1 (REAR)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test determines if the heating element in the rear oxygen sensor is working properly. Oxygen sensor voltage is produced when the sensor reaches operating temperature and when the oxygen content of the exhaust stream is different than that in the atmosphere. The heating element is energized through the ignition signal circuit, when ignition is turned on, allowing sensor to reach operating temperature quickly. This in turn allows the PCM to enter into "closed loop" quicker. The voltage that the PCM measures on the oxygen sensor high and low inputs is called bias voltage. When bias voltage takes too long to vary (greater or less than bias voltage) after ignition is turned on, DTC will set.

Conditions for setting DTC

1. DTCs P0101, P0102, P0103, P0117, P0118 and P0134 not set.
2. ECT dropped at least 50°F (10°C) from end of the last ignition cycle to the beginning of this ignition cycle.
3. Ignition voltage 11 volts or greater.
4. Average rear HO2S bias voltage 352-546 mV.
5. Engine did not stall during test.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Disconnect rear oxygen sensor. Using DVOM, check voltage between sensor harness connector terminals "C" and "D". If voltage reading is greater than 10.5 volts, go to next step. If voltage reading is not greater than 10.5 volts, go to step 4).
3. Using jumper wire, jumper sensor connector terminal "C" to harness connector terminal "C". Set DVOM to amp scale. Connect DVOM in series with sensor terminal "D" to sensor harness connector terminal "D". If DVOM reads 0.9-1.5 amps, go to step 5). If not, go to next step.
4. Check voltage from harness connector terminal "D" to ground. If reading is 10.5 volts or greater, go to step 6). If reading is not 10.5 volts or greater, go to step 7).
5. Using scan tool, select FREEZE FRAME data and operate vehicle under the same conditions which set the DTC. If DTC resets, diagnose using DTC P0133 test. If DTC does not reset, fault is not present. See DIAGNOSTIC AIDS.
6. Repair open in HO2S ground circuit.
7. Repair open or short to ground in HO2S ignition signal circuit.
8. Replace HO2S.

An intermittent open in HO2S ignition signal circuit or ground circuit may cause DTC to set. A malfunctioning rear HO2S may also set DTC. Never solder oxygen sensor wires.

DTC P0137 - HO2S CIRCUIT LOW VOLTAGE BANK 1, SENSOR 2 (PRE-CONVERTER)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a .45 volt reference signal to the HO2S through the Bank 1 high signal circuit. When HO2S is cold, less than 392°F (200°C) , the sensor signal voltage will be about .45 volt and PCM will keep the system in "open loop". When HO2S is warm, sensor will swing from rich to lean rapidly, at least one switch every 2 seconds, if PCM is in good control of air/fuel mixture.

If sensor stays at lean voltage for greater than 40 seconds during this test, DTC will set. DTC will also set when there is a sensor circuit fault giving a false lean indication or air/fuel ratio is actually lean due to a vacuum leak or fuel control system fault.

Conditions for setting DTC

1. DTCs P0101, P0102, P0103, P0107, P0108, P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0133, P0134, P0151, P0152, P0153, P0154, P0300, P1133, P1153 and P1154 not set.
2. TP sensor between 5.4-25 degrees.
3. Coolant temperature at 179°F (81.5°C) or greater.
4. Closed loop fuel control enabled.
5. Oxygen sensors ready.
6. Engine speed at 800 RPM or greater.
7. MAP sensor greater than 32 kPa.
8. Listed conditions met for 3 seconds.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if «DTC P0140»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0140-ho2s-insufficient-activity) is also present. Diagnose this DTC first. If DTC P0140 is not present, go to next step.
3. Start and warm engine until coolant temperature is at least 185°F (85°C). Using scan tool, select ENGINE 1 and note bank 1, sensor 2 oxygen sensor voltage. If voltage remains at less than .3 volt for 30 seconds or greater, go to next step. If voltage does not remain at .3 volt or less for 30 seconds or greater, fault is not present. See DIAGNOSTIC AIDS.
4. Turn ignition off. Disconnect HO2S harness connector. Start engine. Using DVOM, check voltage between HO2S terminals "A" and "B". If voltage remains at less than .3 volt for 30 seconds or greater, diagnose using «DTC P0139»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0139-ho2s-slow-response) test. If voltage does not remain at .3 volt or less for 30 seconds or greater, go to next step.
5. Store fluid life index as indicated in scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector C2. Using DVOM, check resistance to ground at HO2S harness connector terminal "B". If resistance is greater than 10,000 ohms, go to next step. If resistance is not greater than 10,000 ohms, go to step 7).
6. Check resistance between HO2S harness connector terminals "A" and "B". If resistance is 5 ohms or less, go to step 8). If resistance is not 5 ohms or less, go to step 9).
7. Repair short to ground in H02S high signal circuit.
8. Repair HO2S high and low signal circuit shorted to each other.
9. Check terminal contact at PCM connector C2 HO2S high and low signal circuits. Repair as necessary. If terminal contacts are okay, go to next step.
10. Replace PCM. Program replacement PCM using required equipment.

Check snapshot data for front long and rear long term fuel trim values. If both banks were lean, check for a condition that would cause lean engine operation. If only the rear bank was lean, check for a condition that would cause only the rear bank to be lean, such as an intermittent short to ground in HO2S high signal circuit. Never solder oxygen sensor wires.

DTC P0138 - HO2S CIRCUIT HIGH VOLTAGE BANK 1, SENSOR 2 (PRE-CONVERTER)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a .45 volt reference signal to the HO2S through the bank 1 high signal circuit. When HO2S is cold, less than 392°F (200°C), the sensor signal voltage will be about .45 volt and PCM will keep the system in "open loop". When HO2S is warm, sensor will swing from rich to lean rapidly, at least one switch every 2 seconds, if PCM is in good control of air/fuel mixture.

If sensor stays at rich voltage for greater than 40 seconds during this test, DTC will set. DTC will also set when there is a sensor circuit fault giving a false rich indication or air/fuel ratio is actually rich due to a fuel control system fault.

Conditions for setting DTC

1. DTCs P0101, P0102, P0103, P0107, P0108, P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0133, P0134, P0151, P0152, P0153, P0154, P0300, P1133, P1153 and P1154 not set.
2. TP sensor 5.4-25 degrees.
3. Coolant temperature at 179°F (81.5°C) or greater.
4. Closed loop fuel control enabled.
5. Oxygen sensors ready.
6. Engine speed at 800 RPM or greater.
7. MAP sensor greater than 32 kPa.
8. Listed conditions met for 3 seconds.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if «DTC P0140»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0140-ho2s-insufficient-activity) is also present. Diagnose this DTC first. If DTC P0140 is not present, go to next step.
3. Start and warm engine until coolant temperature is at 185°F (85°C) or greater. Using scan tool, select ENGINE 1 and note oxygen sensor voltage. If voltage remains at .6 volt or greater for 30 seconds or longer, go to next step. If not, fault is not present. See DIAGNOSTIC AIDS.
4. Turn engine off. Disconnect HO2S sensor harness connector. Start engine. Using DVOM, check voltage between sensor terminals "A" and "B". If voltage remains at greater than .6 volt for 30 seconds or longer, diagnose using «DTC P0139»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0139-ho2s-slow-response) test. If not, go to next step.
5. Store fluid life index as indicated in scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM terminal C2. Turn ignition on. If voltage reading is greater than .1 volt, go to next step. If voltage reading is not greater than .1 volt, go to step 7).
6. Repair short to ground in HO2S high signal voltage.
7. Check terminal contact at PCM connector C2 to HO2S high and low signal circuits. Repair as necessary. If terminal contacts are okay, go to next step.
8. Replace PCM. Program replacement PCM using required equipment. After repairs, go to next step.

Check snapshot data for front long and rear long term fuel trim values. If both banks were rich, check for a condition that would cause a rich engine operation. If only the rear bank was rich, check for a condition that would cause only the rear bank to be rich, such as an intermittent short to voltage in HO2S high signal circuit. Never solder HO2S wires.

DTC P0139 - HO2S SLOW RESPONSE BANK 1, SENSOR 2 (PRE-CONVERTER)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a .45 volt reference signal to the HO2S through the Bank 1 high signal circuit. When HO2S is cold, less than 392°F (200°C), the sensor signal voltage will be about .45 volt and PCM will keep the system in "open loop". When HO2S is warm, sensor voltage will swing from rich to lean rapidly, at least one switch every 2 seconds, if PCM is in good control of air/fuel mixture. If oxygen sensor is slow to respond to changes on exhaust oxygen content, DTC will set.

Conditions for setting DTC

1. DTCs P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0141, P0151, P0152, P0153, P0154, P0155, P0171, P0172, P0174, P0175, P0300, P1133, P1134, P1139, P1153 and P1154 not set.
2. TP sensor between 5.4-25 degrees.
3. This test has not been completed this ignition cycle.
4. Low coolant level not present.
5. Ignition voltage between 9-16 volts.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. If you are referred here from another DTC, go to step 4). If not, go to next step.
3. If any other DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
4. Start and warm engine until coolant temperature is about 185°F (85°C) or greater. Using scan tool, select ENGINE 1 and note bank 1 sensor 2 voltage display. Increase engine speed to 1200-2000 RPM for about 2 minutes. After 2 minutes HO2S reading should swing rapidly outside the range of .3-.6 volt. If voltage rapidly swings outside of the range, go to step 9). If not, go to next step.
5. If HO2S voltage remains within .3-.6 volt longer than the time is swings out of range, go to step 8). If not, go to next step.
6. Check terminal contact for HO2S high and low signal voltage at PCM connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
7. Check terminal contact at oxygen sensor. Repair as necessary. If terminal contact is okay, go to next step.
8. Replace pre-converter HO2S. Check for possible oxygen sensor contamination such as, leaded fuel, incorrect gasket sealer or over rich operation.
9. Check for possible causes of extended rich or lean operation. Repair as necessary.

Never solder oxygen sensor wires.

DTC P0140 - HO2S INSUFFICIENT ACTIVITY BANK 1, SENSOR 2 (PRE-CONVERTER)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a .45 volt reference signal to the HO2S through the bank 1 high signal circuit. When HO2S reaches operating temperature, it will generate a counter voltage that will vary based on the amount of oxygen in the exhaust. A lean exhaust will generate a low voltage and cause the reference voltage (.45 volt) to drop lower. A rich exhaust will generate a high voltage and cause the reference voltage to increase. If sensor cannot respond under the test conditions and generate a voltage greater than .61 volt or less than .31 volt, DTC will set.

Conditions for setting DTC

1. DTCs P0117, P0118, P0121, P0122, P0123 and P0560 not set.
2. TP sensor between 1-81.6 degrees.
3. Coolant temperature at 163°F (72.5°C) or greater.
4. Throttle position switch open.
5. Engine speed at 800 RPM or greater.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Start and warm engine until coolant temperature reaches about 185°F (85°C) or greater. Using scan tool, select ENGINE 1 and note bank 1 sensor 2 voltage display for 30 seconds. If voltage remains .3-.6 volt, go to next step. If voltage does not remain .3-.6 volt, go to step 6).
3. Turn ignition off. Disconnect HO2S harness connector. Start engine. Using DVOM, check voltage between HO2S harness connector terminals "A" and "B". If voltage remains .3-.6 volt, diagnose using DTC P0139 test. If voltage does not remain .3-.6 volt, go to next step.
4. Store fluid life index as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM connector C2. Using DVOM, check resistance between HO2S high signal circuit at PCM connector and HO2S harness connector terminal "B". If resistance is 5 ohms or less, go to next step. If not, go to step 9).
5. Check resistance between PCM connector C2 HO2S low signal circuit and HO2S harness connector terminal "A". If resistance is 5 ohms or less, go to next step. If not, go to step 10).
6. Turn ignition on, with engine off. Check voltage between HO2S harness connector terminals "C" and "D". If voltage is greater than 10.5 volts, go to next step. If not, go to step 8).
7. Using a jumper wire, jumper HO2S harness connector terminals "C" and "D". Set DVOM to amp scale. Connect DVOM in series between HO2S terminals "D" to "D" (harness to sensor). If reading is 0.9-1.5 amps, go to step 14). If reading is not as specified, go to step 13).
8. Check voltage between oxygen sensor harness connector terminal "D" to ground. If reading is 10.5 volts or greater, go to step 11). If not, go to next step.
9. Repair open in HO2S high signal circuit.
10. Repair open in HO2S low signal circuit.
11. Repair open in HO2S ground circuit.
12. Repair open or short to ground in HO2S ignition circuit.
13. Replace HO2S.
14. Check terminal contacts at PCM connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
15. Replace PCM. Program replacement PCM using required equipment. After repairs, go to next step.

Never solder oxygen sensor wires.

DTC P0141 - HO2S HEATER CIRCUITY BANK 1, SENSOR 2 (PRE-CONVERTER)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test determines if the heating element in the pre-converter oxygen sensor is working properly. Oxygen sensor voltage is produced when the sensor reaches operating temperature and when the oxygen content of the exhaust stream is different than that in the atmosphere. The heating element is energized through the ignition signal circuit, when ignition is turned on, allowing sensor to reach operating temperature quickly. This in turn allows the PCM to enter into "closed loop" quicker. The voltage that the PCM measures on the oxygen sensor high and low inputs is called bias voltage. When bias voltage takes too long to vary (greater or less than bias voltage) after ignition is turned on, DTC will set.

Conditions for setting DTC

1. DTCs P0101, P0102, P0103, P0117, P0118 and P0140 not set.
2. ECT dropped at least 50°F (10°C) from end of last ignition cycle to the beginning of this ignition cycle.
3. Ignition voltage at 11 volts or greater.
4. Average pre-converter HO2S bias voltage is 352-546 mV.
5. Engine did not stall during test.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Disconnect pre-converter oxygen sensor. Using DVOM, check voltage between sensor harness connector terminals "C" and "D". If reading is greater than 10.5 volts, go to next step. If reading is less than 10.5 volts, go to step 4).
3. Using jumper wire, jumper sensor connector terminal "C" to harness connector terminal "C". Set DVOM to amp scale. Connect DVOM in series with sensor connector terminal "D" to harness connector terminal "D". If DVOM reads 0.9-1.5 amps, go to step 5). If DVOM reads less than 0.9 amp or greater than 1.5 amps, go to next step.
4. Check voltage from harness connector terminal "D" to ground. If reading is 10.5 volts or greater, go to step 6). If reading is less than 10.5 volts, go to step 7).
5. Using scan tool, select FREEZE FRAME data and operate vehicle under the same conditions which set the DTC. If DTC resets, diagnose using DTC P0139 test. If DTC does not reset, fault is not present. See DIAGNOSTIC AIDS.
6. Repair open in HO2S ground circuit.
7. Repair open or short to ground in HO2S ignition signal circuit.
8. Replace HO2S.

An intermittent open in HO2S ignition signal circuit or ground circuit may cause DTC to set. A malfunctioning pre-converter HO2S may also set DTC. Never solder oxygen sensor wires.

DTC P0143 - HO2S CIRCUIT LOW VOLTAGE BANK 1, SENSOR 3 (POST-CONVERTER)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a .45 volt reference signal to the HO2S through the Bank 1 high signal circuit. When HO2S is cold, less than 392°F (200C), the sensor signal voltage will be bias voltage of .45 volt and PCM will keep the system in "open loop". When HO2S is warm, sensor voltage will swing from rich to lean rapidly, at least one switch every 2 seconds, if PCM is in good control of air/fuel mixture.

If sensor stays at lean voltage for greater than 40 seconds during this test, DTC will set. DTC will also set when there is a sensor circuit fault giving a false lean indication or air/fuel ratio is actually lean due to a vacuum leak or fuel control system fault.

Conditions for setting DTC

1. DTCs P0101, P0102, P0103, P0107, P0108, P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0133, P0134, P0151, P0152, P0153, P0154, P0300, P1133, P1134, P1153 and P1154 not set.
2. TP sensor between 5.4-25 degrees.
3. Coolant temperature at 179°F (81.5°C) or greater.
4. Closed loop fuel control enabled.
5. Oxygen sensors ready.
6. Engine speed at 800 RPM or greater.
7. MAP sensor greater than 32 kPa.
8. Listed conditions met for 3 seconds.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if «DTC P0146»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0146-ho2s-circuit-insufficient) is also present. Diagnose DTC P0146 first, if present. If DTC P0146 is not present, go to next step.
3. Start and warm engine until coolant temperature is at least 185°F (85C). Using scan tool, select ENGINE 1 and note bank 1, sensor 3 oxygen sensor voltage. If voltage remains at less than .5 volt for 30 seconds or greater, go to next step. If voltage does not remain at .5 volt or less for 30 seconds or greater, fault is not present. See DIAGNOSTIC AIDS.
4. Turn ignition off. Disconnect HO2S harness connector. Start engine. Using DVOM, check voltage between HO2S terminals "A" and "B". If voltage remains at less than .5 volt for 30 seconds or greater, diagnose using «DTC P0139»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0139-ho2s-slow-response) test. If voltage does not remain at .5 volt or less for 30 seconds or greater, go to next step.
5. Store fluid life index as indicated in scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Using DVOM, check resistance to ground at HO2S harness connector terminal "B". If resistance is greater than 10,000 ohms, go to next step. If not, go to step 7).
6. Check resistance between HO2S harness connector terminals "A" and "B". If resistance is 5 ohms or less, go to step 8). If not, go to step 9).
7. Repair short to ground in HO2S high signal circuit.
8. Repair HO2S high and low signal circuit shorted to each other.
9. Check terminal contact at PCM connector C2 HO2S high and low signal circuits. Repair as necessary. If terminal contacts are okay, go to next step.
10. Replace PCM. Program replacement PCM using required equipment.

Check snapshot data for front long and rear long term fuel trim values. If both banks were lean, check for a condition that would cause lean engine operation. If only the rear bank was lean, check for a condition that would cause only the rear bank to be lean, such as an intermittent short to ground in HO2S high signal circuit. Never solder oxygen sensor wires.

DTC P0144 - HO2S CIRCUIT VOLTAGE HIGH BANK 1, SENSOR 3 (POST-CONVERTER)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a .45 volt reference signal to the HO2S through the Bank 1 high signal circuit. When HO2S is cold, less than 392°F (200°C), the sensor signal voltage will be about .45 volt and PCM will keep the system in "open loop". When HO2S is warm, sensor will swing from rich to lean rapidly, at least one switch every 2 seconds, if PCM is in good control of air/fuel mixture.

If sensor stays at rich voltage for greater than 40 seconds during this test, DTC will set. DTC will also set when there is a sensor circuit fault giving a false rich indication or air/fuel ratio is actually rich due to a fuel control system fault.

Conditions for setting DTC

1. DTCs P0101, P0102, P0103, P0107, P0108, P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0133, P0134, P0151, P0152, P0153, P0154, P0300, P1133, P1134, P1153 and P1154 not set.
2. TP sensor between 5.4-25 degrees.
3. Coolant temperature at 179°F (81.5°C) or greater.
4. Closed loop fuel control enabled.
5. Oxygen sensors ready.
6. Engine speed at 800 RPM or greater.
7. MAP sensor greater than 32 kPa.
8. Listed conditions met for 3 seconds.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if «DTC P0146»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0146-ho2s-circuit-insufficient) is also present. Diagnose DTC P0146 first, if present. If DTC P0146 is not present, go to next step.
3. Start and warm engine until coolant temperature is at 185°F (85°C) or greater. Using scan tool, select ENGINE 1 and note oxygen sensor voltage. If voltage remains at .9 volt or greater for 30 seconds or greater, go to next step. If not, fault is not present. See DIAGNOSTIC AIDS.
4. Turn engine off. Disconnect HO2S sensor harness connector. Start engine. Using DVOM, check voltage between sensor terminals "A" and "B". If voltage remains at greater than .9 volt for 30 seconds or greater, go to step 7). If voltage does not remain at greater than .9 volt after 30 seconds, go to next step.
5. Store fluid life index as indicated in scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM terminal C2. Turn ignition on. Voltage reading should be .1 volt. If reading is greater than .1 volt, go to next step. If reading is less than .1 volt, go to step 8).
6. Repair short to ground in HO2S high signal voltage.
7. Replace post-converter HO2S.
8. Replace PCM. Program replacement PCM using required equipment.

Check snapshot data for front long and rear long term fuel trim values. If both banks were rich, check for a condition that would cause a rich engine operation. Never solder HO2S wires.

DTC P0146 - HO2S CIRCUIT INSUFFICIENT ACTIVITY BANK 1, SENSOR 3 - POST-CONVERTER

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a .45 volt reference signal to the HO2S through the Bank 1 high signal circuit. When HO2S reaches operating temperature, it will generate a counter voltage that will vary based on the amount of oxygen in the exhaust. A lean exhaust will generate a low voltage and cause the reference voltage (.45 volt) to drop lower. A rich exhaust will generate a high voltage and cause the reference voltage to increase. If sensor cannot respond under the test conditions and generate a voltage greater than .61 volt or less than .31 volt, DTC will set.

Conditions for setting DTC

1. DTCs P0117, P0118, P0122 and P0123 not set.
2. TP sensor between 2.2-81.6 degrees.
3. Coolant temperature at 167°F (75°C) or greater.
4. Calculated throttle position switch open.
5. Engine speed between 800-3000 RPM.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Start and warm engine until coolant temperature reaches about 185°F (85°C) or greater. Using scan tool, select ENGINE 1 and note bank 1 sensor 3 voltage display for 30 seconds. If voltage remains .3-.6 volt, go to next step. If voltage does not remain .3-.6 volt, go to step 6).
3. Turn ignition off. Disconnect post-converter HO2S harness connector. Start engine. Using DVOM, check voltage between HO2S harness connector terminals "A" and "B". If voltage remains .3-.6 volt, diagnose using «DTC P0139»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0139-ho2s-slow-response) test. If voltage does not remain .3-.6 volt, go to next step.
4. Store fluid life index as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM connector C2. Using DVOM, check resistance between HO2S high signal circuit at PCM connector and HO2S harness connector terminal "B". If resistance is 5 ohms or less, go to next step. If not, go to step 8).
5. Check resistance between PCM connector C2 HO2S low signal circuit and HO2S harness connector terminal "A". If resistance is 5 ohms or greater, go to step 13). If resistance is less than 5 ohms, go to step 9).
6. Turn ignition on, with engine off. Check voltage between HO2S harness connector terminals "C" and "D". If voltage reading is 10.5 volts or greater, go to step 12). If not, go to next step.
7. Check voltage between oxygen sensor harness connector terminal "D" to ground. If reading is 10.5 volts or greater, go to step 10). If not, go to step 11).
8. Repair open in HO2S high signal circuit.
9. Repair open in HO2S low signal circuit.
10. Repair open in HO2S ground circuit.
11. Repair open or short to ground in HO2S ignition circuit.
12. Replace post-converter HO2S.
13. Check terminal contacts at PCM connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
14. Replace PCM. Program replacement PCM using required equipment.

Never solder oxygen sensor wires.

DTC P0147 - HO2S HEATER CIRCUIT BANK 1, SENSOR 3 (POST-CONVERTER)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test determines if the heating element in the post-converter oxygen sensor is working properly. Oxygen sensor voltage is produced when the sensor reaches operating temperature and when the oxygen content of the exhaust stream is different than that in the atmosphere. The heating element is energized through the ignition signal circuit, when ignition is turned on, allowing sensor to reach operating temperature quickly. This in turn allows the PCM to enter "closed loop" quicker. The voltage that the PCM measures on the oxygen sensor high and low inputs is called bias voltage. When bias voltage takes too long to vary (greater or less than bias voltage) after ignition is turned on, DTC will set.

Conditions for setting DTC

1. DTCs P0101, P0102, P0103, P0117, P0118 and P0146 not set.
2. ECT dropped at least 50°F (10°C) from end of the last ignition cycle to the beginning of this ignition cycle.
3. Average post-converter HO2S bias voltage between 352-546 millivolts.
4. Engine did not stall during test.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Disconnect post-converter oxygen sensor. Using DVOM, check voltage between sensor harness connector terminals "C" and "D". If voltage reading is greater than 10.5 volts, go to next step. If not, go to step 4).
3. Using jumper wire, jumper sensor connector terminal "D" to harness connector terminal "D". Set DVOM to amp scale. Connect DVOM in series with sensor connector terminal "C" to harness connector terminal "C". If DVOM reads between 0.9-1.5 amps, go to step 5). If not, go to next step.
4. Check voltage from harness connector terminal "D" to ground. If reading is 10.5 volts or greater, go to step 6). If not, go to step 7).
5. Using scan tool, select FREEZE FRAME data and operate vehicle under the same conditions which set the DTC. If DTC resets, diagnose using «DTC P0139»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0139-ho2s-slow-response) test. If DTC does not reset, fault is not present. See DIAGNOSTIC AIDS.
6. Repair open in HO2S ground circuit.
7. Repair open or short to ground in HO2S ignition signal circuit.
8. Replace HO2S.

An intermittent open in HO2S ignition signal circuit or ground circuit may cause DTC to set. A malfunctioning pre-converter HO2S may also set DTC. Never solder oxygen sensor wires.

DTC P0151 - HO2S CIRCUIT LOW VOLTAGE BANK 2, SENSOR 1 (FRONT)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a .45 volt reference signal to the HO2S through the Bank 2 high signal circuit. When HO2S is cold, less than 392°F (200°C), the sensor signal voltage will be about .45 volt and PCM will keep the system in "open loop".

Conditions for setting DTC

1. DTCs P0101, P0102, P0103, P0107, P0108, P0117, P0118, P0121, P0122, P0123, P0152 and P0154 not set.
2. TP sensor between 5.4-25 degrees.
3. Coolant temperature at 179°F (81.5°C) or greater.
4. Closed loop fuel control enabled.
5. Oxygen sensors ready.
6. Engine speed at 800 RPM or greater.
7. MAP sensor greater than 32 kPa.
8. Listed conditions met for 3 seconds.
9. DTC P0131 test runs and passes.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if «DTC P0154»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0154-ho2s-circuit-insufficient) is also present, diagnose this DTC first. If DTC P0154 is not present, go to next step.
3. If DTC was set because vehicle ran out of fuel, fault is not present. Clear DTC. If vehicle did not run out of fuel, go to next step.
4. Warm engine until coolant is at least 185°F (85°C). Using scan tool, note bank 2 sensor 1 voltage. If voltage remains less than .3 volt for 30 seconds or longer, go to next step. If not, fault is not present. See DIAGNOSTIC AIDS.
5. Ignition off. Unplug HO2S connector. Start engine. Check voltage between HO2S terminals "A" and "B". If voltage remains less than .3 volt for 30 seconds or longer, diagnose using «DTC P0153»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0153-ho2s-slow-response) test. If voltage does not remain .3 volt or less for 30 seconds or longer, go to next step.
6. Store fluid life index as indicated in scan tool. Turn ignition off and wait 30 seconds, disconnect PCM connector C2. Check resistance to ground at HO2S connector terminal "B". If resistance is greater than 10,000 ohms, go to next step. If not, go to step 8).
7. Check resistance between HO2S harness connector terminals "A" and "B". If resistance is 5 ohms or less, go to step 9). If not, go to step 10).
8. Repair short to ground in HO2S high signal circuit.
9. Repair HO2S high and low signal circuit shorted to each other.
10. Check terminal contact at PCM connector C2 HO2S high and low signal circuits. Repair as necessary. If okay, go to next step.
11. Replace PCM. Program replacement PCM using required equipment.

Check snapshot data for front long and rear long term fuel trim values. If both banks were lean, check for a condition that would cause lean engine operation. If only the front bank was lean, check for a condition that would cause only the front bank to be lean, such as an intermittent short to ground in HO2S high signal circuit. Never solder oxygen sensor wires.

DTC P0152 - HO2S CIRCUIT HIGH VOLTAGE BANK 2, SENSOR 1 (FRONT)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a .45 volt reference signal to the HO2S through the Bank 2 high signal circuit. When HO2S is cold, less than 392°F (200°C), the sensor signal voltage will be about .45 volt and PCM will keep the system in "open loop". When HO2S is warm, sensor will swing from rich to lean rapidly, at least one switch every 2 seconds, if PCM is in good control of air/fuel mixture.

If sensor stays at rich voltage for greater than 40 seconds during this test, DTC will set. DTC will also set when there is a sensor circuit fault giving a false rich indication or air/fuel ratio is actually rich due to a fuel control system fault.

Conditions for setting DTC

1. DTCs P0101, P0102, P0103, P0107, P0108, P0117, P0118, P0122, P0123, P0152 and P0154 not set.
2. TP sensor between 5.4-25 degrees.
3. Coolant temperature at 179°F (81.5°C) or greater.
4. Closed loop fuel control enabled.
5. Oxygen sensors ready.
6. Engine speed at 800 RPM or greater.
7. MAP sensor greater than 32 kPa.
8. Listed conditions met for 3 seconds.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if «DTC P0154»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0154-ho2s-circuit-insufficient) is also present, diagnose this DTC first. If DTC P0154 is not present, go to next step.
3. Start and warm engine until coolant temperature is at 185°F (85°C) or greater. Using scan tool, note front oxygen sensor voltage. If voltage remains at .6 volt or greater for 30 seconds or longer, go to next step. If not, fault is not present. See DIAGNOSTIC AIDS.
4. Turn engine off. Disconnect HO2S sensor harness connector. Start engine. Using DVOM, check voltage between sensor terminals "A" and "B". If voltage remains at greater than .6 volt for 30 seconds or longer, go to step 7). If not, go to next step.
5. Store fluid life index as indicated in scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM terminal C2. Turn ignition on. If reading is greater than .1 volt, go to next step. If not, go to step 8).
6. Repair short to ground in HO2S high signal voltage.
7. Replace post-converter HO2S.
8. Replace PCM. Program replacement PCM using required equipment.

Check snapshot data for front long and rear long term fuel trim values. If both banks were rich, check for a condition that would cause a rich engine operation. Never solder HO2S wires.

DTC P0153 - HO2S SLOW RESPONSE BANK 2, SENSOR 1 (FRONT)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a .45 volt reference signal to the HO2S through the Bank 2 high signal circuit. When HO2S is cold, less than 392F (200C), the sensor signal voltage will be about .45 volt and PCM will keep the system in "open loop". When HO2S is warm, sensor will swing from rich to lean rapidly, at least one switch every 2 seconds, if PCM is in good control of air/fuel mixture. If oxygen sensor is slow to respond to changes on exhaust oxygen content, DTC will set.

Conditions for setting DTC

1. DTCs P0117, P0118, P0121, P0122, P0123, P0155 and P1153 not set.
2. Test not completed this ignition cycle.
3. Low coolant level not present.
4. Ignition voltage between 9-16 volts.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. If you are referred here from another DTC, go to step 4). If not, go to next step.
3. If any other DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
4. Start and warm engine until coolant temperature reaches about 185°F (85°C) or greater. Using scan tool, select note bank 2 sensor 1 voltage display. Increase engine speed to 1200-2000 RPM for about 2 minutes. After 2 minutes HO2S reading should swing rapidly within a range of .3-.6 volt. If voltage reading is within range, go to step 6). If voltage reading is out of range, go to next step.
5. With engine running at 1200-2000 RPM, note LOOP STATUS on scan tool. If scan tool indicates "closed loop", go to step 10). If scan tool does not indicate "closed loop", go to step 9).
6. If HO2S voltage stays between range of .3-.6 volt longer than the time is swings out of range, go to step 9). If not, go to next step.
7. Check terminal contact for HO2S high and low signal voltage at PCM connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
8. Check terminal contact at oxygen sensor. Repair as necessary. If terminal contact is okay, go to next step.
9. Replace front HO2S. Check for possible sensor contamination such as, leaded fuel, incorrect gasket sealer or over rich operation.
10. Check for possible causes of extended rich or lean operation. Repair as necessary.

Never solder oxygen sensor wires.

DTC P0154 - HO2S CIRCUIT INSUFFICIENT ACTIVITY BANK 2, SENSOR 1 (FRONT)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a .45 volt reference signal to the HO2S through the Bank 2 high signal circuit. When HO2S reaches operating temperature, it will generate a counter voltage that will vary based on the amount of oxygen in the exhaust. A lean exhaust will generate a low voltage and cause the reference voltage (.45 volt) to drop lower. A rich exhaust will generate a high voltage and cause the reference voltage to increase. If sensor cannot respond under the test conditions and generate a voltage greater than .61 volt or less than .31 volt, DTC will set.

Conditions for setting DTC

1. DTCs P0117, P0118, P0121, P0122 and P0123 not set.
2. TP sensor between 1.0-81.6 degrees.
3. Coolant temperature at 163°F (72.5°C) or greater.
4. Calculated throttle position switch open.
5. Engine speed at 800 RPM or greater.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Start and warm engine until coolant temperature reaches about 185°F (85°C) or greater. Using scan tool, monitor bank 2 sensor 1 voltage display for 30 seconds. If voltage remains .3-.6 volt, go to next step. If voltage does not remain .3-.6 volt, go to step 6).
3. Turn ignition off. Disconnect front HO2S harness connector. Start engine. Using DVOM, check voltage between HO2S harness connector terminals "A" and "B". If voltage remains .3-.6 volt, diagnose using «DTC P0153»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0153-ho2s-slow-response) test. If voltage does not remain .3-.6 volt, go to next step.
4. Store fluid life index as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM connector C2. Using DVOM, check resistance between HO2S high signal circuit at PCM connector and HO2S harness connector terminal "B". If resistance is 5 ohms or less, go to next step. If not, go to step 8).
5. Check resistance between PCM connector C2 HO2S low signal circuit and HO2S harness connector terminal "A". If resistance is 5 ohms or less, go to next step. If not, go step 10).
6. Turn ignition on, with engine off. Check voltage between HO2S harness connector terminals "C" and "D"". If voltage is greater than 10.5 volts, go to next step. If not, go to step 8).
7. Using jumper wire, jumper oxygen sensor terminal "D" to oxygen harness connector terminal "D". Set DVOM to amp scale. Install DVOM in series between oxygen sensor terminal "C" and harness connector terminal "D". If reading is 0.9-1.5 amps, go to step 14). If reading is not as specified, go to step 13).
8. Check voltage between oxygen sensor harness connector terminal "D" to ground. If reading is 10.5 volts or greater, go to step 11). If reading is not 10.5 volts or greater, go to step 12).
9. Repair open in HO2S high signal circuit.
10. Repair open in HO2S low signal circuit.
11. Repair open in HO2S ground circuit.
12. Repair open or short to ground in HO2S ignition circuit.
13. Replace front HO2S.
14. Check terminal contacts at PCM connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
15. Replace PCM. Program replacement PCM using required equipment.

Never solder oxygen sensor wires.

DTC P0155 - HO2S HEATER CIRCUIT BANK 2, SENSOR 1 (FRONT)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test is used to determine if the heating element in the front oxygen sensor is operating properly. The sensor acts as a battery because it creates its own voltage once it reaches operating temperature. This voltage is produced when the oxygen content in the exhaust stream is different than that in the atmosphere.

Heating element is energized through the ignition circuit when ignition is on, allowing sensor to reach operating temperature quickly. This in turn allows PCM to enter into "closed loop" quicker.

When cold, the voltage that the PCM measures on the oxygen sensor high and low input circuits is called bias voltage. If it takes too long for oxygen sensor to vary the bias voltage within a specific time since ignition was turned on, DTC will set.

Conditions for setting DTC

1. DTCs P0101, P0102, P0103, P0107, P0117, P0118 and P0154 not set.
2. ECT dropped at least 50°F (10°C) from end of the last ignition cycle to the beginning of this ignition cycle.
3. Average heated HO2S bias voltage between 352-546 millivolts.
4. Engine did not stall during test.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Disconnect front HO2S harness connector. Using DVOM, check voltage between HO2S harness connector terminals "C" and "D". If voltage reading is 10.5 volts or greater, go to next step. If not, go to step 4).
3. Using jumper wire, jumper oxygen sensor terminal "D" to oxygen harness connector terminal "D". Set DVOM to amp scale. Install DVOM in series between oxygen sensor terminal "C" and harness connector terminal "D". Turn ignition on. If reading is 0.9-1.5 amps, go to step 5). If reading is not as specified, go to step 8).
4. Check voltage from HO2S harness connector terminal "D" to ground. If voltage reading is 10.5 volts or greater, go to step 6). If not, go to step 7).
5. Using scan tool, select FREEZE FRAME data and operate vehicle in the same conditions under which the DTC set. If DTC resets, diagnose using «DTC P0153»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0153-ho2s-slow-response) test. If DTC does not reset, fault is not present. See DIAGNOSTIC AIDS.
6. Repair open in HO2S ground circuit.
7. Repair open or short in ignition circuit to HO2S.
8. Replace HO2S.

An intermittent open in ignition or ground circuits to HO2S may cause DTC P0155 to set. A malfunctioning oxygen sensor heater could also cause DTC to set. Never solder oxygen sensor wires.

DTC P0171 - FUEL TRIM SYSTEM LEAN BANK 1

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM monitors the HO2S signal voltage and adjust fuel delivery based on signal voltage when system in "closed loop". A change made to fuel delivery will be indicated by the long and short term fuel trim values which can be monitored with a scan tool. Ideal fuel trim is about zero percent. If HO2S signal is indicating a lean condition, PCM will add fuel, resulting in a fuel trim greater than zero percent (100 percent maximum lean). If rich condition is detected, fuel trim values will be less than zero percent (-99 percent maximum rich), indicating that PCM is reducing the amount of fuel delivered. If an excessive lean condition is detected, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if any other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
3. Start and warm engine until coolant temperature reaches 185°F (85°C) or greater. Using scan tool, monitor LONG TERM BN. 1 and SHRT. TERM BN. 1 status. If either value is less than 95-98 percent, go to next step. If either value is greater than 95-98 percent, go to step 5).
4. Using FREEZE FRAME data, note conditions under which the was DTC set. Clear DTC and operate vehicle under the conditions that set DTC. Using scan tool, select NOT RUN SCC and TEST FAIL SCC to verify that this diagnostic test runs while duplicating test conditions. If this diagnostic test ran and failed this ignition cycle, go to next step. If this diagnostic test did not ran or did not fail in this ignition cycle, see DIAGNOSTIC AIDS.
5. If DTC P0174 is also present, go to next step. If DTC P0174 is not present, go to step 7).
6. Check vacuum hoses for splits, kinks and proper routing. Check throttle body, air induction system after MAF sensor, intake manifold, PCV and EGR valve for vacuum leaks. Check for contaminated fuel. Ensure PCM grounds are lean and tight. Check for mechanical failure. Repair as necessary. After repairs, go to step 8). If system is okay or no problem is found, see DIAGNOSTIC AIDS.
7. Inspect bank 1 for exhaust leaks, missing or loose exhaust hardware. Ensure HO2S is securely installed and wiring harness is not touching exhaust or ignition wires. Check for vacuum leaks that will only affect bank 1. Check for mechanical failure. If problem is found, go to next step. If system is okay or no problem is found, see DIAGNOSTIC AIDS.
8. Repair as necessary. After repairs, verify for proper operation of component(s).

If scan tool indicated that test ran and passed, fault is not present. If scan tool indicated that the test did not run, ensure that all the test conditions were met.

DTC P0172 - FUEL TRIM SYSTEM RICH BANK 1

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM monitors the HO2S signal voltage and adjust fuel delivery based on signal voltage when system in "closed loop". A change made to fuel delivery will be indicated by the long and short term fuel trim values which can be monitored with a scan tool. Ideal fuel trim is about zero percent. If HO2S signal is indicating a lean condition, PCM will add fuel, resulting in a fuel trim greater than zero percent (100 percent maximum lean). If rich condition is detected, fuel trim values will be less than zero percent (-99 percent maximum rich), indicating that PCM is reducing the amount of fuel delivered. If an excessive rich condition is detected, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if any other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
3. Start an warm engine until coolant temperature reaches 185°F (85°C) or greater. Using scan tool, monitor LONG TERM BN. 1 and SHRT. TERM BN. 1 status. If either values is less than -95 or -98 percent, go to next step. If either values is not less than -95 or -98 percent, go to step 5).
4. Using FREEZE FRAME data, note conditions under which the DTC was set. Clear DTC and operate vehicle under the conditions that set DTC. Using scan tool, select NOT RUN SCC and TEST FAIL SCC to verify that this diagnostic test runs while duplicating test conditions. If this diagnostic test ran and failed this ignition cycle, go to next step. If this diagnostic test did not run or did not fail in this ignition cycle, see DIAGNOSTIC AIDS.
5. If DTC P0175 is also present, go to next step. If DTC P0175 is not present, go to step 7).
6. Check for collapsed air intake duct, restricted air filter, improperly installed MAF sensor or for foreign objects blocking MAF sensor screen. Check for fuel in pressure regulator vacuum hose. If problem is found, go to step 8). If problem is not present, see DIAGNOSTIC AIDS.
7. Inspect for leaking injectors at bank 1. Repair as necessary. If injectors are okay, go to step 9).
8. Repair or replace any faulty items.
9. Replace rear HO2S.

If scan tool indicated that test ran and passed, fault is not present. If scan tool indicated that the test did not run, ensure that all the test conditions were met.

DTC P0174 - FUEL TRIM SYSTEM LEAN BANK 2

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM monitors the HO2S signal voltage and adjust fuel delivery based on signal voltage when system in "closed loop". A change made to fuel delivery will be indicated by the long and short term fuel trim values which can be monitored with a scan tool. Ideal fuel trim is about zero percent. If HO2S signal is indicating a lean condition, PCM will add fuel, resulting in a fuel trim greater than zero percent (100 percent maximum lean). If rich condition is detected, fuel trim values will be less than zero percent (-99 percent maximum rich), indicating that PCM is reducing the amount of fuel delivered. If an excessive lean condition is detected, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if any other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
3. Start an warm engine until coolant temperature reaches 185°F (85°C) or greater. Using scan tool, monitor LONG TERM BN. 1 and SHRT. TERM BN. 1 status. If either values are greater than 95-98 percent, go to next step. If either values is less than 95-98 percent, go to step 5).
4. Using FREEZE FRAME data, note conditions under which the DTC set. Clear DTC and operate vehicle under the conditions that set DTC. Using scan tool, select NOT RUN SCC and TEST FAIL SCC to verify that this diagnostic test runs while duplicating test conditions. If this diagnostic test ran and failed this ignition cycle, go to next step. If this diagnostic test did not run or did not fail in this ignition cycle, see DIAGNOSTIC AIDS.
5. If DTC P0171 is also present, go to next step. If DTC P0171 is not present, go to step 7).
6. Check vacuum hoses for splits, kinks and proper routing. Check throttle body, air induction system after MAF sensor, intake manifold, PCV and EGR valve for vacuum leaks. Check for contaminated fuel. Ensure PCM grounds are lean and tight. Check for mechanical failure. Repair as necessary. After repairs, go to step 8). If system is okay or no problem is found, see DIAGNOSTIC AIDS.
7. Inspect bank 2 for exhaust leaks, missing or loose exhaust hardware. Ensure HO2S is securely installed and wiring harness is not touching exhaust or ignition wires. Check for vacuum leaks that will only affect bank 2. Check for mechanical failure. If problem is found, go to next step. If system is okay or no problem is found, see DIAGNOSTIC AIDS.
8. Repair as necessary. After repairs, verify for proper operation of component(s).

If scan tool indicated that test ran and passed, fault is not present. If scan tool indicated that the test did not run, ensure that all the test conditions were met.

DTC P0175 - FUEL TRIM SYSTEM RICH BANK 2

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM monitors the HO2S signal voltage and adjust fuel delivery based on signal voltage when system in "closed loop". A change made to fuel delivery will be indicated by the long and short term fuel trim values which can be monitored with a scan tool. Ideal fuel trim is about zero percent. If HO2S signal is indicating a lean condition, PCM will add fuel, resulting in a fuel trim greater than zero percent (100 percent maximum lean). If rich condition is detected, fuel trim values will be less than zero percent (-99 percent maximum rich), indicating that PCM is reducing the amount of fuel delivered. If an excessive rich condition is detected, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if any other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
3. Start an warm engine until coolant temperature reaches 185°F (85°C) or greater. Using scan tool, monitor LONG TERM BN. 1 and SHRT. TERM BN. 1 status. If either values is less than -95 or -98 percent, go to next step. If not, go to step 5).
4. Using FREEZE FRAME data, note conditions under which the DTC set. Clear DTC and operate vehicle under the conditions that set DTC. Using scan tool, select NOT RUN SCC and TEST FAIL SCC to verify that this diagnostic test runs while duplicating test conditions. If this diagnostic test ran and failed this ignition cycle, go to next step. If this diagnostic test did not ran or did not fail in this ignition cycle, see DIAGNOSTIC AIDS.
5. If DTC P0172 is also present, go to next step. If DTC P0172 is not present, go to step 7).
6. Check for collapsed air intake duct, restricted air filter, improperly installed MAF sensor or for foreign objects blocking MAF sensor screen. Check for fuel in pressure regulator vacuum hose. If problem is found, go to step 8). If problem is not present, see DIAGNOSTIC AIDS.
7. Inspect for leaking injectors at bank 1. Repair as necessary. If injectors are okay, go to step 9).
8. Repair or replace any faulty components.
9. Replace rear HO2S.

If scan tool indicated that test ran and passed, fault is not present. If scan tool indicated that the test did not run, ensure that all the test conditions were met.

DTC P0201 - INJECTOR NO. 1 CONTROL CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

The PCM contains a General Field Effect Transistor Driver (GFD) that controls the 8 fuel injector drivers. The GFD is used to determine if there is a problem with any of the fuel injector circuits. The GFD has a fault line for each injector. The fault line goes high when an open, short to ground, or short to voltage is noticed in an injector circuit. DTC will set when the fault line for an injector is high.

Conditions for setting DTC

1. DTCs P0560 and P1376 not set.
2. Ignition voltage 10-16 volts.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC(s) P0204, P0206 and P0207 are also present. If these DTC(s) are present, go to next step. If these DTC(s) are not present, go to step 7).
3. Turn ignition off. Remove and inspect INJ 2 fuse. If fuse is faulty, go to next step. If fuse is okay, go to 6).
4. Disconnect fuel rail harness connector. Using DVOM, check resistance between fuel rail harness connector terminal "N" and ground. If resistance is greater than 5 ohms, go to next step. If resistance is not greater than 5 ohms, go to step 17).
5. Disconnect injector No. 1 harness connector. Check resistance between injector No. 1 harness connector terminal "A" and ground. Repeat test to injectors No. 4, 6 and 7. If resistance is less than 5 ohms on any of the circuits, go to step 18). If resistance is not less than 5 ohms on any of the circuits, go to step 19).
6. Disconnect fuel rail harness connector. Replace INJ 2 fuse. Turn ignition on. Using DVOM, check voltage between fuel rail harness connector terminal "N" and ground. If reading is 10 volts or greater, go to step 20). If reading is not 10 volts or greater, go to step 21).
7. Using scan tool, select DTC INFO then LAST TST. FAIL mode. If this DTC failed its last test, go to step 9). If this DTC does not show that it failed its last test, go to next step.
8. Clear DTC(s) and operate vehicle until DTC P0201 resets. If DTC P0201 resets, go to next step. If DTC P0201 does not reset, fault is not present.
9. Turn ignition off. Disconnect injector No. 1 harness connector. Turn ignition on. Check voltage between injector No. 1 harness connector terminal "A" and ground. If reading is 10 volts or greater, go to next step. If reading is not 10 volts or greater, go to step 22).
10. Reconnect injector No. 1 harness connector. Store fluid life reading as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between PCM harness connector C2 terminal No. 9 and ground. If reading is less than 10 volts, go to next step. If not, go to step 14).
11. Disconnect injector No. 1 harness connector. Check resistance between injector terminals "A" and "B". If resistance is greater than 8 ohms, go to next step. If not, go to step 27).
12. Check voltage between injector No. 1 harness connector terminal "A". If reading is .1 volt or less, go to next step. If reading is not .1 volt or less, go to step 23).
13. Check terminal contact at PCM connector C2. Repair as necessary. If terminal contact is okay, go to step 28).
14. Turn ignition off. Reconnect PCM connector C2. Disconnect fuel rail harness connector. Turn ignition on. Turn ignition on. Check voltage between injector harness terminal "A" and ground. DVOM should read 10 volts. If reading not as specified, go to next step. If reading is as specified, go to step 24).
15. Disconnect injector No. 1 harness connector. Check resistance between injector terminal "A" and ground. Resistance should be 10,000 ohms. If resistance is greater than 10,000 ohms, go to next step. If resistance is not greater than 10,000 ohms, go to step 25).
16. Check resistance between injector terminals "A" and "B". If resistance is greater than 25 ohms, go to step 27). If resistance is 25 ohms or less, go to step 26).
17. Repair short to ground between fuse and fuel rail connector.
18. Repair short to ground between fuel rail connector and injector connector that low resistance was measured on.
19. Replace INJ 2 fuse and retest for DTC(s).
20. Repair open in circuit between splice and duel rail connector.
21. Repair open in circuit between fuse B7 and fuel rail connector, or repair poor terminal contact at fuse.
22. Repair open in circuit between splice and injector No. 1.
23. Repair short to voltage between injector harness connector and PCM harness connector.
24. Repair open or short to ground in circuit between fuel rail connector and PCM.
25. Repair short to ground in circuit between fuel rail connector and injector No. 1.
26. Repair open in circuit between fuel rail connector and injector No. 1.
27. Replace fuel injector.
28. Replace PCM. Program replacement PCM using required equipment.

DTC P0202 - INJECTOR NO. 2 CONTROL CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

The PCM contains a General Field Effect Transistor Driver (GFD) that controls the 8 fuel injector drivers. The GFD is used to determine if there is a problem with any of the fuel injector circuits. The GFD has a fault line for each injector. The fault line goes high when an open, short to ground, or short to voltage is noticed in an injector circuit. DTC will set when the fault line for an injector is high.

Conditions for setting DTC

1. DTCs P0560 and P1376 not set.
2. Ignition voltage 10-16 volts.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC(s) P0203, P0205 and P0208 are also present. If these DTC(s) are present, go to next step. If these DTC(s) are not present, go to step 7).
3. Turn ignition off. Remove and inspect INJ 1 fuse. If fuse is faulty, go to next step. If fuse is okay, go to step 6).
4. Disconnect fuel rail harness connector. Using DVOM, check resistance between fuel rail harness connector terminal "P" and ground. If resistance is greater than 5 ohms, go to next step. If resistance is not greater than 5 ohms, go to step 17).
5. Disconnect injector No. 2 harness connector. Check resistance between injector No. 2 harness connector terminal "A" and ground. Repeat test to injectors No. 3, 5 and 8. If resistance is less than 5 ohms on any of the circuits, go to step 18). If resistance is not less than 5 ohms on any of the circuits, go to step 19).
6. Disconnect fuel rail harness connector. Replace INJ 1 fuse. Turn ignition on. Using DVOM, check voltage between fuel rail harness connector terminal "P" and ground. If reading is 10 volts or greater, go to step 20). If reading is not 10 volts or greater, go to step 21).
7. Using scan tool, select DTC INFO then LAST TST. FAIL mode. If this DTC failed its last test, go to step 9). If this DTC does not show that it failed its last test, go to next step.
8. Clear DTC(s) and operate vehicle until DTC P0202 resets. If DTC P0202 resets, go to next step. If DTC P0202 does not reset, fault is not present.
9. Turn ignition off. Disconnect injector No. 2 harness connector. Turn ignition on. Check voltage between injector No. 2 harness connector terminal "A" and ground. If reading is 10 volts or greater, go to next step. If reading is less than 10 volts, go to step 22).
10. Reconnect injector No. 2 harness connector. Store fluid life reading as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between PCM harness connector C2 terminal No. 10 and ground. If voltage is less than 10 volts, go to next step. If not, go to step 14).
11. Disconnect injector No. 2 harness connector. Check resistance between injector terminals "A" and "B". If resistance is greater than 8 ohms, go to next step. If not, go to step 27).
12. Check voltage between injector No. 2 harness connector terminal "B". If reading is .1 volt or less, go to next step. If reading is not .1 volt or less, go to step 23).
13. Check terminal contact at PCM connector C2. Repair as necessary. If terminal contact is okay, go to step 28).
14. Turn ignition off. Reconnect PCM connector C2. Disconnect fuel rail harness connector. Turn ignition on. Check voltage between injector harness terminal "A" and ground. Voltage should be 10 volts. If voltage not as specified, go to next step. If voltage is as specified, go to step 24).
15. Disconnect injector No. 2 harness connector. Check resistance between injector terminal "B" and ground. If resistance is greater than 10,000 ohms, go to next step. If resistance is not greater than 10,000 ohms, go to step 25).
16. Check resistance between injector terminals "A" and "B". If resistance is greater than 25 ohms, go to step 27). If resistance is less than 25 ohms, go to step 26).
17. Repair short to ground between fuse and fuel rail connector.
18. Repair short to ground between fuel rail connector and injector connector that low resistance was measured on.
19. Replace fuse and retest for DTC(s).
20. Repair open in circuit between splice and fuel rail connector.
21. Repair open in circuit between fuse and fuel rail connector, or repair poor terminal contact at fuse.
22. Repair open in circuit between splice and injector No. 1.
23. Repair short to voltage between injector harness connector and PCM harness connector.
24. Repair open or short to ground in circuit between fuel rail connector and PCM.
25. Repair short to ground in circuit between fuel rail connector and injector No. 1.
26. Repair open in circuit between fuel rail connector and injector No. 1.
27. Replace fuel injector.
28. Replace PCM. Program replacement PCM using required equipment.

DTC P0203 - INJECTOR NO. 3 CONTROL CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

The PCM contains a General Field Effect Transistor Driver (GFD) that controls the 8 fuel injector drivers. The GFD is used to determine if there is a problem with any of the fuel injector circuits. The GFD has a fault line for each injector. The fault line goes high when an open, short to ground, or short to voltage is noticed in an injector circuit. DTC will set when the fault line for an injector is high.

Conditions for setting DTC

1. DTCs P0560 and P1376 not set.
2. Ignition voltage between 10-16 volts.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC(s) P0202, P0205 and P0208 are also present. If these DTC(s) are present, diagnose using «DTC P0202»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0202-injector-no-2) test. If these DTC(s) are not present, go to next step.
3. Using scan tool, select DTC INFO then LAST TST. FAIL mode. If this DTC failed its last test, go to step 5). If this DTC does not show that it failed its last test, go to next step.
4. Clear DTC(s) and operate vehicle until DTC P0203 resets. If DTC P0203 resets, go to next step. If DTC P0203 does not reset, fault is not present.
5. Turn ignition off. Disconnect injector No. 3 harness connector. Turn ignition on. Check voltage between injector No. 3 harness connector terminal "A" and ground. If voltage reading is 10 volts or greater, go to next step. If not, go to step 13).
6. Reconnect injector No. 3 harness connector. Store fluid life reading as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between PCM harness connector C2 terminal No. 12 and ground. If voltage is greater than 10 volts, go to next step. If voltage is not greater than 10 volts, go to step 10).
7. Disconnect injector No. 3 harness connector. Check resistance between injector terminals "A" and "B". If resistance is greater than 8 ohms, go to next step. If not, go to step 18).
8. Check voltage between injector No. 3 harness connector terminal "B". If reading is .1 volt or less, go to next step. If not, go to step 14).
9. Check terminal contact at PCM connector C2. Repair as necessary. If terminal contact is okay, go to step 19).
10. Turn ignition off. Reconnect PCM connector C2. Disconnect fuel rail harness connector. Turn ignition on. Turn ignition on. Check voltage between injector harness terminal "D" and ground. If voltage is less than 10 volts, go to next step. If not, go to step 15).
11. Disconnect injector No. 3 harness connector. Check resistance between injector terminal "A" and ground. If resistance is greater than 10,000 ohms, go to next step. If resistance is less than 10,000 ohms, go to step 16).
12. Check resistance between injector terminals "A" and "B". If resistance is greater than 25 ohms, go to step 18). If not, go to step 17).
13. Repair open in circuit between splice and injector No. 3.
14. Repair short to voltage between injector harness connector and PCM harness connector.
15. Repair open or short to ground in circuit between fuel rail connector and injector No. 3.
16. Repair short to ground in circuit between fuel rail connector and injector No. 3.
17. Repair open in circuit between fuel rail connector and injector No. 3.
18. Replace fuel injector.
19. Replace PCM. Program replacement PCM using required equipment.

DTC P0204 - INJECTOR NO. 4 CONTROL CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

The PCM contains a General Field Effect Transistor Driver (GFD) that controls the 8 fuel injector drivers. The GFD is used to determine if there is a problem with any of the fuel injector circuits. The GFD has a fault line for each injector. The fault line goes high when an open, short to ground, or short to voltage is noticed in an injector circuit. DTC will set when the fault line for an injector is high.

Conditions for setting DTC

1. DTCs P0560 and P1376 not set.
2. Ignition voltage 10-16 volts.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC(s) P0201, P0206 and P0207 are also present. If these DTC(s) are present, diagnose using «DTC P0201»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0201-injector-no-1) test. If these DTC(s) are not present, go to next step.
3. Using scan tool, select DTC INFO then LAST TST. FAIL mode. If this DTC failed its last test, go to step 5). If this DTC does not show that it failed its last test, go to next step.
4. Clear DTC(s) and operate vehicle until DTC P0204 resets. If DTC P0204 resets, go to next step. If DTC P0204 does not reset, fault is not present.
5. Turn ignition off. Disconnect injector No. 4 harness connector. Turn ignition on. Check voltage between injector No. 4 harness connector terminal "A" and ground. If reading is 10 volts or greater, go to next step. If not, go to step 13).
6. Reconnect injector No. 3 harness connector. Store fluid life reading as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between PCM harness connector C2 terminal No. 13 and ground. If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, go to step 10).
7. Disconnect injector No. 4 harness connector. Check resistance between injector terminals "A" and "B". If resistance is greater than 8 ohms, go to next step. If resistance is less than 8 ohms, go to step 18).
8. Check voltage between injector No. 4 harness connector terminal "B". If reading is .1 volt or less, go to next step. If reading is greater than .1 volt, go to step 14).
9. Check terminal contact at PCM connector C2. Repair as necessary. If terminal contact is okay, go to step 19).
10. Turn ignition off. Reconnect PCM connector C2. Disconnect fuel rail harness connector. Turn ignition on. Turn ignition on. Check voltage between injector harness terminal "E" and ground. If voltage is less than 10 volts, go to next step. If not, go to step 15).
11. Disconnect injector No. 4 harness connector. Check resistance between injector terminal "A" and ground. If resistance is greater than 10,000 ohms, go to next step. If resistance is less than 10,000 ohms, go to step 16).
12. Check resistance between injector terminals "A" and "B". If resistance is greater than 25 ohms, go to step 18). If resistance is less than 25 ohms, go to step 17).
13. Repair open in circuit between splice and injector No. 4.
14. Repair short to voltage between injector harness connector and PCM harness connector.
15. Repair open or short to ground in circuit between fuel rail connector and injector No. 4.
16. Repair short to ground in circuit between fuel rail connector and injector No. 4.
17. Repair open in circuit between fuel rail connector and injector No. 4.
18. Replace fuel injector.
19. Replace PCM. Program replacement PCM using required equipment.

DTC P0205 - INJECTOR NO. 5 CONTROL CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

The PCM contains a General Field Effect Transistor Driver (GFD) that controls the 8 fuel injector drivers. The GFD is used to determine if there is a problem with any of the fuel injector circuits. The GFD has a fault line for each injector. The fault line goes high when an open, short to ground, or short to voltage is noticed in an injector circuit. DTC will set when the fault line for an injector is high.

Conditions for setting DTC

1. DTCs P0560 and P1376 not set.
2. Ignition voltage 10-16 volts.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC(s) P0202, P0203 and P0208 are also present. If these DTC(s) are present, diagnose using «DTC P0202»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0202-injector-no-2) test. If these DTC(s) are not present, go to next step.
3. Using scan tool, select DTC INFO then LAST TST. FAIL mode. If this DTC failed its last test, go to step 5). If this DTC does not show that it failed its last test, go to next step.
4. Clear DTC(s) and operate vehicle until DTC P0205 resets. If DTC P0205 resets, go to next step. If DTC P0205 does not reset, fault is not present.
5. Turn ignition off. Disconnect injector No. 5 harness connector. Turn ignition on. Check voltage between injector No. 5 harness connector terminal "A" and ground. If voltage is 10 volts or greater, go to next step. If not, go to step 13).
6. Reconnect injector No. 5 harness connector. Store fluid life reading as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between PCM harness connector C2 terminal No. 17 and ground. If voltage is greater than 10 volts, go to next step. If not, go to step 10).
7. Disconnect injector No. 5 harness connector. Check resistance between injector terminals "A" and "B". If resistance is greater than 8 ohms, go to next step. If not, go to step 18).
8. Check voltage between injector No. 5 harness connector terminal "B". If voltage is .1 volt or less, go to next step. If not, go to step 14).
9. Check terminal contact at PCM connector C2. Repair as necessary. If terminal contact is okay, go to step 19).
10. Turn ignition off. Reconnect PCM connector C2. Disconnect fuel rail harness connector. Turn ignition on. Turn ignition on. Check voltage between injector harness terminal "T" and ground. If voltage is less than 10 volts, go to next step. If not, go to step 15).
11. Disconnect injector No. 5 harness connector. Check resistance between injector terminal "A" and ground. If resistance is greater than 10,000 ohms, go to next step. If not, go to step 16).
12. Check resistance between injector terminals "A" and "B". If resistance is greater than 25 ohms, go to step 18). If not, go to step 17).
13. Repair open in circuit between splice and injector No. 5.
14. Repair short to voltage between injector harness connector and PCM harness connector.
15. Repair open or short to ground in circuit between fuel rail connector and injector No. 5.
16. Repair short to ground in circuit between fuel rail connector and injector No. 5.
17. Repair open in circuit between fuel rail connector and injector No. 5.
18. Replace fuel injector.
19. Replace PCM. Program replacement PCM using required equipment.

DTC P0206 - INJECTOR NO. 6 CONTROL CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

The PCM contains a General Field Effect Transistor Driver (GFD) that controls the 8 fuel injector drivers. The GFD is used to determine if there is a problem with any of the fuel injector circuits. The GFD has a fault line for each injector. The fault line goes high when an open, short to ground, or short to voltage is noticed in an injector circuit. DTC will set when the fault line for an injector is high.

Conditions for setting DTC

1. DTCs P0560 and P1376 not set.
2. Ignition voltage 10-16 volts.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC(s) P0201, P0204 and P0207 are also present. If these DTC(s) are present, diagnose using «DTC P0201»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0201-injector-no-1) test. If these DTC(s) are not present, go to next step.
3. Using scan tool, select DTC INFO then LAST TST. FAIL mode. If this DTC failed its last test, go to step 5). If this DTC does not show that it failed its last test, go to next step.
4. Clear DTC(s) and operate vehicle until DTC P0206 resets. If DTC P0206 resets, go to next step. If DTC P0206 does not reset, fault is not present.
5. Turn ignition off. Disconnect injector No. 6 harness connector. Turn ignition on. Check voltage between injector No. 6 harness connector terminal "A" and ground. If reading is 10 volts or greater, go to next step. If not, go to step 13).
6. Reconnect injector No. 6 harness connector. Store fluid life reading as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between PCM harness connector C2 terminal No. 18 and ground. If voltage is greater than 10 volts, go to next step. If not, go to step 10).
7. Disconnect injector No. 6 harness connector. Check resistance between injector terminals "A" and "B". If resistance is greater than 8 ohms, go to next step. If not, go to step 18).
8. Check voltage between injector No. 6 harness connector terminal "B". If voltage is .1 volt or less, go to next step. If not, go to step 14).
9. Check terminal contact at PCM connector C2. Repair as necessary. If terminal contact is okay, go to step 19).
10. Turn ignition off. Reconnect PCM connector C2. Disconnect fuel rail harness connector. Turn ignition on. Turn ignition on. Check voltage between injector harness terminal "U" and ground. If voltage is less than 10 volts, go to next step. If not, go to step 15).
11. Disconnect injector No. 6 harness connector. Check resistance between injector terminal "A" and ground. If resistance is greater than 10,000 ohms, go to next step. If not, go to step 16).
12. Check resistance between injector terminals "A" and "B". If resistance is greater than 25 ohms, go to step 18). If not, go to step 17).
13. Repair open in circuit between splice and injector No. 6.
14. Repair short to voltage between injector harness connector and PCM harness connector.
15. Repair open or short to ground in circuit between fuel rail connector and injector No. 6.
16. Repair short to ground in circuit between fuel rail connector and injector No. 6.
17. Repair open in circuit between fuel rail connector and injector No. 6.
18. Replace fuel injector.
19. Replace PCM. Program replacement PCM using required equipment.

DTC P0207 - INJECTOR NO. 7 CONTROL CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

The PCM contains a General Field Effect Transistor Driver (GFD) that controls the 8 fuel injector drivers. The GFD is used to determine if there is a problem with any of the fuel injector circuits. The GFD has a fault line for each injector. The fault line goes high when an open, short to ground, or short to voltage is noticed in an injector circuit. DTC will set when the fault line for an injector is high.

Conditions for setting DTC

1. DTCs P0560 and P1376 not set.
2. Ignition voltage 10-16 volts.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC(s) P0201, P0204 and P0206 are also present. If these DTC(s) are present, diagnose using «DTC P0201»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0201-injector-no-1) test. If these DTC(s) are not present, go to next step.
3. Using scan tool, select DTC INFO then LAST TST. FAIL mode. If this DTC failed its last test, go to step 5). If this DTC does not show that it failed its last test, go to next step.
4. Clear DTC(s) and operate vehicle until DTC P0207 resets. If DTC P0207 resets, go to next step. If DTC P0207 does not reset, fault is not present.
5. Turn ignition off. Disconnect injector No. 7 harness connector. Turn ignition on. Check voltage between injector No. 7 harness connector terminal "A" and ground. If reading is 10 volts or greater, go to next step. If not, go to step 13).
6. Reconnect injector No. 7 harness connector. Store fluid life reading as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between PCM harness connector C2 terminal No. 11 and ground. If voltage is greater than 10 volts, go to next step. If not, go to step 10).
7. Disconnect injector No. 7 harness connector. Check resistance between injector terminals "A" and "B". If resistance is greater than 8 ohms, go to next step. If not, go to step 18).
8. Check voltage between injector No. 7 harness connector terminal "B". If reading is .1 volt or less, go to next step. If not, go to step 14).
9. Check terminal contact at PCM connector C2. Repair as necessary. If terminal contact is okay, go to step 19).
10. Turn ignition off. Reconnect PCM connector C2. Disconnect fuel rail harness connector. Turn ignition on. Turn ignition on. Check voltage between injector harness terminal "C" and ground. If voltage is less than 10 volts, go to next step. If not, go to step 15).
11. Disconnect injector No. 7 harness connector. Check resistance between injector terminal "A" and ground. If resistance is greater than 10,000 ohms, go to next step. If not, go to step 16).
12. Check resistance between injector terminals "A" and "B". If resistance is greater than 25 ohms, go to step 18). If not, go to step 17).
13. Repair open in circuit between splice and injector No. 7.
14. Repair short to voltage between injector harness connector and PCM harness connector.
15. Repair open or short to ground in circuit between fuel rail connector and injector No. 7.
16. Repair short to ground in circuit between fuel rail connector and injector No. 7.
17. Repair open in circuit between fuel rail connector and injector No. 7.
18. Replace fuel injector.
19. Replace PCM. Program replacement PCM using required equipment.

DTC P0208 - INJECTOR NO. 8 CONTROL CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

The PCM contains a General Field Effect Transistor Driver (GFD) that controls the 8 fuel injector drivers. The GFD is used to determine if there is a problem with any of the fuel injector circuits. The GFD has a fault line for each injector. The fault line goes high when an open, short to ground, or short to voltage is noticed in an injector circuit. DTC will set when the fault line for an injector is high.

Conditions for setting DTC

1. DTCs P0560 and P1376 not set.
2. Ignition voltage 10-16 volts.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC(s) P0202, P0203 and P0205 are also present. If these DTC(s) are present, diagnose using «DTC P0202»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0202-injector-no-2) test. If these DTC(s) are not present, go to next step.
3. Using scan tool, select DTC INFO then LAST TST. FAIL mode. If this DTC failed its last test, go to step 5). If this DTC does not show that it failed its last test, go to next step.
4. Clear DTC(s) and operate vehicle until DTC P0208 resets. If DTC P0208 resets, go to next step. If DTC P0208 does not reset, fault is not present.
5. Turn ignition off. Disconnect injector No. 8 harness connector. Turn ignition on. Check voltage between injector No. 8 harness connector terminal "A" and ground. If reading is 10 volts or greater, go to next step. If not, go to step 13).
6. Reconnect injector No. 8 harness connector. Store fluid life reading as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between PCM harness connector C2 terminal No. 22 and ground. If voltage reading is 10 volts or greater, go to next step. If not, go to step 10).
7. Disconnect injector No. 8 harness connector. Check resistance between injector terminals "A" and "B". If resistance is greater than 8 ohms, go to next step. If not, go to step 18).
8. Check voltage between injector No. 8 harness connector terminal "B". If reading is .1 volt or less, go to next step. If not, go to step 14).
9. Check terminal contact at PCM connector C2. Repair as necessary. If terminal contact is okay, go to step 19).
10. Turn ignition off. Reconnect PCM connector C2. Disconnect fuel rail harness connector. Turn ignition on. Turn ignition on. Check voltage between injector harness terminal "V" and ground. If voltage is less than 10 volts, go to next step. If voltage is as specified, go to step 15).
11. Disconnect injector No. 8 harness connector. Check resistance between injector terminal "A" and ground. If resistance is greater than 10,000 ohms, go to next step. If not, go to step 16).
12. Check resistance between injector terminals "A" and "B". If resistance is greater than 25 ohms, go to step 18). If not, go to step 17).
13. Repair open in circuit between splice and injector No. 8.
14. Repair short to voltage between injector harness connector and PCM harness connector.
15. Repair open or short to ground in circuit between fuel rail connector and injector No. 8.
16. Repair short to ground in circuit between fuel rail connector and injector No. 8.
17. Repair open in circuit between fuel rail connector and injector No. 8.
18. Replace fuel injector.
19. Replace PCM. Program replacement PCM using required equipment.

DTC P0231 - FUEL PUMP FEEDBACK CIRCUIT LOW VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

Fuel pump is powered by fuel pump relay. PCM energizes the fuel pump relay for 2 seconds at ignition on, to provide fuel pressure for starting. After the 2 second fuel pump prime, PCM will not power fuel pump until 4X reference pulses are received, indicating that the engine is cranking or running. PCM monitors voltage in the fuel pump feedback circuit to select fuel pump voltage supply faults. DTC will set when PCM sees the fuel pump is not energized (2 volts or less on feedback) with engine cranking or running.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition off. Turn ignition on for 5 seconds. After 5 seconds, attempt to start engine. If engine starts and runs, go to next step. If engine does not start or starts but dies, go to step 7).
3. Using scan tool, note DTC status condition. If DTC failed in this ignition cycle, go to next step. If DTC did not fail in this ignition cycle, fault is not present. See DIAGNOSTIC AIDS.
4. With engine still running, note FP. VOLT FEEDBACK on scan tool. If voltage is greater than 2 volts, go to step 25). If not, go to next step.
5. Store fluid life as indicated on scan tool. Turn ignition off and wait 30 seconds, then removed fuel pump relay. Disconnect PCM harness connector C1. Using DVOM, check resistance between fuel pump relay harness connector terminal No. 87 and fuel pump feedback circuit at PCM harness connector. If resistance is 5 ohms or less, go to step 25). If not, go to next step.
6. Repair open in circuit between PCM and splice or check for poor terminal contact at PCM connector C1.
7. Check fuel pump fuse, located in rear fuse block. If fuse is okay, go to next step. If fuse is faulty, go to step 18).
8. Remove fuel pump relay. Turn ignition on. Using DVOM, check voltage to ground at relay harness connector terminal No. 30. If voltage is 10 volts or greater, go to next step. If not, go to step 23).
9. Check voltage between fuel pump harness connector terminals No. 30 and No. 86. If voltage is 10 volts or greater, go to next step. If not, go to step 24).
10. Connect a jumper between fuel pump harness connector terminals No. 30 and 87. If fuel pump operates, go to next step. If fuel pump does not operate, go to step 15).
11. Turn ignition off. Connect DVOM between fuel pump relay harness connector terminals No. 85 and No. 86. Wait 10 seconds, then turn ignition on and check voltage reading within 2 seconds after turning on ignition. If voltage is 10 volts or greater, go to next step. If not, go to step 13).
12. Replace fuel pump relay.
13. Store fluid life as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Using DVOM, check resistance between fuel pump relay control circuit at PCM harness connector and relay harness connector terminal No. 85. If resistance is 5 ohms or less, go to step 25). If not, go to next step.
14. Repair open in circuit between PCM harness connector and relay harness connector.
15. Using scan tool, note FP. VOLT FEEDBACK reading. If reading is 10 volts or greater, go to next step. If not, go to step 17).
16. Check for open in circuit between fuel pump and splice. Repair as necessary. If circuit is okay, go to step 22).
17. Check for open in circuit between fuel pump and splice.
18. Turn ignition off. Remove fuel pump relay. Using DVOM, check resistance between fuel pump harness connector terminal No. 30 and ground. If resistance is 2 ohms or greater, go to step 20). If not, go to next step.
19. Repair short to ground between fuel pump fuse and relay.
20. Store fluid life as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector C1. Disconnect fuel pump connector. Check resistance to ground at fuel pump relay harness connector terminal No. 87. If resistance is greater than 2 ohms, go to step 22). If not, go to next step.
21. Repair short to ground between PCM connector C1, fuel pump connector, fuel pump relay or a shorted fuel pump.
22. Check fuel pump ground circuit for cause of no-start condition. If ground circuit is okay, perform basic fuel pressure check.
23. Repair open in circuit between fuse and relay.
24. Repair open in ground circuit. If circuit is okay, check for poor ground connection.
25. Check terminal contact at PCM connector C1 fuel pump feedback circuit and PCM connector C2 fuel pump relay control circuit. Repair as necessary. If terminal contact is okay, go to next step.
26. Replace PCM. Program replacement PCM using required equipment.

If DTC sets without a driveability complaint, check for open circuit between splice and PCM or poor PCM terminal contact. If a complaint did not exist, check for poor relay contact, relay ground, etc.

DTC P0232 - FUEL PUMP FEEDBACK CIRCUIT HIGH VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

Fuel pump is powered by fuel pump relay. PCM energizes the fuel pump relay for 2 seconds at ignition on, to provide fuel pressure for starting. After the 2 second fuel pump prime, PCM will not power fuel pump until 4X reference pulses are received, indicating that the engine is cranking or running. PCM monitors voltage in the fuel pump feedback circuit to select fuel pump voltage supply faults. DTC will set when PCM sees the fuel pump is not energized (2 volts or less on feedback) with engine cranking or running.

Conditions for setting DTC

1. DTCs P0117, P0118 and P0322 not set.
2. Coolant temperature at 122°F (50°C) or greater.
3. No reference pulses detected since key on.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on for 15 seconds. Using scan tool, note FP. VOLT FEEDBACK reading. If voltage is greater than 7 volts, go to next step. If not, fault is not present.
3. Remove fuel pump relay. If scan tool displays greater than 7 volts, go to next step. If not, go to step 6).
4. Store fluid life as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector C1. Turn ignition on. Check voltage to ground at PCM harness connector C1 fuel pump feedback circuit. If voltage is 7 volts or less, go to step 11). If not, go to next step.
5. Check for loose or poor fuel pump ground connection. Repair as necessary. If ground connection is okay, go to step 8).
6. Turn ignition off. Wait 10 seconds. Using DVOM, check voltage between fuel pump relay harness connector terminals No. 85 and No. 86. Turn ignition on and note DVOM reading. If voltage reading remains at 12 volts for 10 seconds, go to next step. If voltage reading does not stay at 12 volts for 10 seconds, go to step 9).
7. Store fluid life as indicated on scan tool. Turn ignition off and wait 30 seconds. Disconnect PCM connector C2. Turn ignition on. Check voltage between ground and PCM harness connector fuel pump relay control circuit. If voltage is greater than zero volts, go to step 10). If not, go to step 11).
8. Repair short to voltage in fuel pump feedback circuit.
9. Replace fuel pump.
10. Repair short to voltage in fuel pump relay control circuit.
11. Check terminal contact at PCM harness connector C1 fuel pump feedback circuit. Repair as necessary. If terminal contact is okay, go to next step.
12. Replace PCM. Program replacement PCM using required equipment.

DTC could set due to sluggish or intermittently stuck fuel pump relay.

DTC P0300-P0308 - ENGINE MISFIRE DETECTED

Note. DTC P0300 is set when the ECM recognizes a general misfire in the engine. If the ECM determines the cylinder causing the misfire it will set a specific DTC P0301-P0308, to indicate the number of the cylinder causing the misfire. If a DTC P0301-P0308 is retrieved, use this procedure to diagnose the misfire condition in the indicated cylinder.

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test is used to detect misfires in any cylinder. A misfire occurs when there is a complete lack of combustion in the cylinder. A misfire will cause a fluctuation in crankshaft revolution speed. PCM uses the time between 4X reference pulses to determine when these fluctuations occur. At lower speeds, fluctuations in crankshaft speed are measured each reference pulse to detect misfire. At higher engine speeds, fluctuations in crankshaft speed are monitored over 2 engine revolutions and fluctuations in crankshaft speed at each half revolution are compared to compute a balance number. The 4X reference pulses originate in the ignition control module and vary with RPM.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check for any other DTC(s) present. If other DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
3. Start and idle engine. Using scan tool, observe MISFIRE CUR. counters in the misfire data list (there are 8 counters, one for each cylinder). If any of the counters are incrementing, go to next step. If counters are not incrementing, go to step 15).
4. Turn ignition off. Connect Spark Tester (ST-125) to ignition wire(s) that indicated a misfire. Ground the companion cylinder(s) plug wire. Start engine. If spark is present and consistent at spark tester, go to next step. If spark is not present or is intermittent at spark tester, go to step 9).
5. Turn ignition off. Remove and check spark plug from affected cylinder(s). If spark plug is okay (not oil or coolant fouled), diagnose fuel injector. See the SYSTEM/COMPONENT TESTS article. If spark plug is fouled, go to next step.
6. If spark plug is oil or coolant fouled, check engine for mechanical problems. If spark plug is not fouled, go to next step.
7. If spark plug is cracked or improperly gapped, go to next step. If spark plug is okay, diagnose fuel injector(s). See the SYSTEM/COMPONENT TESTS article.
8. Replace or re-gap spark plug.
9. Turn ignition off. Using DVOM, check resistance of each affected spark plug wire. If resistance is less than 15,000 ohms, go to next step. If not, go to step 13).
10. Remove affected coil(s). Check for carbon tracking on coil. If carbon tracking is not present, go to next step. If carbon tracking is present, go to step 12).
11. Switch position of coils at affected cylinder. Start and idle engine. If spark is present and consistent on spark tester, go to next step. If spark is not present or not consistent, go to step 14).
12. Turn ignition off. Replace faulty ignition coil and spark plug wire.
13. Replace spark plug wire.
14. Replace ignition control module.
15. Turn ignition on, with engine off. Review DTC P0300 snapshot data. Note conditions that the vehicle was operating when DTC was set and operate vehicle under the same condition. Using scan tool, observe MISFIRE CUR. counters in the misfire data list. If any of the counters are incrementing, repeat step 4). if counters are not incrementing, go to next step.
16. Turn ignition on, with engine off. Using scan tool, observe MISFIRE HIST. counters in the misfire data list. If more than 3 cylinders show a high misfire rate, go to step 18). If less than 3 cylinders show a high misfire rate, go to next step.
17. Note cylinder that shows a higher number of misfire. Check affected cylinder for damaged or high resistance spark plug wire, vacuum leak, damaged spark plug, etc. Repair as necessary. If no problems are found, see DIAGNOSTIC AIDS.
18. Check engine for proper vent operation, vacuum leaks or intermittent rich or lean condition. Repair as necessary. If not problems are found, see DIAGNOSTIC AIDS.

If more than one cylinder showed a history code of misfire, look for something in common between the cylinders such as, shared coils, etc. Also, check for vacuum leaks at the affected cylinder.

If fault cannot be duplicated, mist secondary ignition system with water and operate vehicle under conditions that set the DTC.

DTC P0322 - IGNITION CONTROL (IC) MODULE 4X REFERENCE CIRCUIT NO FREQUENCY

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM check for camshaft pulses being received without 4X reference pulses.

Conditions for setting DTC

1. DTCs P0340 and P1376 not set.
2. A CAM sensor signal has been received in the last 4 seconds.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if «DTC P1376»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p1376-ignition-ground-circuit) is also present. If DTC P1376 is present, diagnose this DTC first. If DTC P1376 is not present, go to next step.
3. Start and idle engine. Using scan tool, select DTC INFO then FAIL THIS IGN. in DTC mode. If DTC P0322 is indicated as current, go to next step. If DTC P0322 does not indicate as current, go to step 9).
4. Store fluid life data as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector C2. Disconnect Ignition Control (IC) module harness connector C4. Using DVOM, check resistance between ground and IC module harness connector fuel control circuit terminal. If resistance is 10,000 ohms or greater, go to next step. If not, go to step 9).
5. Check resistance between PCM harness connector fuel control circuit terminal and IC module harness connector C4 fuel control circuit terminal. If resistance is 5 ohms or less, go to next step. If not, go to step 13).
6. Turn ignition on. Check voltage to ground at IC module harness connector C4 fuel control circuit terminal. If voltage reading is .5 volt or less, go to next step. If not, go to step 14).
7. Reconnect IC module harness connector C4. Check voltage to ground at PCM harness connector C4 cam signal circuit terminal. If voltage is 4.1 volts or greater, go to next step. If not, go to step 15).
8. Turn ignition off. Reconnect PCM harness connector C2. Using 6-Pin IC Module Diagnostic Jumpers, jumper the following IC module connector C4 terminals to the following module terminals: C4 Terminal "A" To Module Pin "A" C4 Terminal "B" To Module Pin "B" C4 Terminal "C" To Module Pin "C" C4 Terminal "D" To Module Pin "D" C4 Terminal "E" To Module Pin "E" C4 Terminal "F" To Module Pin "F" Set DVOM to amp scale. Connect DVOM between terminal "C" jumper. Start engine and check frequency in terminal "C" jumper. If frequency is 30-100 Hz, go to step 16). If not, go to step 15).
9. Using DVOM, check FAILURE REC. for DTC P0322 and note MAP value when DTC was set. If MAP value is greater than 80 kPa, go to next step. If not, go to step 11).
10. Check for intermittent short to voltage or for Electromagnetic Interference (EMI) on cam sensor wires. EMI can be caused by wiring being too close to spark plug wires or high power transmitters operating within vicinity. DTC can also be set by battery charger. Repair or correct problem as necessary. If circuits are okay and if the other conditions are not present, fault is not present.
11. Check for intermittent open or short in fuel control circuit between PCM and IC module connectors. Also check circuit to DIS fuse. Repair as necessary.
12. Repair short to ground in fuel control circuit.
13. Repair open in fuel control circuit.
14. Repair short to voltage in fuel control circuit.
15. Replace IC module.
16. Check terminal contact at fuel control circuit terminal at PCM harness connector. Repair as necessary. If terminal contact is okay, go to next step.
17. Replace PCM. Program replacement PCM using required equipment.

DTC P0325 - KNOCK SENSOR MODULE CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

The PCM stores a calibrated time that it considers to be a valid spark knock duration. If PCM sees a knock event that is longer in duration that the acceptable stored time, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition off. Remove Knock Sensor (KS) module from PCM. Install a known-good KS module. Using FAILURE REC. snapshot data from scan tool, duplicate conditions when DTC originally set. Using scan tool, select DTC INFO then FAIL THIS IGN. function. If DTC P0325 resets, go to next step. If DTC P0325 does not reset, go to step 4).
3. Replace PCM. Program replacement PCM using required equipment.
4. Replace KS module.

DTC P0326 - KNOCK SENSOR CIRCUIT EXCESSIVE SPARK RETARD

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

DTC will set if knock system is otherwise functioning normally, but is detecting excessive knock. This may be due to a noisy engine producing excessive mechanical vibrations from piston slap, valve closures, etc. Excessive knock could also be produced by very low octane fuel.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Start engine. Observe if engine is producing excessive mechanical noise. If excessive noise is observed, go to next step. If excessive noise is not observed, go to step 4).
3. Locate and repair source of noise.
4. Use higher octane fuel. If higher octane fuel is not available, go to next step. If higher octane fuel is used, go to step 6).
5. Using scan tool, select MORE then select SERV. SPARK under MISC. TEST function. Activate SERV. SPARK (this can lower base timing from 10° to 6°BTDC). Retard base timing at 2°BTDC increments as needed. SERV. SPARK will stay at set reading until changed with scan tool or when power to PCM is disconnected.
6. Fill fuel tank with premium fuel. Drive vehicle for about 15 minutes, allowing PCM to adjust to the premium fuel.

DTC P0327 - KNOCK SENSOR LOW VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

During engine operation, Knock Sensor (KS) will detect background noise on its circuits. PCM monitors this noise and compares the amount of noise it monitors to the amount of noise it expects to see. DTC will set of knock sensor background noise is less than an expected learned value at a given RPM and TP sensor range for a given period of time.

Conditions for setting DTC

1. Ignition voltage at least 10 volts.
2. Coolant temperature at least 104°F (40°C).
3. Throttle position at least 4.8 degrees.
4. Engine speed at least 3000 RPM.
5. Battery voltage at least 11 volts.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Disconnect knock sensor/starter solenoid harness connector (on right side of engine compartment). Set DVOM to 400 mV AC scale. Check frequency (Hertz) at KS connector terminal. Tap on engine block with a non-metallic object. If frequency fluctuates while tapping block, go to step 5). If frequency does not fluctuate, go to next step.
3. Remove intake manifold. Disconnect knock sensor harness connector. Using DVOM, check frequency (Hertz) directly at knock sensor. Tap on engine block with a non-metallic object. If frequency fluctuates while tapping on block, go to next step. If frequency does not fluctuate, go to step 9).
4. Repair open or short to ground in circuit between knock sensor and knock sensor/starter solenoid harness connector.
5. Reconnect knock sensor/starter solenoid harness connector. Using scan tool, select STORE INFO. and save data stored when DTC was set. Store fluid life value as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Using DVOM, check frequency at PCM harness connector knock signal circuit, while tapping on engine block. If frequency fluctuates while tapping on block, go to step 7). If frequency does not fluctuate, go to next step.
6. Repair open or short to ground in circuit between PCM connector C2 and knock sensor/starter solenoid harness connector terminal.
7. Reconnect PCM connector. Using scan tool, select FAILURE REC. and note conditions under which the DTC set. Operate vehicle with engine temperature at about 104°F (40°C), TP sensor at 4.8 degrees, engine speed at 3000 RPM and ensure battery voltage is at least 11 volts. If DTC resets, go to next step. If DTC does not reset, fault is not present. See DIAGNOSTIC AIDS.
8. Check terminal contact at PCM connector C2 knock sensor signal circuit. Repair as necessary. If terminal contact is okay, go to step 11).
9. Check terminal contact at knock sensor. Repair as necessary. If terminal contact is okay, go to next step.
10. Replace knock sensor.
11. Replace PCM. Program replacement PCM using required equipment.

Check for an intermittent open or short in knock sensor circuit.

DTC P0340 - IGNITION CONTROL (IC) MODULE CAM REFERENCE CIRCUIT NO FREQUENCY

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for camshaft pulses not received when 4X reference pulses are being received. This indicates that a camshaft sensor circuit failure and DTC will set.

Conditions for setting DTC

1. DTC P0322 not set.
2. 4X reference pulses being received.
3. Engine speed 1600 RPM or less.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if «DTC P1376»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p1376-ignition-ground-circuit) is also present. If DTC P1376 is present, diagnose DTC first. If DTC P1376 is not present, go to next step.
3. Turn ignition off. Disconnect IC module connector C2. Using DVOM, check resistance between camshaft position sensor harness connector terminals. If resistance is 800-2100 ohms, go to next step. If resistance is not as specified, go to step 6).
4. Individually check resistance to ground at both IC module harness connector terminals. If resistance at either terminals is less than 100 ohms, go to step 12). If not, go to next step.
5. Disconnect IC module connector C3. Set DVOM to "peak min/max", 4-volt scale. Connect DVOM across camshaft position sensor harness connector terminals. Crank engine. If DVOM reads greater than .2 volt, go to step 9). If not, go to step 17).
6. If resistance is less than 800 ohms, go to next step. If resistance is not less than 800 ohms, go to step 8).
7. Disconnect camshaft position sensor connector. Check resistance between sensor harness connector terminals. If resistance is greater than 10,000 ohms, go to step 17). If not, go to step 13).
8. Disconnect camshaft position sensor. Individually check continuity in sensor low and high signal circuits. If continuity is present on both circuits, go to step 17). If continuity is not present on both or either circuits, go to step 14).
9. Reconnect IC module harness connector C2. Disconnect IC module harness connector C4. Using scan tool, store fluid life index as indicated. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Using DVOM, check resistance between ground camshaft position sensor signal circuit at PCM harness connector terminal. If resistance is less than 10,000 ohms, go to step 16). If not, go to next step.
10. Check resistance between camshaft position sensor signal circuit at PCM harness connector terminal. If resistance is 5 ohms or less, go to next step. If not, go to step 15).
11. Reconnect IC module connectors C3 and C4. Using DVOM, set DVOM to "peak min/max" 4-volt DC scale and push HERTZ button. Connect DVOM between IC module harness connector terminal "B" (cam signal circuit) and ground. Crank engine. If frequency reading is greater than .4 Hz, go to step 21). If frequency reading is not greater than .4 Hz, go to step 19).
12. Repair short to ground in camshaft position sensor circuits between sensor and IC module harness connector.
13. Repair short between camshaft position sensor circuits.
14. Repair open or high resistance in camshaft position sensor circuits.
15. Repair open in cam signal circuit to PCM.
16. Repair short to ground in cam signal circuit to PCM.
17. Check terminal contact at camshaft position sensor terminal. Repair as necessary. If terminal contacts are okay, go to next step.
18. Replace camshaft position sensor.
19. Check terminal contact at IC module. Repair as necessary. If terminal contact is okay, go to next step.
20. Replace IC module.
21. Check terminal contact to cam signal circuit at PCM connector. Repair as necessary. If terminal contact is okay, go to next step.
22. Replace PCM. Program replacement PCM using required equipment.

DTC P0371 - IGNITION CONTROL (IC) MODULE 24X REFERENCE CIRCUIT TOO MANY PULSES

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for 49 or greater 24X reference pulses between CAM pulses. If pulses vary between too few or too many of the allowed range between CAM events, DTC will set.

Conditions for setting DTC

1. DTC P1376 not set.
2. At least one CAM pulse received in the last .25 second.
3. Engine speed 496-3500 RPM.
4. Number of CAM edges since key on is 7 or greater.
5. Eight 24X pulses seen between cam pulses.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Check for possible cause of Electromagnetic Interference (EMI), such as spark plug wires routed too close to IC module, high power transmitters operating within vicinity or the use of a battery charger. If possible source of EMI is found, remove source. If EMI interference is not noticed, go to next step.
3. Clear DTC(s) and retest. If DTC P0371 resets, go to next step. If DTC P0371 does not reset, fault is not present.
4. Check terminal contact of 24X spark reference circuit at IC module and PCM harness connector. Repair as necessary. If terminal contact is okay, go to next step.
5. Replace IC module.

DTC P0372 - IGNITION CONTROL (IC) MODULE 24X REFERENCE CIRCUIT MISSING PULSES

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for less than 48 pulses between CAM pulses. If pulses vary between too few or too many of the allowed range between CAM events, DTC will set.

Conditions for setting DTC

1. DTC P1376 not set.
2. At least one CAM pulse received in the last .25 second.
3. Engine speed 496-3500 RPM.
4. Number of CAM edges since key on is 7 or greater.
5. Eight 24X pulses seen between cam pulses.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, verify if DTC P1323 is also present. If DTC P1323 is present, diagnose this DTC first. If DTC P1323 is not present, go to next step.
3. Turn ignition off. Disconnect IC module harness connector C4. Using 6-Pin IC Module Diagnostic Jumpers, jumper the following IC module connector C4 terminals to the following module terminals: C4 Terminal "A" To Module Pin "A" C4 Terminal "B" To Module Pin "B" C4 Terminal "C" To Module Pin "C" C4 Terminal "D" To Module Pin "D" C4 Terminal "E" To Module Pin "E" C4 Terminal "F" To Module Pin "F" Set DVOM to 400 mV AC scale and push Hz button. Connect DVOM between terminal "A" jumper and ground. Start engine and check frequency. If frequency is 200 Hz or greater, go to next step. If not, go to step 5).
4. Check terminal contact for 24X spark reference circuit at PCM connector C2. Check 24X reference circuit between PCM and IC module harness connectors. Repair as necessary. If terminal contact and circuit are okay, go to step 10).
5. Turn ignition on. Disconnect all jumpers. Turn ignition on. Using DVOM, check voltage between ground and cam low circuit terminal at IC module connector C4. If voltage is greater than 4.2 volts, go to next step. If not, go to step 8).
6. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Reconnect IC module harness connector C4. Turn ignition on. Using DVOM, check voltage between ground and 24X spark reference circuit at PCM harness connector C2. Voltage reading should be 4.2 volts. If voltage is greater than 4.2 volts, go to step 4). If not, go to next step.
7. Repair short to ground in 24X spark reference circuit.
8. Check terminal contact of cam signal circuit at IC module harness connector C4. Repair as necessary. If circuit is okay, go to next step.
9. Replace IC module.
10. Replace PCM. Program replacement PCM using required equipment.

DTC P0401 - EGR SYSTEM MALFUNCTION

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

EGR operation will cause variations in MAP sensor because when EGR valve opens, exhaust gas is drawn through it with intake manifold vacuum. When all test enable conditions are met, the test begins with PCM cycling the EGR from off to on and on to off, and recording the change in MAP. The PCM then converts MAP change to percentage and calculates the MAP error, or the difference between the actual percentage MAP change and the percentage MAP change that the PCM expected to see. The PCM performs this test several times to gain an average. If at least 8 tests have occurred, PCM compares its current average MAP error to the failure limit.

For EGR "off" test, if the current average MAP error is 6 kPa or greater, DTC is set. If error is less than the limit, EGR operation is returned to normal software control.

For the EGR "on" test, if at least 8 tests have occurred, the PCM compares its current average MAP error to the failure limit. If current average MAP error is 7 kPa or greater, DTC is set. If error is less than the limit, EGR operation is returned to normal software control.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. If fuel trim DTC(s) P0170, P0171, P0172, P0173, P0174 or P0175 are present, diagnose affected DTC(s) first. If these DTC(s) are not present, go to next step.
3. Ignition on, with engine off. Check MAP sensor parameter on scan tool. If value is greater than 75 kPa (95 kPa at sea level), go to next step. If not, go to step 9).
4. Unplug MAP sensor vacuum hose. Connect a hand-held vacuum pump to MAP sensor. Apply 20 in. Hg to sensor. Each one in. of vacuum should result in a 3-4 kPa drop in MAP sensor reading. Change should be smooth. If a skip or jump occurs during application of vacuum, go to step 9). If change in reading is smooth, go to next step.
5. With 20 in. Hg applied to sensor, if MAP reading is 34 kPa or less, go to next step. If not, go to step 9).
6. Remove vacuum source from MAP sensor. If MAP sensor parameter returns to original reading, go to next step. If not, go to step 9).
7. Reconnect MAP sensor vacuum hose. Start and idle engine. While monitoring MAP sensor value, command EGR from 0-70 percent in 10 percent increments. MAP sensor value should increase by about 4 kPa for each 10 percent increment. If MAP value does not increase accordingly and engine does not stall, go to next step. If MAP value increases accordingly or engine stalls, check EGR system for intermittent restrictions, blockages and/or leaks. If no fault is found, problem is intermittent.
8. Check EGR valve and all engine passages for restrictions and/or blockages. Repair as necessary. If no repairs are required, go to step 10).
9. Replace MAP sensor.
10. Replace EGR valve and verify if problem is no longer present.

DTC P0404 - EGR SYSTEM

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for malfunction in the circuitry and hardware of the linear EGR valve. The ability of the PCM to control the EGR valve is checked with this test. When PCM commands the EGR valve to desired position and changes that position less than a calibrated amount, this test then checks the EGR pintle position error (difference between desired and actual pintle position). If pintle position error is too great, this DTC will set.

Conditions for setting DTC

1. Ignition voltage 12 volts or less.
2. EGR pintle position error is greater than 75 counts.
3. Ignition voltage greater than 12 volts.
4. EGR pintle position error is greater than 25 counts.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check EGR pintle position. If scan tool displays 0.18-2.06 volts, go to next step. If not, go to step 8).
3. Using scan tool, select OUTPUT TESTS for EGR. Command EGR to 0 percent. Check EGR pintle position display. If scan tool displays one volt or less, go to next step. If not, go to step 20).
4. Command EGR to 50 percent. Check EGR pintle position display. If scan tool displays 2-3 volts, go to next step. If not, go to step 25).
5. Command EGR to 100 percent. Check EGR pintle position display. If scan tool displays 4 volts, go to next step. If not, go to step 22).
6. Select FREEZE FRAME or FAILURE REC. Check EGR pintle position when DTC was set. If voltage reading is .18 volt or greater, go to next step. If not, go to step 21).
7. If voltage reading is 5 volts or greater, go to step 24). If not, go to step 21).
8. If voltage reading is .18 volts or less, go to next step. If not, go to step 16).
9. Exit OUTPUT TESTS. Using scan tool, check EGR pintle position. Disconnect EGR valve harness connector. Jumper EGR harness connector terminals "C" and "D". If voltage reading is .18 volts or less, go to next step. If not, go to step 15).
10. Using DVOM, check voltage between ground and jumper wire. If voltage reading is less than 4.5 volts, go to next step. If not, go to step 26).
11. Remove jumper wire. Check voltage between ground and EGR harness connector terminal "D". If voltage reading less than 4.5 volts. Go to next step. If not, go to step 27).
12. Using scan tool, store fluid life data. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector. Disconnect TP sensor harness connector. Check resistance between ground and EGR harness connector terminal "D". If resistance is greater than 10,000 ohms, go to next step. If not, go to step 28).
13. Check resistance between PCM harness connector terminal No. 62 and EGR harness connector terminal "D". If resistance is less than 5 ohms, go to next step. If not, go to step 29).
14. Check terminal contact at PCM harness connector C1 terminal No. 62. Repair as necessary. If terminal contact is okay, go to step 35).
15. Check terminal contact at EGR harness connector. Repair as necessary. If terminal contact is okay, go to step 34).
16. Exit OUTPUT TESTS. Using scan tool, check EGR pintle position. Disconnect EGR harness connector. If voltage reading is less than 2.06 volts, go to next step. If not, go to step 30).
17. Disconnect TP sensor and ECT sensor harness connectors. Using DVOM, check voltage between ground and EGR harness connector terminal "B". If voltage reading is 0.1 volt or less, go to next step. If not, go to step 31).
18. Check voltage between ground and EGR harness connector terminal "D". If voltage reading is 5.5 volts or less, go to next step. If not, go to step 32).
19. Store fluid life data. Turn ignition off. Wait 30 seconds, then disconnect PCM harness connector C1. Check resistance between PCM harness connector terminal No. 7 and EGR harness connector terminal "B". If resistance is less than 5 ohms, go to step 15). If not, go to step 33).
20. Check for poor terminal contact at EGR harness connector and PCM harness connector C1. Check for high resistance in EGR pintle position ground, sticky EGR valve. Check for intermittent short to ground in EGR position feedback circuit, the 5-volt reference circuit and the EGR pintle position ground circuit. Repair as necessary. If circuits are okay, fault is not present.
21. Check terminal contact at PCM and EGR harness connectors. Check for sticky EGR valve or debris in EGR system, causing EGR valve to stick. Repair as necessary. If repairs were not required, fault is not present.
22. Check for terminal contact at PCM and EGR harness connectors. Check for high resistance in EGR position feedback circuit 5-volt reference circuit. Check for a sticky EGR valve. Repair as necessary. If repairs were not required, fault is not present.
23. Check for intermittent opens or shorts to ground in 5-volt reference circuit and EGR position feedback circuit. Repair as necessary. If repairs were not required, fault is not present.
24. Check for intermittent open in EGR pintle position ground circuit. Check for intermittent short to voltage in EGR position feedback circuit, EGR pintle position ground circuit or the 5-volt reference circuit. The reference circuit short may be located on any of the PCM 5-volt reference circuit (i.e. TP sensor 5-volt reference). Repair as necessary. If repairs were not required, fault is not present.
25. Check for intermittent open or short in the ignition feed circuit and EGR valve control circuit. Check for a sticky EGR valve. Repair as necessary. If repairs were not required, fault is not present.
26. Repair open in EGR position feedback circuit.
27. Repair short to ground in EGR position feedback circuit.
28. Repair short to ground in 5-volt reference circuit. Short may be located on any of the PCM 5-volt reference circuits (i.e. TP sensor 5-volt reference).
29. Repair open in 5-volt reference circuit.
30. Repair short to voltage in EGR position feedback circuit.
31. Repair short to voltage in EGR pintle position ground circuit.
32. Repair short to voltage in 5-volt reference circuit.
33. Repair open in EGR pintle position ground circuit.
34. Replace EGR valve.
35. Replace PCM. Program replacement PCM using required equipment.

DTC P0405 - EGR VALVE SENSOR CIRCUIT VOLTAGE OUT OF RANGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for a malfunction in circuitry and hardware of linear EGR valve. The pintle position sensor voltage is monitored for an out of range condition when EGR valve is closed.

Conditions of setting DTC

1. Ignition voltage is greater than 11 volts.
2. Closed EGR valve pintle position sensor voltage is .32 volt or less, or 3.69 volts or greater.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check EGR pintle position. If voltage reading is 0.18-2.06 volts, go to next step. If not, go to step 8).
3. Select OUTPUT TESTS for EGR. Command EGR valve to 0 percent. Check EGR pintle position display. If voltage reading is 1.0 volt or less, go to next step. If not, go to step 20).
4. Command EGR to 50%. Check EGR pintle position display. If voltage reading is 2-3 volts, go to next step. If not, go to step 25).
5. Command EGR to 100 percent. Check EGR pintle position display. If voltage reading is 4 volts or greater, go to next step. If not, go to step 22).
6. Using scan tool, select FREEZE FRAME or FAILURE REC. Check EGR pintle position when DTC was set. If voltage reading is 0.18 volt or greater, go to next step. If not, go to step 23).
7. If voltage reading is 5 volts or greater, go to step 24). If not, go to step 21).
8. If voltage reading is 0.18 volt or less, go to next step. If not, go to step 16).
9. Exit OUTPUT TESTS. Using scan tool, check EGR pintle position. Disconnect EGR valve harness connector. Jumper EGR harness connector terminals "C" and "D". If voltage reading is 0.18 volt or less, go to next step. If not, go to step 15).
10. Using DVOM, check voltage between ground and jumper wire. If voltage reading is 4.5 volts or less, go to next step. If not, go to step 26).
11. Remove jumper wire. Check voltage between ground and EGR harness connector terminal "D". If voltage reading is less than 4.5 volts, go to next step. If not, go to step 27).
12. Using scan tool, store fluid life data. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector. Disconnect TP sensor harness connector. Check resistance between ground and EGR harness connector terminal "D". If resistance is greater than 10,000 ohms, go to next step. If not, go to step 28).
13. Check resistance between PCM harness connector terminal No. 62 and EGR harness connector terminal "D". If resistance is less than 5 ohms, go to next step. If not, go to step 29).
14. Check terminal contact at PCM connector C1 terminal No. 62. Repair as necessary. If terminal contact is okay, go to step 35).
15. Check terminal contact at EGR harness connector. Repair as necessary. If terminal contact is okay, go to step 34).
16. Exit OUTPUT TESTS. Using scan tool, check EGR pintle position. Disconnect EGR harness connector. If voltage reading is less than 2.06 volts, go to next step. If not, go to step 30).
17. Disconnect TP sensor and ECT sensor harness connectors. Using DVOM, check voltage between ground and EGR harness connector terminal "B". If voltage reading is 0.1 volt or less, go to next step. If not, go to step 31).
18. Check voltage between ground and EGR harness connector terminal "D". If voltage reading is 5.5 volts or less, go to next step. If not, go to step 32).
19. Store fluid life data. Turn ignition off. Wait 30 seconds, then disconnect PCM harness connector C1. Check resistance between PCM harness connector terminal No. 7 and EGR harness connector terminal "B". If resistance is less than 5 ohms, go to step 15). If not, go to step 33).
20. Check for poor terminal contact at EGR harness connector and PCM harness connector C1. Check for high resistance in EGR pintle position ground, sticky EGR valve. Check for intermittent short to ground in EGR position feedback circuit, the 5-volt reference circuit and the EGR pintle position ground circuit. Repair as necessary. If circuits are okay, fault is not present.
21. Check terminal contact at PCM and EGR harness connectors. Check for sticky EGR valve or debris in EGR system, causing EGR valve to stick. Repair as necessary. If repairs were not required, fault is not present.
22. Check for terminal contact at PCM and EGR harness connectors. Check for high resistance in EGR position feedback circuit 5-volt reference circuit. Check for a sticky EGR valve. Repair as necessary. If repairs were not required, fault is not present.
23. Check for intermittent opens or shorts to ground in 5-volt reference circuit and EGR position feedback circuit. Repair as necessary. If repairs were not required, fault is not present.
24. Check for intermittent open in EGR pintle position ground circuit. Check for intermittent short to voltage in EGR position feedback circuit, EGR pintle position ground circuit or the 5-volt reference circuit. The reference circuit short may be located on any of the PCM 5-volt reference circuit (i.e. TP sensor 5-volt reference). Repair as necessary. If repairs were not required, fault is not present.
25. Check for intermittent open or short in the ignition feed circuit and EGR valve control circuit. Check for a sticky EGR valve. Repair as necessary. If repairs were not required, fault is not present.
26. Repair open in EGR position feedback circuit.
27. Repair short to ground in EGR position feedback circuit.
28. Repair short to ground in 5-volt reference circuit. Short may be located on any of the PCM 5-volt reference circuits (i.e. TP sensor 5-volt reference).
29. Repair open in 5-volt reference circuit.
30. Repair short to voltage in EGR position feedback circuit.
31. Repair short to voltage in EGR pintle position ground circuit.
32. Repair short to voltage in 5-volt reference circuit.
33. Repair open in EGR pintle position ground circuit.
34. Replace EGR valve.
35. Replace PCM. Program replacement PCM using required equipment.

DTC P0420 - TWC SYSTEM LOW EFFICIENCY

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test monitors catalytic converter efficiency. This runs only once per ignition cycle and only after the converter has warmed up to operating temperature. Converter efficiency is calculated using data collected from pre- and post-converter oxygen sensors during steady driving conditions. The pre-converter oxygen sensor signal should fluctuate like those of the front and rear oxygen sensor. The post-converter oxygen sensor signal should fluctuate less than the pre-converter oxygen sensor.

The catalytic converter efficiency test is performed in 2 stages. The first stage calculates post-converter oxygen sensor deviations (difference from the average value), compares these deviations to the maximum allowable deviation (based on air flow), and records a failure if those deviations are excessive. The second stage is only run if the first stage fails or DTC P0420 is currently set. The second stage averages the difference between the deviations calculated in the first stage and the maximum allowable deviations. If the second stage average is too high, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
3. Check exhaust system for leaks, damage, loose or missing hardware. Repair as necessary. After repairs, go to step 5). If exhaust system is okay, go to next step.
4. Ensure original 3-way catalytic converter is installed. Check catalytic converter for damage or tampering. Ensure oxygen sensors are properly installed and wiring and connections are okay. Repair or replace components as necessary. After repairs, go to next step. If components are okay, go to step 6).
5. Using scan tool, select DTC INFO then DTC STATUS under DTC mode. Operate vehicle under which DTC was set. Observe scan tool display of DTC STATUS, looking for DTC to run or fail. If this DTC failed, go to next step. If this DTC did not fail, system is okay.
6. Replace catalytic converter.

Fuel with high sulfur content can cause a marginal converter to look bad. Check fuel quality.

DTC P0441 - EVAP SYSTEM NO FLOW DURING PURGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test determines if the Evaporative Emission (EVAP) control solenoid is open when the PCM is commanding it to open. PCM does this by monitoring EVAP vacuum switch which is a normally closed switch. Switch is located in vacuum line between EVAP canister and EVAP solenoid. When the switch opens, vacuum from the engine draws evaporative emissions from EVAP canister into throttle body.

The state of the EVAP switch is monitored by the PCM to determine if EVAP solenoid is open and passing vacuum. The PCM accomplishes this by monitoring the amount of time the EVAP switch is continuously open or closed during purge. The the test conditions are met, PCM starts a timer, which will be reset when the switch transitions from open to closed or vice versa. If switch remains closed for 9 seconds continuously, DTC will set. If switch remains open for 2 seconds continuously, test is passed.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Check if «DTC P1645»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p1645-evap-purge-solenoid) is also present. If DTC P1645 is present, diagnose DTC first. If DTC P1645 is not present, go to next step.
3. Start engine. Using scan tool, select EVAP VACUUM SW. Command EVAP solenoid on (100 percent). If scan tool reads PURGING, go to next step. If scan tool does not read PURGING, go to step 12).
4. Disconnect EVAP vacuum switch connector. If scan tool reads PURGING, go to next step. If not, go to step 12).
5. Reconnect EVAP switch connector. Disconnect EVAP vacuum switch vacuum hose (solenoid side) and install a "T" fitting between vacuum hose to solenoid. Connect a vacuum gauge to fitting. Start engine. Check vacuum with engine at idle and EVAP solenoid commanded on (100 percent). If vacuum reading is 4 in. Hg or greater, go to next step. If not, go to step 7).
6. Replace EVAP vacuum switch.
7. Disconnect EVAP control solenoid vacuum hose (intake manifold side). Connect vacuum gauge to hose and check vacuum with engine running. If vacuum reading is 4 in. Hg or greater, go to next step. If not, go to step 9).
8. Reconnect vacuum hose to EVAP control solenoid. Disconnect vacuum hose on other side (switch side) of EVAP control solenoid. Connect vacuum gauge on solenoid port. Check vacuum reading with engine running and EVAP control solenoid commanded on (100 percent). If vacuum reading is 4 in. Hg or greater, go to step 11). If not, go to step 10).
9. Repair blocked or leaking vacuum hose between intake manifold and EVAP control solenoid.
10. Replace EVAP control solenoid.
11. Check for vacuum leak in system between EVAP control solenoid and vapor canister, including switch. Repair as necessary. If vacuum leak is not present, go to step 13).
12. Repair short to ground in EVAP vacuum switch input circuit.
13. Replace vapor canister.

Never apply voltage to EVAP vacuum switch. Voltage supplied by PCM is of low current design. Switch damage could result if jumpered to voltage.

DTC P0506 - IAC SYSTEM RPM LOW

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test determines if idle control system is maintaining the proper idle speed. The IAC system controls idle speed by allowing a certain amount of air to bypass the throttle body (throttle plate closed during idle) through the IAC valve. The PCM controlled IAC motor moves a pintle in and out of IAC valve, varying the amount of air entering the intake manifold. DTC will set when engine idle speed is less than 80 RPM or greater than the desired idle speed for 15 seconds.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
3. Start and idle engine. Turn off all accessories. Using scan tool, select MISC TESTS and select IAC SYSTEM. Command engine speed up to 1500 RPM, down to 500 RPM, then back to 1500 RPM while monitoring ENGINE SPEED display. If ENGINE SPEED display remains within 50 RPM of desired value for each RPM command, fault is not present. If engine speed is not within 50 RPM of desired value, go to next step.
4. Disconnect IAC valve. Install IAC Noid Light (J 37027). Start engine. Command engine speed up to 1500 RPM, down to 500 RPM, then back to 1500 RPM while monitoring noid light. If noid light cycles Red and Green (never off), go to step 6). If noid light does not cycle, go to next step.
5. Check all IAC circuits for open, short to ground or short to voltage. Repair as necessary. If circuits are okay, go to step 9).
6. Check throttle body for objects blocking IAC passage or throttle bore, excessive deposits in IAC passage, pintle, throttle bore or throttle plate. Check for restriction or vacuum leaks in air intake system. Check adjustment screw for tampering. Repair as necessary. If no problems are found, go to next step.
7. Check for poor terminal contact at IAC harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
8. Replace IAC valve.
9. Check IAC terminal contacts at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
10. Replace PCM. Program replacement PCM using required equipment.

DTC P0507 - IAC SYSTEM RPM HIGH

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test determines if idle control system is maintaining the proper idle speed. The IAC system controls idle speed by allowing a certain amount of air to by-pass the throttle body (throttle plate closed during idle) through the IAC valve. The PCM controlled IAC motor moves a pintle in and out of IAC valve, varying the amount of air entering the intake manifold. DTC will set when engine idle speed is greater than the desired idle speed for 15 seconds.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
3. Start and idle engine. Turn off all accessories. Using scan tool, select MISC TESTS and select IAC SYSTEM. Command engine speed up to 1500 RPM, down to 500 RPM, then back to 1500 RPM while monitoring ENGINE SPEED display. If ENGINE SPEED display remains within 50 RPM of desired value for each RPM command, fault is not present. If engine speed is not within 50 RPM of desired value, go to next step.
4. Disconnect IAC valve. Install IAC Noid Light (J 37027). Start engine. Command engine speed up to 1500 RPM, down to 500 RPM, then back to 1500 RPM while monitoring noid light. If noid light cycles Red and Green (never off), go to step 6). If noid light does not cycle, go to next step.
5. Check all IAC circuits for open, short to ground or short to voltage. Repair as necessary. If circuits are okay, go to step 9).
6. Check throttle body for objects blocking IAC passage or throttle bore, excessive deposits in IAC passage, pintle, throttle bore or throttle plate. Check for restriction or vacuum leaks in air intake system. Check adjustment screw for tampering. Repair as necessary. If no problems are found, go to next step.
7. Check for poor terminal contact at IAC harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
8. Replace IAC valve.
9. Check IAC terminal contacts at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
10. Replace PCM. Program replacement PCM using required equipment.

DTC P0550 - POWER STEERING PRESSURE SWITCH CIRCUIT VOLTAGE LOW

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

Power Steering Pressure (PSP) switch is normally closed switch, which opens when power steering pressure exceeds 450-650 psi. The PSP switch closes again when pressure drops to less than 100-450 psi. This test monitors the PSP switch. When load is placed on power steering, such as full lock position, the switch opens. When driving at greater than 45 MPH (no load condition), the switch is closed. DTC sets when vehicle speed is greater than 45 MPH and the PSP switch signal is open.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, select PSP SWITCH. With engine running, turn steering wheel from straight ahead to full left lock position and back to straight ahead position. If scan tool displays NORMAL to HI PRESS and back to NORMAL, fault is not present. See DIAGNOSTIC AIDS. If scan tool does not display NORMAL to HI PRESS and back to NORMAL, go to next step.
3. Turn engine off. Turn ignition on, with engine off. If scan tool display remains on HI PRESS, go to next step. If scan tool display does not remain on HI PRESS, go to step 8).
4. Disconnect PSP switch. Using DVOM, check voltage between ground and PSP switch harness connector terminal "B". If voltage is 10 volts or greater, go to next step. If not, go to step 10).
5. Using jumper wire, jumper PSP switch harness connector terminals. If scan tool displays HI PRESS, go to next step. If scan tool does not display HI PRESS, go to step 11).
6. Store fluid life value as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. With PSP switch harness connector terminals jumpered, turn ignition on. Check voltage between ground and PSP switch input circuit at PCM harness connector terminal. If voltage reading is 10 volts or greater, go to next step. If not, go to step 12).
7. Check PSP switch input harness connector terminal at PCM connector C1. Repair as necessary. If harness connector terminals are okay, go to step 17).
8. Turn ignition on, with engine off. Disconnect PSP switch harness connector. If scan tool displays NORMAL, go to next step. If scan tool does not display NORMAL, go to step 11).
9. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Turn ignition on. Check voltage between ground and PSP switch input circuit at PCM harness connector C1. If voltage reading is .5 volt or less, go to step 7). If not, go to step 13).
10. Check fuse. If fuse is blown, go to step 14). If fuse is not blown, go to step 15).
11. Check terminal contacts at PSP switch. Repair as necessary. If terminal contacts are okay, go to step 16).
12. Repair open or short in PSP switch input circuit between PCM harness connector and PSP switch harness connector.
13. Repair short to voltage in PSP switch input circuit between PCM harness connector and PSP switch harness connector.
14. Replace faulty fuse and check/repair short in ignition circuit to PSP switch.
15. Repair open in ignition circuit to PSP switch.
16. Replace PSP switch.
17. Replace PCM. Program replacement PCM using required equipment.

Check for intermittent contact at PSP switch or stretching of harness causing an intermittent open.

DTC P0560 - SYSTEM VOLTAGE LOW

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM monitors system voltage on ignition feed circuit to PCM harness connector C1. DTC will set if this voltage drops to less than 10 volts, with engine running at greater than 500 RPM. If ignition voltage is zero volts (open circuit), engine will not operate since PCM does not have the ignition feed voltage to operate.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Start engine. Using scan tool, note IGNITION 1 voltage reading. Compare this voltage to voltage displayed by the Instrument Panel Cluster (IPC) message center. Scan tool and IPC voltage difference should be within .5 volt. If difference is greater than .5 volt, go to next step. If scan tool and IPC voltage is within .5 volt, diagnose charging system. See DIAGNOSTIC AIDS.
3. Using DVOM, check voltage between ground and PCM fuse. Scan tool and DVOM voltage difference should be within .5 volt. If voltage difference is greater than .5 volt, go to next step. If voltage is within .5 volt or the same, diagnose charging system.
4. Check for high resistance in ignition feed circuit to PCM. Repair circuit as necessary. If circuit is okay, go to next step.
5. Check terminal contact PCM harness connectors C1 and C2. Repair as necessary. If terminal contacts are okay, go to next step.
6. Replace PCM. Program replacement PCM using required equipment.

Normal running system voltage is about 15 volts. A loose or faulty connection at generator "L" terminal may cause DTC to set intermittently.

DTC P0563 - SYSTEM VOLTAGE HIGH

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM monitors system voltage on ignition feed circuit to PCM harness connector C1. DTC will set if this voltage is greater than 16 volts for 6 seconds.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Start engine. Using scan tool, note IGNITION 1 voltage reading. Compare this voltage to voltage displayed by the Instrument Panel Cluster (IPC) message center. If difference is greater than .5 volt, go to next step. If scan tool and IPC voltage is within .5 volt or the same, diagnose charging system. See DIAGNOSTIC AIDS.
3. Using DVOM, check voltage to ground on PCM fuse. If difference is greater than .5 volt, go to next step. If scan tool and DVOM voltage is the same or within .5 volt, diagnose charging system.
4. Check for high resistance in ignition feed circuit to PCM. Repair circuit as necessary. If circuit is okay, go to next step.
5. Check terminal contact PCM harness connectors C1 and C2. Repair as necessary. If terminal contacts are okay, go to next step.
6. Replace PCM. Program replacement PCM using required equipment.

Normal running system voltage is about 15 volts. A loose or faulty connection at generator "L" terminal may cause DTC to set intermittently.

The PCM EPROM contains data essential in running engine and transaxle. This test check the integrity of the data. The EPROM data is divided into 2 halves or sides in the EPROM. The integrity of the data is checked by adding up the data in all locations of the EPROM. This is called the checksum. If checksum does not equal to what it should, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Replace PCM. Program replacement PCM using required equipment.

DTC is designed not to allow a service/replacement PCM to be installed without first flashing software into it.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Flash PCM with correct software. Check if DTC resets. If DTC resets, go to next step.
3. Replace PCM. Program replacement PCM using required equipment.

The PCM has a memory area where it stores certain data it needs to save when the ignition is turned off. This area is called Keep Alive Memory. This test monitors PCM's keep alive memory for a loss or unintended change of data. If such a condition occurs, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check for other DTC(s) set. If other DTC(s) are set, diagnose affected DTC(s). If other DTC(s) are not present, see DIAGNOSTIC AIDS.

If battery has been disconnected for any reason, DTC P0603 will set. The PCM keeps a running check on the memory and if it changes, memory will reset. An intermittent loss of power or ground to PCM will cause a reset.

PCM has 2 internal processors, the ECM and the TCM. They are connected together and share data on an interconnect called SPI. The ECM sends sensor data to TCM. This sensor data is checked and if the difference in readings between the 2 processors is too great, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Replace PCM. Program replacement PCM using required equipment.

DTC P1106 - MAP SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

MAP sensor changes resistance based upon manifold vacuum. PCM provides a 5-volt reference and ground signal and monitors a signal circuit. MAP sensor signal varies between ground and 5 volts as manifold vacuum varies. As MAP decreases, voltage decreases (low engine load, high vacuum). As MAP increases, voltage increases (high engine load, low vacuum). PCM uses MAP sensor value as an indicator of engine load. DTC will set when PCM detects a MAP sensor value that is too high.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, verify if DTC P0106 or P0108 is also present. If these DTC(s) are present, diagnose affected DTC(s) first. If these DTC(s) are not present, go to next step.
3. Turn ignition off. Disconnect harness connector to MAP sensor. Check harness connector terminals. Repair as necessary. If terminals are okay, go to next step.
4. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Check MAP sensor terminals at PCM harness connector. Repair as necessary. If terminals are okay, go to step 5).
5. Disconnect MAP sensor connector. Check all sensor terminals. Repair as necessary. If terminals are okay, go to next step.
6. Check MAP sensor 5-volt reference and signal circuits for intermittent short to voltage. Also, check for open MAP sensor ground circuit. Repair as necessary. If circuits are okay, fault is not present. Diagnose using «DTC P0106»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0106-map-system-performance) test.

DTC P1107 - MAP SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

MAP sensor changes resistance based upon manifold vacuum. PCM provides a 5-volt reference and ground signal. MAP sensor signal varies between one and 5 volts as manifold vacuum varies. As MAP decreases, voltage decreases (low engine load, high vacuum). As MAP increases, voltage increases (high engine load, low vacuum). PCM uses MAP sensor value as an indicator of engine load. DTC will set when PCM detects a MAP sensor value that is too low.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, verify if DTC P0106 or P0107 is also present. If these DTC(s) are present, diagnose affected DTC(s) first. If these DTC(s) are not present, go to next step.
3. Turn ignition off. Disconnect harness connector to MAP sensor. Check harness connector terminals. Repair as necessary. If terminals are okay, go to next step.
4. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Check MAP sensor terminals at PCM harness connector. Repair as necessary. If terminals are okay, go to step 5).
5. Disconnect MAP sensor connector. Check all sensor terminals. Repair as necessary. If terminals are okay, go to next step.
6. Check MAP sensor 5-volt reference and signal circuits for intermittent short to voltage. Also, check for open MAP sensor ground circuit. Repair as necessary. If circuits are okay, fault is not present. Diagnose using «DTC P0106»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0106-map-system-performance) test.

DTC P1108 - BARO-TO-MAP SENSOR CIRCUIT COMPARISON TOO HIGH

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

MAP sensor changes resistance based upon manifold vacuum. PCM provides a 5-volt reference and ground signal. MAP sensor signal varies between ground and 5 volts as manifold vacuum varies. As MAP decreases, voltage decreases (low engine load, high vacuum). As MAP increases, voltage increases (high engine load, low vacuum). PCM uses MAP sensor value as an indicator of engine load.

This test monitors the MAP signal by comparing the reading to calculated BARO. If the values of the MAP signal and the calculated BARO are too close together at idle, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Start and idle engine. Using scan tool, select ENGINE 1 and note MAP and BARO displays. Subtract MAP value from BARO value. If difference between BARO and MAP value is 11 kPa or less, go to next step. If difference is greater than 11 kPa, fault is not present. Diagnose using «DTC P0106»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0106-map-system-performance) tests.
3. Connect vacuum gauge at MAP sensor port. With engine at idle, if vacuum is 14 in. Hg or greater, go to next step. If vacuum is not greater than 14 in. Hg, go to step 14).
4. Turn engine off. Disconnect MAP sensor harness connector. Turn ignition to LOCK position. Note MAP display on scan tool. If MAP sensor display reads 16 kPa or less, go to next step. If MAP sensor display does not read 16 kPa or less, go to step 7).
5. Check voltage between ground and MAP sensor ground circuit at MAP sensor harness connector terminal. If voltage is greater than .5 volt, go to step 12). If voltage is not greater than .5 volt, go to next step.
6. Store fluid life index as indicated on scan tool. Turn ignition to LOCK position, then disconnect PCM harness connector C1 and MAP sensor harness connector terminals. Using DVOM, check resistance of MAP sensor ground circuit between PCM harness connector and MAP harness connector terminals. If resistance is 5 ohms or less, go to step 11). If resistance is not 5 ohms or less, go to step 9).
7. Store fluid life index as indicated on scan tool. Turn ignition to LOCK position and wait 30 seconds, then disconnect PCM harness connector C1 and MAP sensor harness connector terminals. Using DVOM, check voltage between chassis ground and MAP sensor ground circuit at MAP sensor harness connector terminal "B". If voltage reading is .5 volt or less, go to step 10). If voltage reading is not .5 volt or less, go to next step).
8. Repair short to voltage in MAP sensor signal circuit.
9. Repair open in MAP sensor ground circuit.
10. Check terminal contact to MAP sensor at PCM harness connector C1. Repair as necessary. If terminal contact is okay, go to step 15).
11. Repair terminal contact MAP sensor harness connector. Repair as necessary. If terminal contact is okay, go to step 13).
12. Repair short to voltage in MAP sensor 5-volt reference circuit.
13. Replace MAP sensor.
14. Check and repair causes of intake manifold vacuum leaks or low engine vacuum.
15. Replace PCM. Program replacement PCM using required equipment.

DTC P1111 - IAT SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

IAT sensor is a thermistor that varies resistance based on temperature. Low temperature will result in high resistance and high monitored signal voltage. If IAT reading is -30°F (-35°C) or lower when coolant temperature is hotter than IAT reading, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P0111 or «DTC P0113»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0113-iat-sensor-circuit) is also present. If either DTC is present, diagnose affected DTC first. If these DTC(s) are not present, go to next step.
3. Store fluid life index as indicated on scan tool. Turn ignition on and wait 30 seconds, then disconnect PCM harness connectors C1 and C2. Check terminals to IAT sensor at PCM harness connectors C1 and C2. Repair as necessary. If terminal contacts are okay, go to next step.
4. Disconnect and check IAT sensor harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
5. Check IAT sensor signal and ground circuits for open or short to voltage between IAT sensor harness connector and PCM harness connector. Repair as necessary. If circuits are okay, fault is not present. See DIAGNOSTIC AIDS.

If fault is not present, check PCM grounds. If a faulty sensor is suspected, check sensor resistance. See IAT TEMPERATURE-TO-RESISTANCE VALUES .

DTC P1112 - IAT SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

IAT sensor is a thermistor that varies resistance based on temperature. High temperature will result in low signal voltage. If IAT reading is 304°F (151°C) or greater when coolant temperature is less than 230°F (110°C), DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P0111 or P0112 is also present. If either DTC is present, diagnose affected DTC first. If these DTC(s) are not present, go to next step.
3. Store fluid life index as indicated on scan tool. Turn ignition on and wait 30 seconds, then disconnect PCM harness connectors C1 and C2. Check terminals to IAT sensor at PCM harness connectors C1 and C2. Repair as necessary. If terminal contacts are okay, go to next step.
4. Disconnect and check IAT sensor harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
5. Check IAT sensor signal circuit for short to ground. Repair as necessary. If circuit is okay, fault is not present. See DIAGNOSTIC AIDS.

If fault is not present, check PCM grounds. If a faulty sensor is suspected, check sensor resistance.

DTC P1114 - ECT SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

ECT sensor is a thermistor that varies resistance based on temperature. High temperature will result in low signal voltage. If ECT reading is 304°F (151°C) or greater, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if «DTC P0116»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0116-ect-sensor-circuit) or P0117 is also present. If either DTC is present, diagnose affected DTC first. If these DTC(s) are not present, go to next step.
3. Store fluid life index as indicated on scan tool. Turn ignition on and wait 30 seconds, then disconnect PCM harness connectors C1 and C2. Check terminals to ECT sensor at PCM harness connectors C1 and C2. Repair as necessary. If terminal contacts are okay, go to next step.
4. Disconnect and check ECT sensor harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
5. Check ECT sensor signal circuit for short to ground. Repair as necessary. If circuit is okay, fault is not present. See DIAGNOSTIC AIDS.

If fault is not present, check PCM grounds. If a faulty sensor is suspected, check for skewed ECT sensor.

DTC P1115 - ECT SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

ECT sensor is a thermistor or a variable resistor, that varies resistance based on temperature. High temperature will result in low signal voltage. If ECT reading is less than -36°F (-38°C) when IAT reading is greater than 23°F (-5°C) or vehicle has driving long enough for coolant temperature to increase to greater than -36°F (-38°C), DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if «DTC P0116»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0116-ect-sensor-circuit) or P0118 is also present. If either DTC is present, diagnose affected DTC first. If these DTC(s) are not present, go to next step.
3. Store fluid life index as indicated on scan tool. Turn ignition on and wait 30 seconds, then disconnect PCM harness connectors C1 and C2. Check terminals to ECT sensor at PCM harness connectors C1 and C2. Repair as necessary. If terminal contacts are okay, go to next step.
4. Disconnect and check ECT sensor harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
5. Check ECT sensor signal and ground circuits for open or short to voltage. Repair as necessary. If circuit is okay, fault is not present. See DIAGNOSTIC AIDS.

If fault is not present, check PCM grounds. Check for skewed ECT sensor. See ECT TEMPERATURE-TO-RESISTANCE VALUES table.

ECT TEMPERATURE-TO-RESISTANCE VALUES

DTC P1121 - TP SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

TP sensor is a potentiometer. At low throttle angle, the TP sensor signal voltage is low. The PCM uses TP sensor information to determine idle, Wide Open Throttle (WOT), deceleration enleanment and acceleration enrichment. DTC will when PCM detects a TP sensor signal that is 5 volts or greater, which is not possible under normal operation.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if «DTC P0120»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l) or P0123 is also present. If either DTC is present, diagnose affected DTC first. If these DTC(s) are not present, go to next step.
3. Store fluid life index as indicated on scan tool. Turn ignition on and wait 30 seconds, then disconnect PCM harness connector C1. Check terminals to TP sensor at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
4. Disconnect and check TP sensor harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
5. Check for open in TP sensor ground circuit. Check for short to voltage in TP sensor 5-volt reference and signal circuits. Repair as necessary. If circuits are okay, fault is not present. See DIAGNOSTIC AIDS.

If fault is not present, check PCM grounds.

DTC P1122 - TP SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

TP sensor is a potentiometer. At low throttle angle, the TP sensor signal voltage is low. The PCM uses TP sensor information to determine idle, Wide Open Throttle (WOT), deceleration enleanment and acceleration enrichment. DTC will when PCM detects a TP sensor signal that is 0.1 volt or less.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if «DTC P0120»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l) or P0123 is also present. If either DTC is present, diagnose affected DTC first. If these DTC(s) are not present, go to next step.
3. Store fluid life index as indicated on scan tool. Turn ignition on and wait 30 seconds, then disconnect PCM harness connector C1. Check terminals to TP sensor at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
4. Disconnect and check TP sensor harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
5. Check for open or short to ground in TP sensor 5-volt reference and signal circuits. Repair as necessary. If circuits are okay, fault is not present. See DIAGNOSTIC AIDS.

If fault is not present, check PCM grounds.

DTC P1133 - HO2S INSUFFICIENT SWITCHING BANK 1, SENSOR 1 (REAR)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a 5-volt reference signal to the oxygen sensor. When oxygen sensor is cold, sensor signal voltage will be about 5 volts and PCM will keep the system in "open loop" operation. When oxygen sensor is warm, sensor will swing from rich to lean rapidly (one swing every 2 seconds), if PCM is in good control of air/fuel mixture. If oxygen is slow to respond to changes in exhaust oxygen content, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. If you were sent here from another DTC, go to step 4). If not, go to next step.
3. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
4. Start engine. Using scan tool, select ENGINE 1 and observe ECT display. Operate engine until temperature reaches 185°F (85°C). Note ENGINE SPEED and BNK 1 SEN 1 display. Operate engine at 1200-2000 RPM for about 2 minutes. After 2 minutes check if rear oxygen sensor voltage rapidly swings from less than .3 volt to greater than .6 volt. If oxygen sensor voltage is swinging as specified, go to next step. If oxygen sensor voltage is not swinging as specified, go to step 6).
5. With engine running at 1200-2000 RPM, note scan tool display LOOP STATUS. If display indicates CLOSED, fault is not present. See DIAGNOSTIC AIDS. If display does not indicate CLOSED, go to step 9).
6. If rear oxygen sensor voltage remains between .3-.6 volt longer that it swings out of this range, go to step 9). If oxygen sensor voltage swings, go to next step.
7. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
8. Check terminal contact at rear oxygen sensor connector. Repair as necessary. If harness connector is okay, go to next step.
9. Replace rear oxygen sensor. Check for possible sensor contamination, i.e. leaded fuel, incorrect gasket seal or over rich operation. If failure is caused by over rich condition, check fuel injection system. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article.

If fault is not present, check PCM grounds. Never solder oxygen sensor wires.

DTC P1134 - HO2S TRANSITION TIME RATIO BANK 1, SENSOR 1 (REAR)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test is used in conjunction with the rear oxygen sensor slow response diagnostic test (DTC P0133). The ratio of the response times that was calculated are compared to calibrated limits. If the number of both lean-to-rich transitions (switches) and rich-to-lean transitions were both zero, then ratio will be set to zero. Otherwise, the ratio is calculated based on which average response time was greater.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
3. Start engine. Using scan tool, select ENGINE 1 and observe ECT display. Operate engine until temperature reaches 185°F (85°C). Note ENGINE SPEED and BNK 1 SEN 1 display. Operate engine at 1200-2000 RPM for about 2 minutes. After 2 minutes check if rear oxygen sensor voltage rapidly swings from less than .3 volt to greater than .6 volt. If oxygen sensor voltage is swinging as specified, go to next step. If oxygen sensor voltage is not swinging as specified, go to step 5).
4. With engine running at 1200-2000 RPM, note scan tool display LOOP STATUS. If display indicates CLOSED, fault is not present. See DIAGNOSTIC AIDS. If display does not indicate CLOSED, go to step 8).
5. If rear oxygen sensor voltage remains between .3-.6 volt longer than it swings out of this range, go to step 8). If oxygen sensor voltage does not remain within range, go to next step.
6. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
7. Check terminal contact at rear oxygen sensor connector. Repair as necessary. If harness connector is okay, go to next step.
8. Replace rear oxygen sensor. Check for possible sensor contamination, i.e. leaded fuel, incorrect gasket seal or over rich operation. If failure is caused by over rich condition, check fuel injection system. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article.

If fault is not present, check PCM grounds. Never solder oxygen sensor wires.

DTC P1139 - HO2S INSUFFICIENT SWITCHING BANK 1, SENSOR 2 (PRE-CONVERTER)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a 5-volt reference signal to the oxygen sensor. When oxygen sensor is cold, sensor signal voltage will be about 5 volts and PCM will keep the system in "open loop" operation. When oxygen sensor is warm, sensor will swing from rich to lean rapidly (one swing every 2 seconds), if PCM is in good control of air/fuel mixture. If oxygen sensor is slow to respond to changes in exhaust oxygen content, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. If you were sent here from another DTC, go to step 4). If not, go to next step.
3. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
4. Start engine. Using scan tool, select ENGINE 1 and observe ECT display. Operate engine until temperature reaches 185°F (85°C). Note ENGINE SPEED and BNK 1 SEN 2 display. Operate engine at 1200-2000 RPM for about 2 minutes. After 2 minutes check if rear oxygen sensor voltage rapidly swings from less than .3 volt to greater than .6 volt. If oxygen sensor voltage is swinging as specified, go to next step. If oxygen sensor voltage is not swinging as specified, go to step 6).
5. With engine running at 1200-2000 RPM, note scan tool display LOOP STATUS. If display indicates CLOSED, fault is not present. See DIAGNOSTIC AIDS. If display does not indicate CLOSED, go to step 9).
6. If rear oxygen sensor voltage remains between .3-.6 volt longer than it swings out of this range, go to step 9). If not, go to next step.
7. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
8. Check terminal contact at pre-converter oxygen sensor connector. Repair as necessary. If harness connector is okay, go to next step.
9. Replace pre-converter oxygen sensor. Check for possible sensor contamination, i.e. leaded fuel, incorrect gasket seal or over rich operation. If failure is caused by over rich condition, check fuel injection system. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article.

If fault is not present, check PCM grounds. Never solder oxygen sensor wires.

DTC P1140 - HO2S TRANSITION TIME RATIO BANK 1, SENSOR 2 (PRE-CONVERTER)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test is used in conjunction with the pre-converter oxygen sensor slow response diagnostic test (DTC P0139). The ratio of the response times that was calculated are compared to calibrated limits. If the number of both lean-to-rich transitions (switches) and rich-to-lean transitions were both zero, then the ratio will be set to zero. Other wise, the ratio is calculated based on which average response time was greater.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Start engine. Using scan tool, select ENGINE 1 and observe ECT display. Operate engine until temperature reaches 185°F (85°C). Note ENGINE SPEED and BNK 1 SEN 2 display. Operate engine at 1200-2000 RPM for about 2 minutes. After 2 minutes check if rear oxygen sensor voltage rapidly swings from less than .3 volt to greater than .6 volt. If oxygen sensor voltage is swinging as specified, fault is not present. See DIAGNOSTIC AIDS. If oxygen sensor voltage is not swinging as specified, go to next step.
3. If pre-converter oxygen sensor voltage remains between .3-.6 volt longer that it swings out of this range, go to step 6). If not, go to next step.
4. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
5. Check terminal contact at pre-converter oxygen sensor connector. Repair as necessary. If harness connector is okay, go to next step.
6. Replace pre-converter oxygen sensor. Check for possible sensor contamination, i.e. leaded fuel, incorrect gasket seal or over rich operation. If failure is caused by over rich condition, check fuel injection system. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article.

If fault is not present, check PCM grounds. Never solder oxygen sensor wires.

DTC P1153 - HO2S INSUFFICIENT SWITCHING BANK 2, SENSOR 1 (PRE-CONVERTER)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM provides a 5-volt reference signal to the oxygen sensor. When oxygen sensor is cold, sensor signal voltage will be about 5 volts and PCM will keep the system in "open loop" operation. When oxygen sensor is warm, 392°F (200°C), sensor will swing from rich to lean rapidly (one swing every 2 seconds), if PCM is in good control of air/fuel mixture. If oxygen is slow to respond to changes in exhaust oxygen content, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. If you were sent here from another DTC, go to step 4). If not, go to next step.
3. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
4. Start engine. Using scan tool, select ENGINE 1 and observe ECT display. Operate engine until temperature reaches 185°F (85°C). Note ENGINE SPEED and BNK 2 SEN 1 display. Operate engine at 1200-2000 RPM for about 2 minutes. After 2 minutes check if pre-converter oxygen sensor voltage rapidly swings from less than .3 volt to greater than .6 volt. If oxygen sensor voltage is swinging as specified, go to next step. If oxygen sensor voltage is not swinging as specified, go to step 6).
5. With engine running at 1200-2000 RPM, note scan tool display LOOP STATUS. If display indicates CLOSED, fault is not present. See DIAGNOSTIC AIDS. If display does not indicate CLOSED, go to step 9).
6. If pre-converter oxygen sensor voltage remains between .3-.6 volt longer that it swings out of this range, go to step 9). If not, go to next step.
7. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
8. Check terminal contact at pre-converter oxygen sensor connector. Repair as necessary. If harness connector is okay, go to next step.
9. Replace pre-converter oxygen sensor. Check for possible sensor contamination, i.e. leaded fuel, incorrect gasket seal or over rich operation. If failure is caused by over rich condition, check fuel injection system. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article.

If fault is not present, check PCM grounds. Never solder oxygen sensor wires.

DTC P1154 - HO2S TRANSITION TIME RATIO BANK 2, SENSOR 1 (FRONT)

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test is used in conjunction with the front oxygen sensor slow response diagnostic test ( DTC P0153 ). The ratio of the response times that was calculated are compared to calibrated limits. If the number of both lean-to-rich transitions (switches) and rich-to-lean transitions were both zero, then ratio will be set to zero. Other wise, the ratio is calculated based on which average response time was greater.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
3. Start engine. Using scan tool, select ENGINE 1 and observe ECT display. Operate engine until temperature reaches 185°F (85°C). Note ENGINE SPEED and BNK 2 SEN 1 display. Operate engine at 1200-2000 RPM for about 2 minutes. After 2 minutes, check if front oxygen sensor voltage rapidly swings from less than .3 volt to greater than .6 volt. If oxygen sensor voltage is swinging as specified, go to next step. If oxygen sensor voltage is not swinging as specified, go to step 5).
4. With engine at 1200-2000 RPM, note scan tool LOOP STATUS display. If scan tool display reads CLOSED, fault is not present. See DIAGNOSTIC AIDS. If scan tool display does not read CLOSED, go to step 8).
5. If front oxygen sensor voltage remains between .3-.6 volt longer that it swings out of this range, go to step 8). If not, go to next step.
6. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
7. Check terminal contact at front oxygen sensor connector. Repair as necessary. If harness connector is okay, go to next step.
8. Replace front oxygen sensor. Check for possible sensor contamination, i.e. leaded fuel, incorrect gasket seal or over rich operation. If failure is caused by an over rich condition, check fuel injection system. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article.

If fault is not present, check PCM grounds. Never solder oxygen sensor wires.

DTC P1258 - ENGINE OVER-TEMPERATURE PROTECTION

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM has the ability to disable 4 injectors during an engine over temperature (overheating) condition. Engine is considered over temperature whenever ECT reaches 268°F (131°C). This protection mode allows the PCM to alternate between groups of cylinders, thereby reducing coolant temperature. This is accomplished by disabling the fuel injectors. This DTC is set to show that an overheating condition was or is observed by the PCM and that the protection mode has been engaged.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P0108 or P1114 is set. If any of these DTC(s) are present, diagnose affected DTC(s). If DTC(s) are not present, diagnose cooling system.

DTC P1320 - IGNITION CONTROL (IC) MODULE 4X REFERENCE CIRCUIT INTERMITTENT NO PULSE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

IC module creates a 4X signal and a 24X signal that is used by the PCM for ignition and fuel control. If PCM does not receive 4X reference pulses from the IC module for greater than .4 second while engine is running, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC(s) P0322, P1323 or P1375 is also present. If any of the DTC(s) are present, diagnose affected DTC(s) first. If DTC(s) are not present, go to next step.
3. Disconnect IC module harness connector C3. Turn ignition on. Using DVOM, check voltage between ground and ignition feed circuit at IC module harness connector C3. If voltage is 10 volts or greater, go to next step. If not, go to step 10).
4. Turn ignition off. Reconnect IC module harness connector C3. Disconnect IC module harness connector C4. Store fluid life index as indicated on scan tool. Disconnect PCM harness connector C2. Using DVOM, check resistance between ground and fuel control circuit at PCM harness connector terminal. If resistance is greater than 10,000 ohms go to next step. If not, go to step 11).
5. Check resistance of fuel control circuit between IC module harness connector and PCM harness connector terminal. If resistance is 5 ohms or less, go to next step. If not, step 12).
6. Turn ignition on. Check voltage between ground and fuel control circuit at IC harness connector C2. If voltage is less than .5 volt go to next step. If not, go to step 13).
7. Reconnect IC module harness connector C4. Check voltage between ground and fuel control circuit at PCM harness connector C2. If voltage is greater than 4.2 volts, go to next step. If not, go to step 14).
8. Turn ignition off. Disconnect IC module harness connector C2. Using 6-Pin IC Module Diagnostic Jumpers, jumper the following IC module connector C4 terminals to the following module terminals: C4 Terminal "A" To Module Pin "A" C4 Terminal "B" To Module Pin "B" C4 Terminal "C" To Module Pin "C" C4 Terminal "D" To Module Pin "D" C4 Terminal "E" To Module Pin "E" C4 Terminal "F" To Module Pin "F" Set DVOM to 400 mV AC scale and push Hz button. Connect DVOM between terminal "C" jumper and ground. Start engine and check frequency. If frequency is less than 30 Hz, go to step 10). If frequency is not less than 30 Hz, go to next step.
9. Remove all jumper wire connections. Reconnect IC module connector C4. Clear DTC. Start and idle engine. Using scan tool, select DTC INFO then FAIL THIS IGN modes. If DTC P1320 resets, go to step 16). If DTC does not reset, fault is not present. See DIAGNOSTIC AIDS.
10. Check for no voltage to IC module caused by a faulty fuse due to short in ignition feed circuit, open in ignition feed circuit or shorted IC module. Repair as necessary.
11. Repair short to ground in fuel control circuit to IC module.
12. Repair open in fuel control circuit to IC module.
13. Repair short to voltage in fuel control circuit to IC module.
14. Check terminal contact at IC module harness connector C4. Repair as necessary. If terminal contact is okay, go to next step.
15. Replace IC module.
16. Check fuel control circuit terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
17. Replace PCM. Program replacement PCM using required equipment.

DTC may set due to a false start condition in which cranking speed exceeds 568 RPM with engine not starting. If no fault is present, check for intermittent open or short in IC module fuel control circuit, ignition feed circuit or ground circuit. Also, check for EMI interference on IC module fuel control circuit.

DTC P1323 - IGNITION CONTROL (IC) MODULE 24X REFERENCE CIRCUIT LOW FREQUENCY

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

IC module creates a 4X signal and a 24X signal that is used by the PCM for ignition and fuel control. In this test, PCM checks for 4X reference pulses being received without 24X reference pulses. When engine is running and PCM is receiving 4X pulses without 24X reference pulses and the 24X reference signal line is low for 4 seconds, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P1376 is also present. If DTC P1376 is present, diagnose this DTC first. If DTC is not present, go to next step.
3. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect IC module harness connector C4 and PCM harness connector C2. Using DVOM, check resistance between ground and 24X reference circuit at PCM harness connector C2. If resistance is greater than 10,000 ohms, go to next step. If not, go to step 8).
4. Check resistance of 24X reference signal circuit between PCM and IC harness connector terminals. If resistance is 5 ohms or less, go to next step. If not, go to step 9).
5. Reconnect IC module harness connector C4. Turn ignition on. Check voltage between ground and 24X reference signal circuit at PCM harness connector C2. If voltage is greater than 4.2 volts, go to next step. If not, go to step 10).
6. Turn ignition off. Disconnect IC module harness connector C2. Using 6-Pin IC module diagnostic jumpers, jumper the following IC module connector C4 terminals to the following module terminals: C4 Terminal "A" To Module Pin "A" C4 Terminal "B" To Module Pin "B" C4 Terminal "C" To Module Pin "C" C4 Terminal "D" To Module Pin "D" C4 Terminal "E" To Module Pin "E" C4 Terminal "F" To Module Pin "F" Set DVOM to 400 mV AC scale and push Hz button. Connect DVOM between terminal "A" jumper and ground. Start engine and check frequency. If frequency is less than 340 Hz, go to step 10). If frequency is not less than 340 Hz, go to next step.
7. Remove all jumper wire connections. Reconnect IC module connector C4. Clear DTC. Start and idle engine. Using scan tool, select DTC INFO then FAIL THIS IGN modes. If DTC P1323 resets, go to step 12). If DTC does not reset, fault is not present. See DIAGNOSTIC AIDS.
8. Check for short to ground in 24X reference signal circuit.
9. Repair open in 24X reference signal circuit.
10. Check terminal contact at IC module harness connector C4. Repair as necessary. If terminal contact is okay, go to next step.
11. Replace IC module.
12. Check 24X reference signal circuit terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
13. Replace PCM. Program replacement PCM using required equipment.

DTC may set due to a false start condition in which cranking speed exceeds 568 RPM with engine not starting. If no fault is present, check for intermittent open or short in IC module fuel control circuit, ignition feed circuit or ground circuit. Also, check for EMI interference on IC module 24X reference signal circuit.

DTC P1350 - IGNITION CONTROL (IC) SYSTEM

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

Under normal operation, until engine RPM is high enough for the PCM to control spark, PCM will open the by-pass circuit to the IC module, the IC module will then ground the IC module circuit. This mode is called the module mode, because the IC module is controlling the spark at his point. Once engine speed is high enough (about 65 RPM), the 4X reference pulses are received and if no PCM faults are detected, PCM will close the by-pass line and in response the IC module will unground the IC circuit, allowing PCM to control spark. This mode is called the control mode.

This test is used to check for faults in both the by-pass and the IC circuit. To check both circuits, this diagnostic runs 2 tests. One during crank and one while engine is running. If IC control pulses are detected by the PCM on the IC line while in module mode (cranking) or if no ignition control pulses are detected by the PCM while in ignition control mode (running), DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P0322, P0372, P1323, P1371 or P1376 is also present. If any of these DTC(s) are present, diagnose affected DTC(s) first. If DTC(s) are not present, go to next step.
3. Using scan tool, select DTC and select FAILURE REC and note ENGINE SPEED snapshot display for DTC P1350. If engine speed display reads less than 500 RPM, go to next step. If engine speed display reads greater than 500 RPM, go to step 9).
4. Turn ignition off. Disconnect IC module harness connector C4. Using 6-Pin IC module diagnostic jumpers, jumper the following IC module connector C4 terminals to the following module terminals: C4 Terminal "A" To Module Pin "A" C4 Terminal "B" To Module Pin "B" C4 Terminal "C" To Module Pin "C" C4 Terminal "D" To Module Pin "D" C4 Terminal "E" To Module Pin "E" C4 Terminal "F" To Module Pin "F" Turn ignition on. Using DVOM, check voltage between terminal "D" jumper and ground. If voltage is less than .4 volt, go to next step. If not, go to step 7).
5. Remove injector fuses from underhood fuse/relay block. Crank engine and check voltage on terminal "E" jumper. If voltage reading is 1.3 volts or greater, go to next step. If not, fault is not present. See DIAGNOSTIC AIDS.
6. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2 and disconnect all jumpers from IC module connector. Check resistance of IC signal circuit between PCM harness connector and IC module harness connector terminals. If resistance is 5 ohms or less, go to step 25). If not, go to step 19).
7. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage reading. If voltage is .4 volt or less, go to next step. If not, go to step 27).
8. Turn ignition off. Disconnect all jumper wires, but leave IC module harness connector C4 disconnected. Turn ignition on. Check voltage between ground and by-pass circuit at PCM harness connector terminal. If voltage reading is .4 volt or greater, go to step 20). If not, go to step 25).
9. Turn ignition off. Disconnect IC module harness connector C4. Using 6-Pin IC Module Diagnostic Jumpers, jumper the following IC module connector C4 terminals to the following module terminals: C4 Terminal "A" To Module Pin "A" C4 Terminal "B" To Module Pin "B" C4 Terminal "C" To Module Pin "C" C4 Terminal "D" To Module Pin "D" C4 Terminal "E" To Module Pin "E" C4 Terminal "F" To Module Pin "F" Start engine. Using DVOM, check voltage between terminal "D" jumper and ground. If voltage reading is 4.1 volts or greater, go to next step. If not, go to step 17).
10. Turn ignition off. Remove all jumper connectors, leaving IC module harness connector disconnected. Disconnect PCM harness connector C2. Using DVOM, check by-pass circuit between IC module connector and PCM connector terminals. If resistance is 5 ohms or less, go to next step. If not, go to step 21).
11. Reconnect PCM harness connector C2 and IC module harness connector jumpers. Set DVOM to 4-volt scale and push the Hz button. Start engine. Connect DVOM between jumper "E" terminal and ground. Frequency reading should be 30-100 Hertz. If frequency is as specified, fault is not present. See DIAGNOSTIC AIDS. If frequency is as specified, go to next step.
12. Set DVOM to DC voltage scale.With engine running check voltage at jumper "E" terminal and ground. If voltage reading is 4 volts or less, go to next step. If not, go to step 15).
13. Turn ignition off. Disconnect jumpers from IC module harness connector C4. Set DVOM to PEAK MIN/MAX setting. Turn ignition on. Check voltage between ground and ignition control circuit at IC module harness connector C4 terminal. If voltage reading is 3.7 volts or less, go to next step. If voltage reading is greater than 3.7 volts, go to step 25).
14. Turn ignition off. Disconnect PCM harness connector C2. Check resistance between ground and ignition control circuit at IC module harness connector terminal. If resistance is 10,000 ohms or less, go to step 22). If not, go to step 27).
15. Turn ignition off. Disconnect jumpers from IC module harness connect C4. Turn ignition on. Check voltage between ground and ignition control circuit at IC module harness connector C4 terminal. If voltage reading is 1.3 volts or less, go to step 25). If not, go to next step.
16. Turn ignition off. Disconnect PCM harness connector C2. Turn ignition on. Check voltage between ground and ignition control circuit at IC module harness connector C4. If voltage is greater than .5 volt, go to step 23). If not, go to step 27).
17. Turn ignition off. Disconnect jumpers from IC module harness connector. Disconnect PCM harness connector C2. Check resistance between ground and by-pass signal circuit at PCM harness connector terminal. If resistance is less than 5000 ohms, go to step 24). If not, go to next step.
18. Reconnect PCM harness connector C2. Reconnect all jumper wires at IC module harness connector C4. Turn ignition on. Clear all DTC(s). Turn ignition off. Disconnect EGR harness connector. Jumper EGR harness connector terminal "D" (5-volt reference) to IC module harness connector C4 jumper "D" terminal. Start engine. Check if DTC P1350 resets. If DTC resets, go to step 27). If DTC does not reset, go to step 25).
19. Repair open in ignition control circuit.
20. Repair short to voltage in by-pass signal circuit.
21. Repair open in by-pass signal circuit.
22. Repair short to ground in ignition control circuit.
23. Repair short to voltage in ignition control circuit.
24. Repair short to ground in by-pass signal circuit.
25. Check terminal contact at IC module harness connector C4. Repair as necessary. If terminal is okay, go to next step.
26. Replace IC module.
27. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
28. Replace PCM. Program replacement PCM using required equipment.

If fault is not present, check terminal contact at IC module and PCM harness connectors.

DTC P1370 - IGNITION CONTROL (IC) MODULE 4X REFERENCE CIRCUIT TOO MANY PULSES

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for too many 4X reference pulses between cam pulses. PCM checks to see if there are forty eight 24X reference pulses between cam pulses, and if there are, the PCM assumes it is receiving valid cam pulses. Therefore, if PCM see more than eight 4X reference pulses between cam pulses, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Check for possible sources of Electromagnetic Interference (EMI), such as spark wires routed too close to IC module, high power transmitter operating in the vicinity or a battery charger causing EMI. Correct problem, if present. If EMI is not present, go to next step.
3. Clear DTC(s) and retest. If DTC P1370 resets, go to next step. If DTC does not reset, fault is not present.
4. Check fuel control circuit terminal contact IC module connector C4 and PCM harness connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
5. Replace IC module.

DTC P1371 - IGNITION CONTROL (IC) MODULE 4X REFERENCE CIRCUIT TOO FEW PULSES

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for too few 4X reference pulses between cam pulses. PCM checks to see if there are forty eight 24X reference pulses between cam pulses, and if there are, the PCM assumes it is receiving valid cam pulses. Therefore, if PCM see less than eight 4X reference pulses between cam pulses, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC(s) P0322 or P1302 is also present. If DTC(s) are present, diagnose affected DTC(s) first. If DTC(s) are not present, go to next step.
3. Check for possible sources of Electromagnetic Interference (EMI), such as spark wires routed too close to IC module, high power transmitter operating in the vicinity or a battery charger causing EMI. Correct problem, if present. If EMI is not present, go to next step.
4. Clear DTC(s) and retest. If DTC P1371 resets, go to next step. If DTC does not reset, fault is not present. See DIAGNOSTIC AIDS.
5. Check fuel control circuit terminal contact in IC module connector C4 and PCM harness connector C2. Check for possible open or short in fuel control signal circuit. Repair as necessary. If terminal contacts or circuits are okay, go to next step.
6. Replace IC module.

An intermittent short or open to ground in the fuel control circuit to the PCM may set DTC. Check terminals carefully.

DTC P1375 - IGNITION CONTROL (IC) MODULE 24X REFERENCE CIRCUIT HIGH VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for 24X signal at a logic high condition. The fault could be induced by the failure of either crankshaft position "A" or "B" sensor input signal to the IC module. Under such a condition, the IC module would force the 24X signal high. This DTC will also set if the 24X signal is shorted to voltage externally. If either condition is met DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if «DTC P1376»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p1376-ignition-ground-circuit) is also present. If DTC P1376 is present, diagnose DTC first. If DTC P1376 is not present, go to next step.
3. Turn ignition off. Disconnect IC module harness connector C1. Using DVOM, check resistance between IC module harness connector terminals "A" and "B". If resistance is 800-1600 ohms, go to next step. If resistance is not as specified, go to step 11).
4. Check resistance between IC module harness connector terminals "E" and "F". If resistance is 800-1600 ohms, go to next step. If resistance is not as specified, go to step 14).
5. Check resistance between ground and IC module harness connector C1, terminals "A", then "B", then "E" and then "F". If resistance is less than 1000 ohms at each terminal, go to step 17). If not, go to next step.
6. Disconnect IC module harness connector C3. Set DVOM to PEAK MIN/MAX 4-volt scale, one ms sampling rate. Check the MAX DC voltage across IC module harness connector C1 terminals "A" and "B". Crank engine for 10 seconds. If voltage is greater than .25 volt while cranking engine, go to next step. If not, go to step 19).
7. Check MAX DC voltage across IC module harness connector C1 terminals "E" and "F". Crank engine for 10 seconds. If voltage is greater than .25 volt while cranking engine, go to next step. If voltage is not greater than .25 volt, go to step 20).
8. Reconnect IC module harness connectors C1 and C3. Disconnect IC module harness connector C4. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between ground and PCM harness connector C2 terminal No. 5. If voltage is less than .4 volt, go to next step. If voltage is not less than specified, go to step 18).
9. Turn ignition off. Disconnect IC module harness connector C2. Using 6-Pin IC Module Diagnostic Jumpers, jumper the following IC module connector C4 terminals to the following module terminals: C4 Terminal "A" To Module Pin "A" C4 Terminal "B" To Module Pin "B" C4 Terminal "C" To Module Pin "C" C4 Terminal "D" To Module Pin "D" C4 Terminal "E" To Module Pin "E" C4 Terminal "F" To Module Pin "F" Turn ignition on. Set DVOM to 400 mV AC scale and push the Hertz button. Start engine. Connect DVOM between jumper "A" and ground. If frequency reading is greater than zero Hertz, go to next step. If not, go to step 25).
10. Clear all DTC(s). Disconnect terminal "A" jumper only. Start engine. Using scan tool in DTC INFO mode, select FAIL THIS IGN function. If DTC P1323 is present, fault is not present. If DTC P1323 is not present, go to step 27).
11. If resistance in step 3) was lower than the range specified, go to next step. If resistance was higher than the specified range, go to step 27).
12. Disconnect crank sensor "A" harness connector. Check resistance across crank sensor harness connector terminals "A" and "B". If resistance is less than 10,000 ohms, go to step 21). If not, go to step 19).
13. Disconnect crank sensor "A" harness connector. Jumper crank sensor harness connector terminals "A" and "B" together. Check resistance between PCM harness connector C1 terminals "A" and "B". If resistance is greater than 5 ohms, go to step 22). If resistance is less than 5 ohms, go to step 19).
14. If resistance was lower in step 4) than the range that was specified, go to next step. If resistance was greater than the range that was specified, go to step 16).
15. Disconnect crank sensor "B" harness connector. Check resistance across crank sensor harness connector terminals "A" and "B". If resistance is less than 10,000 ohms, go to step 23). If resistance is greater than specified, go to step 20).
16. Disconnect crank sensor "B" harness connector. Jumper crank sensor harness connector terminals "A" and "B" together. Check resistance between IC module connector C1 terminals "E" and "F". If resistance is greater than 5 ohms, go to step 24). If resistance is less than 5 ohms, go to step 20).
17. Repair short to ground in circuit(s) that measured low in step 5).
18. Repair short to voltage in 24X spark reference circuit between IC module and PCM.
19. Replace crank sensor "A".
20. Replace crank sensor "B".
21. Repair crank sensor "A" circuits that are shorted together.
22. Repair open in either crank sensor "A" circuits.
23. Repair crank sensor "B" circuits that are shorted together.
24. Repair open in either crank sensor "B" circuits.
25. Check terminal contact at IC module harness connector C1 terminals 11A, "B", "E" or "F".
26. Replace IC module.
27. Check terminal contact at PCM harness connector terminal "A" (24X spark reference circuit). Repair as necessary. If terminal contact is okay, go to next step.
28. Replace PCM. Program replacement PCM using required equipment.

DTC P1376 - IGNITION GROUND CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM applies 2.5 volts on the reference low circuit to the IC module. Reference low voltage to the PCM represents the voltage difference between reference low and the PCM power ground. This ensures that the PCM and IC module signals all have the same ground reference. If the reference low input voltage goes too high or low, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select FAILURE REC. in DTC mode. Note REF VOLTS LOW display when this DTC set. If voltage reading is 1.4 volts or greater, go to next step. If voltage reading is less than 1.4 volts, go to step 8).
3. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Disconnect IC module harness connector C4. Turn ignition on. Using scan tool, check voltage between ground and reference low circuit at PCM harness connector C2. If voltage is greater than 0.1 volt, go to step 9). If not, go to next step.
4. Check resistance of reference low circuit between IC module harness connector and PCM harness connector terminals. If resistance is 5 ohms or greater, go to step 10). If resistance is less than 5 ohms, go to next step.
5. Turn ignition key on. Check voltage to ground at reference low circuit at IC module harness connector C4. If voltage reading is 0.1 volt or greater, go to next step. If not, fault is not present. See DIAGNOSTIC AIDS.
6. Turn ignition off. Disconnect IC module harness connector C3. Check resistance to ground at IC module harness connector C3 terminal "A" (ground circuit). If resistance is 5 ohms or greater, go to step 11). If not, go to next step.
7. Check terminal contact at IC module and PCM harness connectors. Check PCM and IC module ground connections. Repair as necessary. Reconnect all harness connectors. Clear this DTC. Start engine. If DTC resets, go to step 13). If DTC does not reset, fault is not present.
8. Turn ignition off. Disconnect both PCM harness connectors. Using DVOM, check resistance between ground and PCM ground circuits in PCM terminal. If resistance is greater than 5 ohms in any of the terminals, go to step 12). If not, check PCM grounds.
9. Repair short to voltage in reference low circuit.
10. Repair open in reference low circuit.
11. Repair open in ground circuit to IC module.
12. Repair open in circuits that had high resistance.
13. Replace IC module.

This DTC may set due to an improperly installed PCM, causing PCM not to be electrically isolated from body ground.

DTC P1377 - IGNITION CONTROL (IC) MODULE CAM PULSE TO 4X REFERENCE PULSE COMPARISON

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks to see if there are eight 4X reference pulses between CAM signals. Do not attempt diagnosis or repair unless vehicle is experiencing driveability problems associated with this DTC.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. If any other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
3. If this DTC is set along with a driveability complaint, go to next step. If DTC is not set along with a driveability complaint, fault is not present, see DIAGNOSTIC AIDS.
4. This DTC will set when are too many or too few cam or 4X pulses. Check for Electromagnetic Interference (EMI) being induced in the fuel control circuit, cam signal circuit or camshaft position sensor circuits by improper spark plug wire routing or high power transmitter operating in the vicinity. Correct any causes of EMI. If EMI is not present, go to next step.
5. Check for intermittent short to ground, circuit shorted together or open in fuel control circuit, cam signal circuit or camshaft position sensor circuits. Repair as necessary. If circuits are okay, go to next step.
6. Check terminal contacts at camshaft position sensor terminals. Repair as necessary. If terminal contacts are okay, go to next step.
7. Check terminal contact at camshaft position sensor to IC module. Check terminal contact at fuel control circuit and cam signal circuit to PCM. Repair as necessary. If terminal contacts are okay, fault is not present. See DIAGNOSTIC AIDS.

Since this DTC can set under normal conditions, no diagnosis should be performed unless a driveability complaint is present. This DTC may also set if all 4 camshafts are off by one tooth (10 degrees BTDC), causing a severe driveability problem.

DTC P1380 - EBTCM DTC DETECTED ROUGH ROAD DATA UNUSABLE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This DTC is used to determine when the EBTCM has lost the ability to provide rough road data to the PCM for misfire detection (DTC P0300). When the PCM sees that this condition is present, through the serial data, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, select DTC INFO and note if this DTC has failed this ignition cycle. If DTC failed, diagnose EBTCM system using the BRAKES SYSTEM - ANTI-LOCK article. If DTC did fail this ignition, go to next step.
3. Check EBTCM system for any history ABS/TCS DTC(s) or system problems. If any other DTC(s) or problems are noted, diagnose EBTCM system using the BRAKES SYSTEM - ANTI-LOCK article in the BRAKES section. If not other DTC(s) are present, fault is not present. See DIAGNOSTIC AIDS.

If this DTC is set along DTC P0300, it may represent an invalid misfire due to loss of rough road data. Several ABS system problems could cause a loss of rough road indication from EBTCM. All ABS/TCS system problems and DTC(s) should be corrected first, then duplicate the conditions under which DTC P1380 set and see if problem reoccurs.

DTC P1381 - MISFIRE DETECTED-NO EBTCM/PCM SERIAL DATA

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for the absence of serial data from the EBTCM. This data is needed for misfire diagnosis (DTC P0300), once data is received from the EBTCM. DTC will set if the serial data is lost.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, select DTC INFO and note if this DTC has failed this ignition cycle. If this DTC failed, diagnose EBTCM system. See the BRAKES SYSTEM - ANTI-LOCK article in the BRAKES section. If DTC has not failed this ignition cycle, go to next step.
3. Check EBTCM system for any history ABS/TCS DTC(s) or system problems. If any DTC(s) or problems are noted, diagnose EBTCM using BRAKES SYSTEM - ANTI-LOCK article. If no DTC(s) or problems are noted, fault is not present.

If this DTC is set along with DTC P0300, it may represent an invalid misfire due to a loss of rough road data.

DTC P1404 - EGR VALVE PINTLE STUCK OPEN POSITION

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for malfunction in the circuitry and hardware of the linear EGR valve.This test is used to indicate a stuck open EGR valve. When EGR valve desired position is zero (closed) the current (closed) EGR pintle position is subtracted from the learned low EGR pintle position.

When the open valve condition is indicated, this test waits for EGR to be opened enough so a possible restriction (usually carbon deposits) could possibly clear. When EGR valve desired position returns to zero (closed), this test rechecks the difference between the closed and learned low pintle positions and if significant difference is still there, a timer is incremented. When the time limit has been reached, a failure is indicated and this DTC sets.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check EGR pintle position. If scan tool displays 0.18-2.06 volts, go to next step. If not, go to step 8).
3. Using scan tool, select OUTPUT TESTS for EGR. Command EGR to 0 percent. Check EGR pintle position display. If scan tool displays 1 volt or less, go to next step. If not, go to step 20).
4. Command EGR to 50 percent. Check EGR pintle position display. If scan tool displays 2-3 volts, go to next step. If not, go to step 25).
5. Command EGR to 100 percent. Check EGR pintle position display. If scan tool displays 4 volts, go to next step. If not, go to step 22).
6. Select FREEZE FRAME or FAILURE REC. Check EGR pintle position when DTC was set. If voltage reading is .18 volt or greater, go to next step. If not, go to step 21).
7. If voltage reading is 5 volts or greater, go to step 24). If not, go to step 21).
8. If voltage reading is .18 volt or less, go to next step. If not, go to step 16).
9. Exit OUTPUT TESTS. Using scan tool, check EGR pintle position. Disconnect EGR valve harness connector. Jumper EGR harness connector terminals "C" and "D". If voltage reading is .18 volts or less, go to next step. If not, go to step 15).
10. Using DVOM, check voltage between ground and jumper wire. If voltage reading is less than 4.5 volts, go to next step. If not, go to step 26).
11. Remove jumper wire. Check voltage between ground and EGR harness connector terminal "D". If voltage reading less than 4.5 volts. Go to next step. If not, go to step 27).
12. Using scan tool, store fluid life data. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector. Disconnect TP sensor harness connector. Check resistance between ground and EGR harness connector terminal "D". If resistance is greater than 10,000 ohms, go to next step. If not, go to step 28).
13. Check resistance between PCM harness connector terminal No. 62 and EGR harness connector terminal "D". If resistance is less than 5 ohms, go to next step. If not, go to step 29).
14. Check terminal contact at PCM harness connector C1 terminal No. 62. Repair as necessary. If terminal contact is okay, go to step 35).
15. Check terminal contact at EGR harness connector. Repair as necessary. If terminal contact is okay, go to step 34).
16. Exit OUTPUT TESTS. Using scan tool, check EGR pintle position. Disconnect EGR harness connector. If voltage reading is less than 2.06 volts, go to next step. If not, go to step 30).
17. Disconnect TP sensor and ECT sensor harness connectors. Using DVOM, check voltage between ground and EGR harness connector terminal "B". If voltage reading is 0.1 volt or less, go to next step. If not, go to step 31).
18. Check voltage between ground and EGR harness connector terminal "D". If voltage reading is 5.5 volts or less, go to next step. If not, go to step 32).
19. Store fluid life data. Turn ignition off. Wait 30 seconds, then disconnect PCM harness connector C1. Check resistance between PCM harness connector terminal No. 7 and EGR harness connector terminal "B". If resistance is less than 5 ohms, go to step 15). If not, go to step 33).
20. Check for poor terminal contact at EGR harness connector and PCM harness connector C1. Check for high resistance in EGR pintle position ground, sticky EGR valve. Check for intermittent short to ground in EGR position feedback circuit, the 5-volt reference circuit and the EGR pintle position ground circuit. Repair as necessary. If circuits are okay, fault is not present.
21. Check terminal contact at PCM and EGR harness connectors. Check for sticky EGR valve or debris in EGR system, causing EGR valve to stick. Repair as necessary. If repairs were not required, fault is not present.
22. Check for terminal contact at PCM and EGR harness connectors. Check for high resistance in EGR position feedback circuit 5-volt reference circuit. Check for a sticky EGR valve. Repair as necessary. If repairs were not required, fault is not present.
23. Check for intermittent opens or shorts to ground in 5-volt reference circuit and EGR position feedback circuit. Repair as necessary. If repairs were not required, fault is not present.
24. Check for intermittent open in EGR pintle position ground circuit. Check for intermittent short to voltage in EGR position feedback circuit, EGR pintle position ground circuit or the 5-volt reference circuit. The reference circuit short may be located on any of the PCM 5-volt reference circuit (i.e. TP sensor 5-volt reference). Repair as necessary. If repairs were not required, fault is not present.
25. Check for intermittent open or short in the ignition feed circuit and EGR valve control circuit. Check for a sticky EGR valve. Repair as necessary. If repairs were not required, fault is not present.
26. Repair open in EGR position feedback circuit.
27. Repair short to ground in EGR position feedback circuit.
28. Repair short to ground in 5-volt reference circuit. Short may be located on any of the PCM 5-volt reference circuits (i.e. TP sensor 5-volt reference).
29. Repair open in 5-volt reference circuit.
30. Repair short to voltage in EGR position feedback circuit.
31. Repair short to voltage in EGR pintle position ground circuit.
32. Repair short to voltage in 5-volt reference circuit.
33. Repair open in EGR pintle position ground circuit.
34. Replace EGR valve.
35. Replace PCM. Program replacement PCM using required equipment.

DTC P1441 - EVAP SYSTEM FLOW DURING NON-PURGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test is used to determine if the Evaporative Emission (EVAP) solenoid is open (passing vacuum when the PCM is commanding it closed or if the EVAP switch or circuit is open. The EVAP switch is normally closed switch mounted in the vacuum line between the EVAP canister and the EVAP solenoid. The switch opens when vacuum (7.5 in. Hg) from engine draws the evaporative emissions from the EVAP canister through the EVAP solenoid and into the throttle body.

The PCM monitors the state of the EVAP vacuum switch to determine if EVAP solenoid is open and allowing vacuum to pass. PCM accomplishes this by monitoring the amount of time the EVAP vacuum switch is continuously open or closed with purge off. If switch is open during the test conditions for 9 consecutive seconds, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if «DTC P1645»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p1645-evap-purge-solenoid) is also present. If DTC P1645 is present, diagnose DTC first. If DTC P1645 is not present, go to next step.
3. Turn ignition off. Remove fuel cap for about 10 seconds. Replace fuel cap. Turn ignition on, with engine off. Using scan tool, select ENGINE 2 and note EVAP VACUUM SW display. If scan tool displays PURGING, go to step 9). If scan tool does not display PURGING, go to next step.
4. While observing EVAP VACUUM SWITCH display, start and idle engine. If scan tool displays PURGING, go to next step. If scan tool does not display PURGING, fault is not present. See DIAGNOSTIC AIDS.
5. Note EVAP PURGE SOL display. If scan tool shows duty cycle less than 9.8 percent, go to step 7). If scan tool shows duty cycle at greater than 9.8 percent, go to next step.
6. Select MISC TESTS, then OUTPUT TESTS, then EVAP PURGE. Command EVAP purge solenoid OFF (zero percent). Note EVAP VACUUM SW display. If scan tool displays PURGING, go to next step. If scan tool does not display PURGING, fault is not present. See DIAGNOSTIC AIDS.
7. Check all vacuum lines for proper routing. Repair as necessary. If vacuum line routings are okay, go to next step.
8. Replace EVAP solenoid.
9. Disconnect EVAP vacuum switch. Using jumper wire, jumper EVAP vacuum switch harness connector terminals. If scan tool display shows NO FLOW, go to step 12). If scan tool display does not show NO FLOW, go to next step.
10. Using DVOM, check voltage between ground and EVAP vacuum switch input signal circuit at harness connector terminal. If voltage reading is 10.5 volts or less, go to step 13). If voltage reading is greater than 10.5 volts, go to next step.
11. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Using DVOM, check resistance of EVAP vacuum switch input circuit between PCM harness connector and EVAP vacuum switch harness connector terminals. If resistance is 5 ohms or less, go to step 15). If resistance is greater than 5 ohms, go to step 14).
12. Replace EVAP vacuum switch.
13. Repair open in ground circuit between EVAP vacuum switch and ground.
14. Repair open in EVAP vacuum switch input circuit between switch and PCM harness connector terminal.
15. Check EVAP vacuum switch input circuit terminal contact at PCM harness connector. Repair as necessary. If terminal contact is okay, go to next step.
16. Replace PCM.

Since this test checks for open EVAP vacuum switch while EVAP solenoid is commanded OFF, an EVAP vacuum switch signal problem could set this DTC along with DTC P1442. If an EVAP switch problem is suspected, perform DTC P1442 diagnosis.

If a sticking solenoid is suspected, command EVAP solenoid ON and OFF several times while watching the EVAP switch for the correct display.

DTC P1508 - IAC SYSTEM LOW RPM

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test determines if idle control system is maintaining the proper idle speed. The IAC system controls idle speed by allowing a certain amount of air to by-pass the throttle body (throttle plate closed during idle) through the IAC valve. The PCM controlled IAC motor moves a pintle in and out of IAC valve, varying the amount of air entering the intake manifold.

If engine idle speed is less than the desired idle speed and all test conditions are met, the PCM will cycle the IAC valve and expect to see a change in the MAF sensor reading. If no change occurs DTC P1508 will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Start and idle engine. Turn off all accessories. Using scan tool, select MISC TESTS and select IAC SYSTEM. Command engine speed up to 1500 RPM, down to 500 RPM, then back to 1500 RPM while monitoring ENGINE SPEED display. If ENGINE SPEED display remains within 50 RPM of desired value for each RPM command, fault is not present. If engine speed is not within 50 RPM of desired value, go to next step.
3. Disconnect IAC valve. Install IAC Noid Light (J 37027). Start engine. Command engine speed up to 1500 RPM, down to 500 RPM, then back to 1500 RPM while monitoring noid light. If noid light cycles Red and Green (never off), go to step 5). If noid light does not cycle, go to next step.
4. Check all IAC circuits for open, short to ground or short to voltage. Repair as necessary. If circuits are okay, go to step 8).
5. Check throttle body for objects blocking IAC passage or throttle bore, excessive deposits in IAC passage, pintle, throttle bore or throttle plate. Check for restriction or vacuum leaks in air intake system. Check adjustment screw for tampering. Repair as necessary. If no problems are found, go to next step.
6. Check for poor terminal contact at IAC harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
7. Replace IAC valve.
8. Check IAC terminal contacts at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
9. Replace PCM. Program replacement PCM using required equipment.

DTC P1509 - IAC SYSTEM HIGH RPM

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test determines if idle control system is maintaining the proper idle speed. The IAC system controls idle speed by allowing a certain amount of air to by-pass the throttle body (throttle plate closed during idle) through the IAC valve. The PCM controlled IAC motor moves a pintle in and out of IAC valve, varying the amount of air entering the intake manifold.

If engine idle speed is greater than the desired idle speed and all test conditions are met, the PCM will cycle the IAC valve and expect to see a change in the MAF sensor reading. If no change occurs DTC P1509 will set. If a change occurs indicating the IAC is responding, then DTC P0507 will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Start and idle engine. Turn off all accessories. Using scan tool, select MISC TESTS and select IAC SYSTEM. Command engine speed up to 1500 RPM, down to 500 RPM, then back to 1500 RPM while monitoring ENGINE SPEED display. If ENGINE SPEED display remains within 50 RPM of desired value for each RPM command, fault is not present. See DIAGNOSTIC AIDS. If engine speed is not within 50 RPM of desired value, go to next step.
3. Disconnect IAC valve. Install IAC Noid Light (J 37027). Start engine. Command engine speed up to 1500 RPM, down to 700 RPM, then back to 1500 RPM while monitoring noid light. If noid light cycles Red and Green (never off), go to step 5). If noid light does not cycle, go to next step.
4. Check all IAC circuits for open, short to ground or short to voltage. Repair as necessary. If circuits are okay, go to step 8).
5. Check throttle body for objects blocking IAC passage or throttle bore, excessive deposits in IAC passage, pintle, throttle bore or throttle plate. Check for restriction or vacuum leaks in air intake system. Check adjustment screw for tampering. Repair as necessary. If no problems are found, go to next step.
6. Check for poor terminal contact at IAC harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
7. Replace IAC valve.
8. Check IAC terminal contacts at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
9. Replace PCM. Program replacement PCM using required equipment.

Reviewing the FAILURE REC may help diagnose an intermittent failure by showing how long ago and under what conditions the DTC set.

Vehicle uses an electronic gear indicator display. The PCM uses the combination of the switch patterns to determine the gear selected by the vehicle operator. This information is then sent by serial data to the IPC for gear indicator display.

This test monitors the transaxle range switch for false inputs. DTC will set if the transaxle range switch is indicating a gear that the PCM does not recognize or the transaxle range switch input does not match the input of the transaxle pressure switch.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Ensure Park/Neutral switch and shift cable/lever are properly adjusted. Block drive wheels and apply parking brakes. Start engine. Move shift lever through each range and observe TRANS. RANGE and SEL. LEVER SW. in ENGINE 3 mode on scan tool. If scan tool displays match each other for the range selected, fault is not present. See DIAGNOSTICS AIDS. If scan tool display does not match the range selected, go to next step.
3. If only TRANS. RANGE display matches each range selected, go to next step. If range selected does not match TRANS. RANGE display, diagnose using transmission DTC P1810. See the AUTO TRANS DIAGNOSIS article.
4. Turn ignition on, with engine off. Using scan tool in ENGINE 3 mode, observe SEL. LEVER SW A/B/C/P display. If all modes displays ON, go to step 13). If not all of the modes displays ON, go to next step.
5. If any of the modes (A/B/C/P) stays on or off all of the time, regardless of selector position, go to next step. If only some of the modes stays on or off all the time regardless of selector position, go to step 15).
6. If the mode(s) that did not change always display ON, go to step 9). If it displays OFF, go to next step.
7. Store fluid life index as indicated on scan tool. Turn ignition to LOCK position and wait 30 seconds, then disconnect PCM harness connector C1 and transaxle range switch. Using DVOM, check resistance between ground and the circuit that were always off. Resistance should be 5 ohms. If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, go to step 11).
8. Repair short to ground on the affected circuits with low or no resistance.
9. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1 and transaxle range switch. Using DVOM, check resistance between the transaxle switch connector and PCM harness connector C1 terminals on the circuit(s) that were always on. Resistance should be 5 ohms. If resistance is greater than 5 ohms, go to next step. If resistance is not greater than 5 ohms, go to step 12).
10. Repair open in the circuit(s) that have high or infinite resistance.
11. Reconnect PCM harness connector C1. Turn ignition on. Note SEL. LEVER SW A/B/C/P display on scan tool. If all the modes indicate ON, go to step 16). If not all modes indicate ON, go to step 17).
12. Reconnect PCM harness connector C1. Turn ignition on. Note SEL. LEVER SW A/B/C/P display on scan tool. Connect jumper wire between ground and the transaxle range switch harness connector terminal circuits that were always on. If scan tool display changes from ON to OFF when circuit is jumpered, go to step 15). If scan tool display does not indicate a change from ON to OFF when circuit is jumpered, go to step 17).
13. Turn ignition off. Disconnect transaxle range switch ground connector. Using DVOM, check resistance of ground connector to chassis ground. If resistance is 5 ohms or less, go to step 15). If resistance is not 5 ohms or less, go to next step.
14. Repair open or high resistance in ground circuit to transaxle range switch.
15. Check terminal contact at transaxle range switch. Repair as necessary. If terminal contact is okay, go to next step.
16. Replace transaxle range switch.
17. Check terminal contact at PCM. Repair as necessary. If terminal is okay, go to next step.
18. Replace PCM. Program replacement PCM using required equipment.

Check shifter for normal freedom of movement. The gear select indicator (PRNDL) in the IPC will flash on and off if an invalid or suspect gear position is received by the PCM. This will normally occur if the gear selector is not fully in a gear position. When a valid gear position is attained, the gear select display will immediately display the correct position. If the PRNDL on the IPC is flashing, this may be an indication that the shift cable and/or the transaxle range switch is out of adjustment.

On the scan tool, when checking the modes (circuits), OFF indicates that the circuit is low (switched/shorted to ground) and ON indicates that the circuit is high (Open). The snapshot data provides valuable information in diagnosing an intermittent DTC P1520. If all digits of the transaxle range input are on, then check for an intermittent loss of ground to transaxle range switch. If an intermittent DTC P1520 occurs when the transaxle shift lever is moved, DTC is most likely caused by a misadjustment of the shift linkage or range switch, causing range switch to end up in the position between gears.

If DTC sets and PRNDL in the IPC is flashing while driving or when drive gear selector is not being moved, record the transaxle lever position and compare the values from the chart. See TRANSAXLE RANGE SWITCH VALID INPUT COMBINATIONS chart. This will determine if circuit is open or shorted or intermittent.

DTC P1524 - TP SENSOR LEARNED CLOSED THROTTLE ANGLE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

The TP sensor is self-adjusting. When ignition is turned off, PCM executes a TP sensor learn routine. If the same correction factor occurs on 2 consecutive key off cycles, TP sensor is corrected to zero degrees, using the correction factor learned. If the value needs correction by greater than 6.8 degrees, DTC will be stored in PCM memory at the next key on cycle.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if «DTC P0121»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0121-tp-sensor-circuit) , P0122 or P0123 is present. If any of these DTC(s) are present, diagnose affected DTC(s) first. If these DTC(s) are not present, go to next step.
3. Select ENGINE 2 mode. Ensure foot is off accelerator pedal. Observe TP SENSOR display. If TP sensor reads 6.5 degrees or greater, go to step 5). If not, go to next step.
4. If TP sensor reads less than -6.5 degrees, go to step 8). If not, go to next step.
5. Check for binding throttle and cruise control cables. Repair as necessary. After repairs, go to step 9). If throttle and cruise control cables are okay, go to next step.
6. Check for deposits on throttle body bore and blades. Clean as necessary. After cleaning throttle body, go to step 9). If throttle body did not need cleaning, go to next step.
7. Turn ignition on. Using scan tool, select ENGINE 2. Ensure foot is off accelerator pedal. Observe TP SENSOR display. If reading outside of a range of -6.5 to 6.5 degrees, go to next step. If reading is as specified, go to step 9).
8. Replace throttle body. After replacing throttle body, go to next step.
9. Perform "TP Learn Procedure".

DTC P1527 - TRANSAXLE RANGE/PRESSURE SWITCH COMPARISON

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

Circuit Description - An electronic gear indicator display is used. There are 4 inputs which are switches to ground, that each have a unique switch pattern. All 4 of these inputs are housed and operate together in the transaxle range switch. PCM uses the combination of the switch patterns to determine the gear selected by the driver. This information is then sent by serial data to the IPC for gear indicator display. This test compares the gear indicated by the transaxle range switch to the gear selected from the transmission fluid pressure manual valve position switch. If gear indicated is not the same for both, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Ensure P/N position switch and shift cable/lever are adjusted properly. Set parking brake and block drive wheels. Start engine. Move shift lever through each range and observe TFP switch (pressure) and transmission range on scan tool. If scan tool display matches each other for the range that is selected, fault is not present. See DIAGNOSTIC AIDS. If not, go to next step.
3. If TFP switch matches each range selected, go to next step. If not, go to step 17).
4. Turn ignition on. Using scan tool, observe Trans Range A/B/C/P display. If all the modes display ON (High), go to step 13). If not, go to next step.
5. If any of the modes (A/B/C/P) stay ON (high) or OFF (low) all the time regardless of selector position, go to next step. If not, go to step 15).
6. If the mode(s) that did not change would always display ON (high), go to step 9). If not, go to next step.
7. Store fluid life data. Turn ignition off. Wait 30 seconds, then disconnect PCM harness connector. Disconnect transaxle range switch. Using DVOM, check resistance between ground on the circuit(s) that were always OFF (low). Mode A is circuit No. 771 Mode B is circuit No. 772 Mode C is circuit No. 773 Mode P is circuit No. 776 If resistance on tested circuit(s) is less than 5 ohms, go to next step. If not, go to step 11).
8. Repair short to ground in circuit(s) that have low or no resistance to ground.
9. Store fluid life data. Turn ignition off. Wait 30 seconds, then disconnect PCM harness connector. Disconnect transaxle range switch. Using DVOM, check resistance between transaxle range switch connector and PCM harness connector C1 terminals on circuit(s) that were always ON (high). Mode A is circuit No. 771 Mode B is circuit No. 772 Mode C is circuit No. 773 Mode P is circuit No. 776 If resistance on tested circuit(s) is greater than 5 ohms, go to next step. If not, go to step 12).
10. Repair open in circuit(s) that have high or infinite resistance.
11. Reconnect PCM harness connector (leave transaxle range switch disconnected). Turn ignition on. Check Trans Range A/B/C/P display. If all modes indicate ON (high), go to step 16). If not, go to step 23).
12. Reconnect PCM harness connector (leave transaxle range switch disconnected). Turn ignition on. Check Trans Range A/B/C/P display. Using jumper wire, jumper transaxle range switch connector circuit that was always ON (high) to ground. If display changes from ON to OFF when circuit is jumpered, go to step 15). If not, go to step 23).
13. Turn ignition off. Disconnect transaxle range switch ground connector. Check resistance to ground in circuit No. 451. If resistance is 5 ohms or less, go to step 15). If not, go to next step.
14. Repair open or high resistance in circuit No. 451.
15. Check for 2 or more mode circuits shorted together. Repair as necessary. If circuit is okay, check terminal contact at transaxle range switch. If terminal contact is okay, go to next step.
16. Replace transaxle range switch.
17. If DTC P1810 is also present, diagnose using transmission DTC P1810. See the AUTO TRANS DIAGNOSIS article. If DTC P1810 is not present, go to next step.
18. Start engine. Check if Trans Range (pressure) match in P, R, N and D4, but not in D1, D2 and D3. If pressure matches, go to step 20). If pressure does not match, go to next step.
19. Replace transmission fluid pressure manual valve position switch assembly.
20. Disconnect transaxle 20-pin harness connector. Shift through all gear ranges. If scan tool display ALWAYS indicate P/N, go to next step. If not, go to step 22).
21. Check transaxle range B input circuit between transaxle 20-pin harness connector and PCM for short to ground. Repair as necessary. If circuit is okay, go to step 23).
22. Check for short to ground between transaxle 20-pin connector and transmission fluid pressure manual valve position switch or for a faulty fluid pressure manual valve position switch. Repair or replace as necessary.
23. Check terminal contact at PCM. Repair as necessary. If terminal contact is okay, go to next step.
24. Replace PCM. Program replacement PCM using required equipment.

The modes (circuits) are displayed in the order of A/B/C/P. OFF indicates the circuit is low (switched/shorted to ground). ON indicates the circuit is high (open).

Manipulate related wiring and connectors while observing the transaxle range switch input. If an intermittent is induced, the digit corresponding the circuit will change. Use the Failure Records to help determine which switch was reading incorrectly. If the DTC set and the pressure switch indicated D1 and the select lever switch indicated P/N and the engine sensors (MAP, TP, MAF, etc.) appear to indicate that the vehicle was in Park or Neutral, then check the pressure switch/circuits for an intermittent fault.

DTC P1554 - CRUISE ENGAGED WITH CIRCUIT VOLTAGE HIGH

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM will not allow cruise control operation under certain conditions, such as when vehicle speed is too low. This is done by the PCM grounding the 12 volt cruise inhibit switch sent by the cruise control module. If PCM is allowing cruise operation and the operator is requesting for cruise control, the cruise control module will send a cruise engaged signal to the PCM.

This test is used to compare the cruise inhibit output versus the cruise engaged input. DTC will set when the PCM sees that the cruise control module is signaling that it is engaged by sending 12 volts to the cruise engaged circuit while the PCM is inhibiting cruise operation on the cruise inhibit output circuit.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if «DTC P1564»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p1564-cruise-control-system) is also present. If DTC P1564 is present, diagnose DTC first. If DTC P1564 is not present, go to next step.
3. Turn ignition on. Using scan tool, select DTC INFO. If DTC P1554 has failed this ignition, go to next step. If scan tool indicates DTC did not fail this ignition, fault is not present. See DIAGNOSTIC AIDS.
4. Turn ignition off. Disconnect cruise control module harness connector. Turn ignition on. Using scan tool, select DTC INFO. If DTC P1554 has failed this ignition, go to step 7). If scan tool indicates DTC did not fail this ignition, go to next step.
5. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Turn ignition on. Using DVOM, check resistance between ground and cruise engaged output circuit terminal at cruise module. If resistance is less than 10,000 ohms, go to next step. If not, go to step 8).
6. Repair short to ground in cruise engaged input circuit.
7. Replace cruise control module.
8. Replace PCM. Program replacement PCM using required equipment.

Use of the FAILURE REC. mode on scan tool can help diagnose intermittent problems, by displaying how long ago and the conditions under which the DTC set. Use of CRUISE REQUESTED and CRUISE displays can be monitored at the same time to aid in diagnosis an intermittent fault. Clear DTC and operate vehicle under the conditions in which the DTC set.

DTC P1560 - CRUISE CONTROL SYSTEM TRANSAXLE NOT IN DRIVE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

If the PCM is allowing cruise control operation and the operator requests cruise, the cruise control module will send a cruise engaged signal to the PCM. This test will set DTC if the cruise control is engaged and the transaxle pressure switch in indicating that the transaxle is in Park or Neutral. Cruise will disengage when transaxle is shifted out of a drive gear while cruise control is engaged.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P1520, DTC P1554 or Transmission DTC P1810 is also present. If any of the DTC(s) are present, diagnose affected DTC(s) first. For transmission DTC P1810, See the AUTO TRANS DIAGNOSIS article. If DTC(s) are not present, go to next step.
3. Verify if transaxle was shifted into Park or Neutral while cruise control was engaged. If transaxle was shifted out of a drive gear, causing DTC to set, go to next step. If transaxle was not shifted out of a drive gear, see DIAGNOSTIC AIDS.
4. Clear DTC. Explain to vehicle operator that shifting transaxle out of a drive gear while cruise control is engaged will set DTC.

Shifting into Neutral while cruise control is engaged will set this DTC. If this DTC was not induced by vehicle operator, use FAILURE REC on scan tool to compare both the TRANS RANGE and PNP displays to verify that operator did not induce DTC. Also, compare both displays to see if transaxle pressure switch circuit may have an intermittent fault. Clear DTC and operate vehicle under the conditions in which the DTC set.

DTC P1564 - CRUISE CONTROL SYSTEM VEHICLE ACCELERATION TOO HIGH

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

DTC will set when vehicle speed is increasing at an extremely rapid rate (wheelspin). Cruise control disables the cruise control when the vehicle suddenly accelerates, such as when traveling on icy roads. DTC being set under this condition is considered normal. Clear DTC and road test vehicle to verify normal operation.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if Transmission DTC P0503 is also present. If DTC P0503 is present, diagnose affected DTC first. See the AUTO TRANS DIAGNOSIS article. If DTC P0503 is not present, go to next step.
3. Verify if DTC was set by wheelspin due to icy, wet or slippery conditions. If road conditions caused DTC to set, go to next step. If not, fault is not present. See DIAGNOSTIC AIDS.
4. Clear DTC. Explain to vehicle operator what caused DTC to set.

Use of the FAILURE REC on scan tool can help diagnose intermittent problems, by displaying how long ago and the conditions under which the DTC set. Clear DTC and operate vehicle under the conditions in which DTC was set.

DTC P1566 - CRUISE CONTROL SYSTEM ENGINE RPM TOO HIGH

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

DTC will set if engine speed exceeds 5975 RPM while cruise control is engaged. This may occur on slippery pavement, extended wide open throttle acceleration or slipping transaxle. Cruise control disengaging because of these conditions is considered normal. Clear DTC and road test vehicle to verify normal operation.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Verify if DTC was set by wheelspin due to icy, wet or slippery conditions. If road conditions caused DTC to set, go to step 4). If not, go to next step.
3. Check for mechanical problems, such as transaxle slippage. Repair as necessary. If a mechanical problem is not present, see DIAGNOSTIC AIDS.
4. Clear DTC. Explain to vehicle operator what caused DTC to set.

Use of the FAILURE REC on scan tool can help diagnose intermittent problems, by displaying how long ago and the conditions under which the DTC set. Clear DTC and operate vehicle under the conditions in which DTC was set.

DTC P1570 - CRUISE CONTROL SYSTEM TRACTION CONTROL ACTIVE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test indicates that cruise control and traction control are active at the same time. It is a protective measure to disable the cruise control when traveling on icy roads and traction control requesting a maximum torque of less than one percent. Under these conditions DTC P1570 is set and the cruise control will be disengaged. Vehicle operator should be advised why cruise control disengaged.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if any traction control related DTC(s) are present. If DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
3. Since this DTC was caused most likely by wheel spin due to icy, wet or slippery road conditions, check with vehicle operator when DTC was set. If road condition caused DTC to set, go to next step. If road condition did not cause DTC to set, fault is not present. See DIAGNOSTIC AIDS.
4. Explain to vehicle operator the system operation. Clear DTC.

Use of the FAILURE REC. on scan tool can help diagnose intermittent problems, by displaying how long ago and the conditions under which the DTC set. Clear DTC and operate vehicle under the conditions in which it set, if fault condition is suspected.

DTC P1571 - TRACTION CONTROL SYSTEM PULSE WIDTH MODULATED (PWM) CIRCUIT NO FREQUENCY

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for traction control system PWM signal failure to the PCM. The PCM sends 12 volts on the desired torque circuit to the Electronic Brake and Traction Control Module (EBTCM). The EBTCM then rapidly switches this circuit to ground creating a PWM (frequency) signal to request a specific amount of torque reduction during a traction control maneuver. If this PWM signal is not received by the PCM for 3 seconds, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check for ABS/TCS related DTC(s). If DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
3. Check for intermittent terminal connection, intermittent open or short to the desired torque PWM input circuit between PCM connector C2 and EBTCM harness connector terminals. Repair as necessary. If circuit or terminal is okay, fault is not present. See DIAGNOSTIC AIDS.

If no fault is present, diagnose ABS/TCS system using the BRAKE SYSTEM - ANTI-LOCK article.

DTC P1574 - EBTCM SYSTEM STOP LIGHT SWITCH CIRCUIT VOLTAGE HIGH

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test functions on the assumption that a sudden decrease in non-drive wheel speed must be caused by a brake application. Non-drive wheel speed and stop light switch status are supplied to the PCM through the serial data from the EBTCM. If there is a 2.5 MPH or greater decrease of non-drive wheel speed in .4 second and a transition of the TCC or extended travel contacts of the TCC brake switch occurs without a transition of the stop light switch, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check of DTC P1602 is also present. If DTC P1602 is present, diagnose this DTC first. If DTC P1602 is not present, see DIAGNOSTIC AIDS.

DTC P1574 indicates that the stop light switch signal to the EBTCM or the EBTCM's ability to send the stop light switch signal to the PCM has failed. For further diagnosis refer to ABS/TCS DTC 74. See the BRAKES SYSTEM - ANTI-LOCK article in the BRAKES section.

DTC P1575 - EXTENDED TRAVEL BRAKE SWITCH CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test functions on the assumption that a sudden decrease in non-drive wheel speed must be caused by a brake application. Non-drive wheel speed and stop light switch status are supplied to the PCM through the serial data from the EBTCM. If there is a 2.5 MPH or greater decrease of non-drive wheel speed in .2 second and a transition of the TCC or extended travel contacts of the TCC brake switch occurs without a transition of the stop light switch, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool in ENGINE 1 mode, note EXT TRAVEL BRAKE display. If scan tool display indicates RELEASED, go to next step. If scan tool display does not indicate RELEASED, go to step 7).
3. Depress brake pedal about half way. If scan display indicates APPLIED, fault is not present. See DIAGNOSTIC AIDS. If scan tool display does not indicate APPLIED, go to next step.
4. Disconnect extended travel brake switch connector. If scan tool display indicates APPLIED, go to step 21). If scan tool display does not indicate APPLIED, go to next step.
5. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Turn ignition on. Using DVOM, check voltage between ground and TCC brake switch input circuit terminal at PCM harness connector C1. If voltage is greater than .5 volt, go to next step. If voltage is not greater than .5 volt, go to step 19).
6. Repair short to voltage between extended travel brake switch input circuit.
7. Note TCC BRAKE SWITCH display on scan tool. If scan tool display indicates RELEASED, go to next step. If scan tool display does not indicate RELEASED, go to step 11).
8. Disconnect extended travel brake switch harness connector. Using DVOM, check voltage between ground and extended travel brake switch terminal "C". If voltage reading is 10 volts or greater, go to next step. If voltage reading is not 10 volts or greater, go to step 17).
9. Using jumper wire, jumper extended travel brake switch terminals 'C" and "D". If scan tool display indicates RELEASED, go to step 21). If scan tool display does not indicate RELEASED, go to next step.
10. Store fluid index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Turn ignition on. Using DVOM, check voltage between ground and TCC brake switch input circuit at PCM harness connector C1 terminal. If voltage reading is 10 volts or greater, go to step 13). If voltage reading is not 10 volts or greater, go to step 18).
11. Check fuse to shift solenoid. If fuse is faulty, go to step 13). If fuse is okay, go to next step.
12. Disconnect extended travel brake switch connector. Using DVOM, check voltage between ground and extended travel brake switch connector terminal "C". If voltage reading is 10 volts or greater, go to step 21). If not, go to step 16).
13. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Using DVOM, individually check the resistance to all the extended travel switch connector terminals. If resistance is less than 100 ohms on any of the terminals, go to next step. If resistance is not less than 100 ohms on any of the terminals, go to step 15).
14. Repair short in the circuits with low resistance. Replace fuse.
15. Check for intermittent short to ground on both extended travel and TCC brake switch circuits. Repair as necessary. Replace fuse.
16. Repair open in circuit to EBTCM.
17. Repair open in circuit to shift solenoid fuse.
18. Repair open in circuit between switch and EBTCM.
19. Check terminal contact at PCM harness connector C1. Repair as necessary. If terminal contact is okay, go to next step.
20. Replace PCM. Program replacement PCM using required equipment.
21. Check for proper adjustment of extended travel brake switch. Adjust as necessary. If adjustment was not necessary, go to next step.
22. Replace extended travel brake switch.

Use FAILURE REC. information on scan tool to help diagnose an intermittent problem. The operating conditions as well as the state of the extended travel brake switch circuit will be stored when the DTC was set.

DTC P1576 - BRAKE BOOSTER VACUUM (BBV) SENSOR CIRCUIT VOLTAGE HIGH

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

The BBV sensor changes resistance based on the vacuum inside the brake booster. This test checks for a vacuum sensor reading caused by a shorted sensor, a short in BBV sensor signal circuit or a short in the BBV sensor ground circuit. Every time the TCC brake switch cycles from closed to open with engine not at idle, this test checks for a shorted vacuum signal. This test will not fail unless 5 consecutive cycles of the TCC brake switch with 82 kPa is monitored. Any cycle of the TCC brake switch where a shorted vacuum signal is not detected will reset the counter to zero.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool in ENGINE 3 mode, note BRAKE BOOST VAC display. If scan tool displayed value is 82 kPa or greater, go to next step. If scan tool displayed value is not 82 kPa or greater, fault is not present. See DIAGNOSTIC AIDS.
3. Disconnect BBV sensor harness connector. If scan tool displayed value is -7 kPa or greater, go to next step. If not, go to step 5).
4. Store fluid life index as indicated on scan tool. Turn ignition to LOCK position and wait 30 seconds, then disconnect PCM harness connector C1. Turn ignition on. Using DVOM, check voltage between ground and BBV sensor signal circuit terminal. If voltage reading is .4 volt or less, go to step 12). If not, go to step 7).
5. Store fluid life index as indicated on scan tool. Turn ignition to LOCK position and wait 30 seconds, then disconnect PCM harness connector C1. Turn ignition on. Using DVOM, check BBV sensor ground circuit resistance between PCM harness connector C1 and BBV sensor harness connector terminal. If resistance is 5 ohms or less, go to next step. If not, go to step 9).
6. Reconnect PCM harness connector C1. Turn ignition on. Check voltage between BBV sensor harness connector terminals "B" and "C". If voltage is less than 5.4 volts, go to step 10). If not, go to step 8).
7. Repair short to voltage in BBV sensor signal circuit between PCM and BBV sensor.
8. Repair short to voltage in BBV 5-volt reference circuit between PCM and BBV sensor.
9. Repair open in BBV sensor ground circuit between PCM and BBV sensor.
10. Check terminal contact at BBV sensor harness connector. Repair as necessary. If terminal contact is okay, go to next step.
11. Replace BBV sensor.
12. Check terminal contact at PCM harness connector C1. Repair as necessary. If terminal contact is okay, go to next step.
13. Replace PCM. Program replacement PCM using required equipment.

Use the FAILURE REC. information on scan tool to help diagnose an intermittent problem. Manipulate wire harness while watching scan tool display, looking for an open or shorted circuit.

DTC P1577 - BRAKE BOOSTER VACUUM (BBV) SENSOR CIRCUIT LOW VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

The BBV sensor changes resistance based on the vacuum inside the brake booster. This test checks for a vacuum sensor reading caused by an open sensor, an open in BBV sensor signal circuit or an open in the BBV sensor ground circuit. When PCM detects a brake booster vacuum signal that is too low, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool in ENGINE 3 mode, note BRAKE BOOST VAC display. If scan tool displayed value is -7 kPa or greater, fault is not present. See DIAGNOSTIC AIDS. If not, go to next step.
3. Disconnect BBV sensor harness connector. Jumper BBV sensor connector terminals "B" and "C". If scan tool displayed value is -7 kPa or greater, go to step 13). If not, go to next step.
4. Remove jumper wire. Using DVOM, check voltage between ground and BBV harness connector terminal "C". If voltage reading is 4.5 volts or greater, go to next step. If not, go to step 7).
5. Store fluid life index as indicated on scan tool. Turn ignition to LOCK position and wait 30 seconds, then disconnect PCM harness connector C1. Using DVOM, check resistance between ground and BBV sensor signal circuit terminal. If resistance is 100 ohms or less, go to step 12). If not, go to next step.
6. Check resistance of BBV sensor signal circuit between PCM harness connector C1 and BBV harness connector terminals. If resistance is 5 ohms or greater, go to step 15). If not, go to step 11).
7. Store fluid life index as indicated on scan tool. Turn ignition to LOCK position and wait 30 seconds, then disconnect PCM harness connector C1. Using DVOM, check BBV sensor 5-volt reference circuit resistance between PCM harness connector C1 and BBV sensor harness connector terminal. If resistance is 100 ohms or less, go to step 10). If not, go to next step.

DTC P1578 - BRAKE BOOSTER VACUUM (BBV) SENSOR CIRCUIT LOW VACUUM

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

The BBV sensor changes resistance based on the vacuum inside the brake booster. This test monitors the brake booster vacuum along with the manifold vacuum (calculated from MAP). If brake booster vacuum is too low for a given manifold vacuum and brakes are not applied, the brake booster vacuum signal must be in error and DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool in ENGINE 3 mode, note BRAKE BOOST VAC display. If scan tool displayed value is greater than 5 kPa, fault is not present. See DIAGNOSTIC AIDS. If not, go to next step.
3. Start and idle engine. Check vacuum to brake booster using a vacuum gauge. If vacuum reading is 14 in. Hg or greater, go to next step. If not, go to step 15).
4. Turn ignition on, with engine off. Disconnect BBV sensor harness connector. Jumper BBV sensor connector terminals "B" and "C". If scan tool displayed value is 81 kPa or less, go to next step. If not, go to step 11).
5. Using DVOM, check voltage between ground and jumper wire. If voltage is less than .5 volt, go to next step. If not, go to step 7).
6. Remove jumper wire. Using DVOM, check voltage between ground and BBV harness connector terminal "C". If voltage reading is 4.5 volts or greater, go to step 9). If not, go to step 10).
7. Store fluid life index as indicated on scan tool. Turn ignition to LOCK position and wait 30 seconds, then disconnect PCM harness connector C1. Using DVOM, check resistance between ground and BBV sensor signal circuit terminal. If resistance is 5 ohms or less, go to step 13). If not, go to next step.
8. Repair open or high resistance in BBV sensor signal circuit between PCM and BBV sensor.
9. Repair short to ground in BBV sensor signal between PCM and BBV sensor.
10. Repair open or short in BBV sensor 5-volt reference circuit between PCM and BBV sensor.
11. Check terminal contact at BBV sensor harness connector. Repair as necessary. If terminal contact is okay, go to next step.
12. Replace BBV sensor.
13. Check terminal contact at PCM harness connector C1. Repair as necessary. If terminal contact is okay, go to next step.
14. Replace PCM. Program replacement PCM using required equipment.
15. Locate and repair cause of low vacuum at brake booster. Repair as necessary.

Use the FAILURE REC. information on scan tool to help diagnose an intermittent problem. Manipulate wire harness while watching scan tool display, looking for an open or shorted circuit.

DTC P1579 - PARK/NEUTRAL-TO-DRIVE/REVERSE AT HIGH THROTTLE ANGLE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test is used to detect if transaxle is placed in gear under conditions that may cause damage to vehicle powertrain or create an unsafe condition. When such condition exists, DTC will set and engine power will be reduced by disabling fuel injector to individual cylinders.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Since this DTC will set when the vehicle is shifted into Drive/Reverse under possibly damaging conditions, check with vehicle operator to verify under which condition the DTC set. If vehicle operator actions caused this DTC to set, fault is not present. See DIAGNOSTIC AIDS. If vehicle operator did not cause DTC to set, go to next step.
3. Check for proper adjustment of transaxle range switch and for poor terminal contact at switch and the PCM. Repair as necessary. If adjustment or terminal contact is okay, fault is not present. See DIAGNOSTIC AIDS.

If driver's action caused the DTC to set, clear DTC and inform driver of proper shift procedure.

Use FAILURE REC. information on scan tool to help diagnose an intermittent problem. Manipulate wiring harness while watching scan tool display, looking of an open or short in circuit.

DTC P1599 - ENGINE STALL OR NEAR STALL DETECTED

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for an engine stall or near stall and sets DTC P1599 if a stall condition is detected. A partial start when engine RPM exceeds 400 RPM and the engine does not start, will also cause DTC to set. This DTC is designed to capture snapshot data of the stall condition and may set as the ignition is turned off, if the injectors or IC module lose power before the PCM.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. If complaint is engine stalling, go to next step. If engine is not stalling, fault is not present. See DIAGNOSTIC AIDS.
3. Turn ignition on. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
4. Select DATA LIST under SPECIFIC ENGINE and select DTC P1599. Note MAP sensor display taken at the time this DTC was set. If scan tool displayed value is greater than 95 kPa, go to next step. If scan tool displayed value is not greater than 95 kPa, see the TESTS W/O CODES article.
5. Stalling can be caused by either fuel system, idle speed control, emissions related components or faulty wiring and connections. Perform fuel system check. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. Repair as necessary. If fault is not found or if related systems are okay, go to next step.
6. Check for TCC that is improperly applied due to grounded TCC solenoid circuit or by transaxle hydraulic problems. For diagnosis of hydraulic problems, see the TRANSMISSION SERVICING article. Check ignition switch circuits for intermittent open to PCM or IC module. Wiggle ignition key while driving to check for intermittent ignition switch connection or switch out of adjustment. Check PCM and IC module ground. Check for intermittent injector circuit operation. Check fuel pump ground for loose or poor connection. Repair as necessary. If repair was not necessary, see DIAGNOSTIC AIDS.

Use scan tool snapshot data taken of DTC P1599 to determine cause of stalling condition.

DTC P1602 - LOSS OF EBTCM SERIAL DATA

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for absent or invalid EBTCM serial data to the PCM. When such conditions exists for 11 seconds, DTC will set.

Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING article. After performing OBD system check, diagnose ABS/TCS system. See the BRAKE SYSTEM - ANTI-LOCK article in the BRAKES section.

DTC P1603 - LOSS OF SENSING DIAGNOSTIC MODULE SERIAL DATA

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for loss of or invalid Sensing Diagnostic Module (SDM) serial data to the PCM. When such condition exists for one second, DTC will set.

Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING article. After performing OBD system check, diagnose air bag (SIR) system. See the AIR BAG RESTRAINT SYSTEM article in the ACCESSORIES/SAFETY EQUIPMENT section.

DTC P1604 - LOSS OF INSTRUMENT PANEL CLUSTER SERIAL DATA

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for loss of or invalid Instrument Panel Cluster (IPC) serial data to the PCM. When such condition exists for 11 seconds, DTC will set.

Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING article. After performing OBD system check, diagnose IPC. See the INSTRUMENT PANELS article in the ACCESSORIES/SAFETY EQUIPMENT section.

DTC P1605 - LOSS OF HVAC SERIAL DATA

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for loss of or invalid Heater and A/C (HVAC) programmer serial data to the PCM. When such condition exists for 11 seconds, DTC will set.

Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING article. After performing OBD system check, diagnose Electronic Climate Control (ECC) or A/C-heater system using the A/C-HEATER SYSTEM article.

DTC P1610 - LOSS OF PZM SERIAL DATA

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for the loss of or invalid Platform Zone Module (PZM) serial data to the PCM. When such condition exists for 11 seconds, DTC will set.

Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING article. After performing OBD system check, check PZM serial data line for open or short to ground.

DTC P1611 - LOSS OF CVRTD SERIAL DATA

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for absent or invalid Continuous Variable Real Time Damping (CVRTD) system serial data to the PCM. When such condition exists for 11 seconds, DTC will set.

Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING article. After performing OBD system check, check CVRTD system serial data line for open or short to ground.

EEPROM is a data storage unit which can save critical data even battery power is removed. This is used by the PCM to store TP sensor idle learned values, transaxle adapt values, transaxle oil life index and cruise control lash/learn.

The EEPROM has several locations available to store this information. If PCM detects a problem in one location of the EEPROM, it will store the data in another location. If PCM runs out of good locations in the EEPROM to store data, it will set the DTC.

The PCM stores the same data in its Keep Alive Memory so that even if the EEPROM is bad and DTC is set, the operator will not notice any difference in vehicle operation. Even after DTC sets, the PCM will continue to look for good locations in the EEPROM in which to store data and if it finds one, DTC will become a history code. EEPROM is soldered into the PCM and cannot be serviced. If a current DTC P1621 is set, PCM must be replaced.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select DTC INFO and select FAIL THIS IGN. If DTC failed this ignition, go to step 4). If not, go to next step.
3. Clear DTC P1621. Cycle ignition on and off several times slowly. Turn ignition on for 10 seconds, then turn ignition off for 30 seconds. Using scan tool, view DTC INFO and select TEST FAIL SCC. If this DTC failed since DTCs were cleared, go to next step. If not, fault is not present.
4. Replace PCM. Program replacement PCM using required equipment.

DTC P1626 - THEFT DETERRENT SYSTEM FUEL ENABLE CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

After the key resistor pellet has been confirmed by the PASS-Key(R) portion of the Vehicle Theft Deterrent (VTD) system, the IPC sends a password to the PCM via the class 2 serial data bus. If password matches the password stored in the PCM, fuel will be enabled. If IPC does not send a password or if PCM doesn't receive it, vehicle will not start unless VTD has the fuel enabled.

If IPC and PCM loose communication with each other while engine is running, VTD system will fail-enable and allow driver to restart the vehicle on future ignition cycles until communications between the IPC and PCM are restored. If battery is disconnected during this period, vehicle will loose its fail-enabled status and will no longer start until communications has been re-established.

If IPC and PCM loose communications with each other while engine is not running, VTD system will disable fuel until communications is restored to prevent vehicle theft.

In both cases, DTC P1626 will be set. The PCM will not disable fuel injection once it has been enabled within a given ignition cycle to prevent stalling as a result of VTD system faults.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Check if «DTC P1604»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p1604-loss-of-instrument) is also present. If DTC P1604 is present, diagnose using P1604 tests. If not, go to next step.
3. Check for VTD or IPC DTCs. If DTCs are present, diagnose DTCs first. If DTCs are not present, see DIAGNOSTIC AIDS.

The most likely cause of DTC P1626 is a loss of serial data communication to the IPC. Check for loss of power to IPC or for other causes of communication loss.

DTC P1630 - THEFT DETERRENT SYSTEM PCM IN LEARN MODE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for the enable password learning flag indicating the PCM is in learn password mode. This mode allows the PCM to learn the password from the VTD controller at assembly or when being serviced. The password needs to be learned whenever PCM or IPC is replaced.

Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING article. After performing OBD system check, refer to DIAGNOSTIC AIDS.

The PCM in learn mode is a DTC for the vehicle at the assembly plant or repair facility personnel to indicate that the learn mode is enabled, meaning that the PCM is now ready to learn a new password.

DTC P1631 - THEFT DETERRENT SYSTEM PASSWORD INCORRECT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This test checks for mismatched passwords between the IPC and PCM. Whenever the IPC or PCM are replaced, a theft learn procedure must be followed in order for the new password to be learned.

Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING article. After performing OBD system check, perform theft learn procedure. See the ANTI-THEFT SYSTEM article in the ACCESSORIES/SAFETY EQUIPMENT section.

DTC P1632 - THEFT DETERRENT SYSTEM FUEL DISABLED

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

This DTC sets when the PCM received fuel disabled or fuel undecided passwords from the Vehicle Theft Deterrent (VTD) controller. It is set as a tool to indicate that the VTD is not allowing fuel due to possible theft attempt or a worn or incorrect ignition key.

Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING article. After performing OBD system check, refer to DIAGNOSTIC AIDS.

If DTC is set, it means that the IPC has received the incorrect resistance value or an unrecognizable resistance value from the ignition key. Check ignition key to ensure it is the correct key for the vehicle and that it is clean and dry. Wait 10 minutes between attempts to clean and retry key. This DTC will also set when a theft is attempted.

DTC P1633 - IGNITION SUPPLEMENT POWER CIRCUIT VOLTAGE LOW

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM is powered by 5 power feeds. Two of these feed are from the battery, the other 3 are from the ignition switch and are called Ignition 1, Ignition 0 and Ignition Supplement. The ignition feeds are powered any time the key is in the CRANK, RUN or ACC positions. This test is used to monitor the ignition supplement voltage received at the PCM connector C2, terminal No. 37. PCM monitors this voltage and if voltage drops too low for one second, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Using scan tool, check if «DTC P1634»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p1634-ignition-1-power) is also present. If DTC P1634 is also present, diagnose this DTC first. If DTC P1634 is not present, go to next step.
3. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and ignition feed circuit at PCM harness connector C2, terminal No. 37. Using scan tool, note and write down IGNITION 1 voltage reading. If DVOM and scan tool voltage readings are within .5 volt of each other, go to next step. If not, go to step 5).
4. Turn ignition off. Reconnect PCM harness connector C2. Turn ignition on. Using scan tool, clear DTC. Start and idle engine. After 10 seconds in DTC INFO mode, select FAIL THIS IGN. If DTC failed in this ignition cycle, go to step 6). If DTC did not fail in this ignition cycle, fault is not present. See DIAGNOSTIC AIDS.
5. Repair open in ignition feed circuit between PCM harness connector and splice.
6. Check terminal contact at PCM harness connector C2, terminal No. 37. Repair as necessary. If terminal contact is okay, go to next step.
7. Replace PCM. Program replacement PCM using required equipment.

If ignition supplement to the PCM is lost, the engine will still run, but some outputs may not function. If Ignition 1 voltage is lost or drops to less than 5.5 volts, engine will not run and DTC should set.

If this DTC is intermittent, check terminal contact at PCM and condition of splice for an intermittent open circuit.

DTC P1634 - IGNITION 1 POWER CIRCUIT LOW VOLTAGE

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM is powered with 5 power feeds. Two of these feeds are from the battery, the other 3 are from the ignition switch and are called ignition 1, ignition supplement and ignition 0. Ignition 1 and ignition supplement are powered any time the key in the CRANK, RUN or ACC positions. Ignition 0 is powered in all key positions except LOCK and CRANK.

This test is used to monitor the voltages received by the PCM at harness connector C1 terminals No. 18 and 19. When engine is running, PCM will compare Ignition 1 voltage it receives at PCM harness connector C1 terminal No. 19 to the Ignition 0 voltage it receives at PCM harness connector C1 terminal No. 18. If Ignition 1 and Ignition 0 voltage difference is greater than 2 volts for 5 seconds, DTC will set.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if «DTC P0560»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p0560-system-voltage-low) is also present. If DTC P0560 is present, diagnose DTC first. If DTC P0560 is not present, go to next step.
3. Using scan tool in ENGINE 1 mode, note both IGNITION 0 and IGNITION 1 displays. Compare both readings. If voltage difference is less than .5 volt, go to next step. If voltage difference is greater than .5 volt, go to step 5).
4. Clear DTC using scan tool. Start and idle engine. After 10 seconds in DTC INFO mode, select FAIL THIS IGN. If scan tool indicates that this DTC failed this ignition cycle, go to step 12). If scan tool does not indicate that this DTC failed this ignition cycle, fault is not present. See DIAGNOSTIC AIDS.
5. If Ignition 0 voltage was lower than Ignition 1 voltage, go to next step. If Ignition 0 voltage was greater than Ignition 1 voltage, go to step 7).
6. Check Ignition 0 fuse (IGN OIENG1). If fuse is faulty, go to step 10). If fuse is okay, go to step 9).
7. Check Ignition 1 fuse (PCM-IGN). If fuse is faulty, go to next step. If fuse is okay, go to step 11).
8. Repair short to ground in Ignition 1 and ignition supplement feed circuits. Replace fuse.
9. Repair open/high resistance or poor terminal contact at ignition 0 feed circuit.
10. Repair short to ground in Ignition 0 feed circuit. Replace fuse.
11. Repair open/high resistance or poor terminal contact at ignition 1 and ignition supplement feed circuits.
12. Check terminal contact at PCM harness connector C1. Repair as necessary. If terminal contact is okay, go to next step.
13. Replace PCM. Program replacement PCM using required equipment.

If the Ignition 0 to PCM is lost, vehicle will still run but some outputs may not function. If Ignition 1 voltage is lost or drops to less than 5.5 volt, vehicle will not run and DTC should set. If DTC is intermittent, check terminal contact at PCM and the condition of ignition feed circuit splice for an intermittent open.

DTC P1640 - DRIVER 1 - INPUT VOLTAGE HIGH

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM contains Output Driver Modules (ODM) that provides 7 switchable ground outputs for operating solenoids, relays, indicator lights, and other devices. Each of these ground outputs has fault lines that feed back to the PCM's microprocessor. ODM No. 1 can also sense high voltage coming in which might damage microprocessor. DTC P1640 is used to monitor ODM No. 1 over voltage sense line.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Start and idle engine. Using scan tool, select ENGINE 1 mode and note IGNITION 1 display. Compare this voltage reading with voltage reading displayed by vehicle message center. If PCM and vehicle voltage readings differ by greater than .5 volt, go to next step. If PCM and vehicle voltage readings is within .5 volt of each other, fault is not present. See DIAGNOSTIC AIDS.
3. Using DVOM, check voltage between ground and PCM fuse. If PCM fuse voltage and scan tool displayed voltage reading difference is greater than .5 volt, go to next step. If PCM fuse voltage and scan tool displayed voltage reading is within .5 volt of each other, check charging system. See the GENERATORS article in the ELECTRICAL section.
4. Check for high resistance is ignition feed circuits to PCM. Repair as necessary. If circuits are okay, go to next step.
5. Check terminal contacts at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
6. Replace PCM. Program replacement PCM using required equipment.

An overvoltage at ODM No. 1 will also trigger DTC P0563. Use DTC P0563 to diagnose if vehicle voltage is actually too high. A loose or faulty connection at generator "L" terminal may cause DTC P1640 to set intermittently.

DTC P1641 - MALFUNCTION INDICATOR LIGHT (MIL) CONTROL CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM contains Output Driver Modules (ODM) that provides 7 switchable ground outputs for operating solenoids, relays, indicator lights, and other devices. Each of these ground outputs has fault lines that feed back to the PCM's microprocessor. When the output is off, the output driver should receive the 12 volts fed to the solenoid, relay, etc. When the output is on, it should receive zero volts, since it is grounding the output. when PCM sees zero volts when the output is off or 12 volts when the output is on, it sets a fault line low. DTC P1641 is used to monitor the fault line of the SERVICE ENGINE SOON light.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Check if MIL illuminates after 5 seconds. If MIL illuminates, go to next step. If MIL does not illuminate, go to step 4).
3. Using scan tool, enter OUTPUT TESTS then select MIL. Command MIL off. If MIL turns off, fault is not present. See DIAGNOSTIC AIDS. If MIL does not turn off, go to step 8).
4. Select ENGINE 3 mode and note MALFUNCTION IND LAMP DRIVER display on scan tool. If scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 6).
5. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Remove IP cluster fuse. Turn ignition on. Using DVOM, check voltage between ground and MIL signal circuit at PCM harness connector C2. If voltage reading is .5 volt or greater, go to step 9). If voltage reading is not .5 volt or greater, go to step 13).
6. Reinstall IP cluster fuse. Using a jumper wire, jumper MIL signal circuit at PCM harness connector C2 to ground. If MIL illuminates, go to step 13). If MIL does not illuminate, go to next step.
7. Check condition of IP fuse. If fuse is faulty, go to step 10). If fuse is okay, go to step 13).
8. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. If MIL illuminates, go to step 12). If MIL does not illuminate, go to step 13).
9. Repair short to voltage in MIL signal circuit.
10. Repair short to ground in circuit between MIL and fuse block.
11. Repair open in MIL circuit from fuse block to PCM. Check for faulty MIL bulb.
12. Replace short to ground in MIL circuit between MIL bulb and PCM.
13. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal connector is okay, go to next step.
14. Replace PCM. Program replacement PCM using required equipment.

Use the FAILURE REC as indicated on scan tool to aid in diagnosing an intermittent fault. Use data captured when DTC was set, to determine if an open or shorted condition caused the DTC to set. Ensure no other DTC(s) are present, commanding MIL to illuminate.

DTC P1642 - VEHICLE SPEED OUTPUT CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM contains Output Driver Modules (ODMs) that provides 7 switchable ground outputs for operating solenoids, relays, indicator lights, and other devices. Each of these ground outputs has fault lines that feed back to the PCM's microprocessor. When the output is off, the output driver should receive the 12 volts fed to the solenoid, relay, etc. When the output is on, it should receive zero volts, since it is grounding the output. If PCM sees zero volts when the output is off or 12 volts when the output is on, it sets a fault line low.

DTC P1642 is used to monitor the fault line of the vehicle speed output signal circuit. The Instrument Panel Cluster (IPC) sends 12 volts on the vehicle speed output circuit to the PCM. The PCM sends a pulse width modulated signal that the IPC, cruise control module and Remote Accessory Control (RAC) module use to determine vehicle speed.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select ENGINE 3 mode and note VEHICLE SPEED DRIVER display. If scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 5).
3. Raise and support drive wheels. Start engine. Spin wheels for about 2 seconds to generate a vehicle speed signal. In DTC INFO mode, select FAIL THIS IGN on scan tool. If scan tool indicates that DTC failed in this ignition cycle, go to next step. If scan tool does not indicate that DTC failed in this ignition cycle, fault is not present. See DIAGNOSTIC AIDS.
4. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and vehicle speed output signal circuit at PCM harness connector C2. If voltage reading is 10 volts or greater, go to step 7). If not, go to next step.
5. Repair open or short in vehicle speed output circuit between PCM and IPC, and cruise control module and RAC module. Repair as necessary.
6. Repair short to voltage in vehicle speed output circuit between PCM and IPC, and cruise control module and RAC module. Repair as necessary.
7. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
8. Replace PCM. Program replacement PCM using required equipment.

Use the FAILURE REC indicated on scan tool to aid in diagnosing an intermittent fault. Use the data captured when the DTC was set to determine the conditions under which the DTC set.

DTC P1644 - DELIVERED TORQUE OUTPUT CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM contains Output Driver Modules (ODMs) that provides 7 switchable ground outputs for operating solenoids, relays, indicator lights, and other devices. Each of these ground outputs has fault lines that feed back to the PCM's microprocessor. When the output is off, the output driver should receive the 12 volts fed to the solenoid, relay, etc. When the output is on, it should receive zero volts, since it is grounding the output. If PCM sees zero volts when the output is off or 12 volts when the output is on, it sets a fault line low.

DTC P1644 is used to monitor the fault line of the delivered torque output to the EBTCM. The EBTCM sends ignition voltage on the delivered torque PWM output circuit to the PCM. The PCM will then rapidly pulse this circuit to ground creating a Pulse Width Modulated (PWM) signal, indicating the percentage of torque output the engine is producing. The EBTCM uses this PWM signal for traction control.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool in ENGINE 3 mode, observe DELIVERED TORQUE DRIVER display. If scan tool display indicates OK, fault is not present. See DIAGNOSTIC AIDS. If scan tool display does not indicate OK, go to next step.
3. If scan tool display indicates OPEN, go to next step. If scan tool display does not indicate OPEN, go to step 6).
4. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and delivered torque PWM output circuit at PCM harness connector C2. If voltage reading is 10 volts or greater, go to step 13). If not, go to next step.
5. Turn ignition to LOCK position. Disconnect EBTCM harness connector. Check resistance of delivered torque PWM output circuit between PCM harness connector and EBTCM harness connector terminals. If resistance is 5 ohms or less, go to step 12). If not, go to step 9).
6. Turn ignition to LOCK position. Disconnect EBTCM harness connector. Turn ignition on. If scan tool display indicates OPEN, go to step 12). If scan tool display does not indicate OPEN, go to next step.
7. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check resistance between ground and delivered torque PWM output circuit at PCM harness connector C2 terminal. If voltage is greater than .5 volt, go to step 10). If not, go to next step.
8. Using DVOM, check resistance between ground and delivered torque PWM output circuit at PCM harness connector C2 terminal. If resistance is 10,000 ohms or greater, go to step 13). If not, go to step 11).
9. Repair open in delivered torque PWM output circuit.
10. Repair short to voltage in delivered torque PWM output circuit.
11. Repair short to ground in delivered torque PWM output circuit.
12. Fault is in the EBTCM system. Diagnose EBTCM. See the BRAKES SYSTEM - ANTI-LOCK article in the BRAKES section. If fault is not found in EBTCM system, check for faulty terminal contact to EBTCM. If terminal contact is okay, replace EBTCM.
13. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
14. Replace PCM. Program replacement PCM using required equipment.

Check for an intermittent poor connection at both the PCM and EBTCM. Also, check for open or short in delivered torque PWM output circuit between EBTCM and PCM.

DTC P1645 - EVAP PURGE SOLENOID OUTPUT CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM contains Output Driver Modules (ODM) that provides 7 switchable ground outputs for operating solenoids, relays, indicator lights, and other devices. Each of these ground outputs has fault lines that feed back to the PCM's microprocessor. When the output is off, the output driver should receive the 12 volts fed to the solenoid, relay, etc. When the output is on, it should receive zero volts, since it is grounding the output. If PCM sees zero volts when the output is off or 12 volts when the output is on, it sets a fault line low. DTC is used to monitor the fault line of the EVAP control solenoid.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if «DTC P1633»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-tests-wcodes-46l__dtc-p1633-ignition-supplement-power) or P1644 is present. If any of the DTC is present, diagnose affected DTC first. If DTC P1653 or P1644 is not present, go to next step.
3. If DTC P0102, P0401, P0550, P0753, P0758, P1406 or P1860 is also present, go to step 10). If these DTC(s) are not present, go to next step.
4. Using scan tool, select ENGINE 3 and note EVAP PURGE SOL. DRIVER display. If scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 6).
5. Start and idle engine. Select OUTPUT TESTS and select EVAP PURGE. Command EVAP purge solenoid on (open) for at least 2 seconds. Note EVAP PURGE SOL. DRIVER display. If scan tool display indicates OK, fault is not present. See DIAGNOSTIC AIDS. If scan tool display does not indicate OK, go to step 9).
6. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and EVAP purge solenoid circuit at PCM harness connector C2. If voltage reading is 10 volts or greater, go to step 15). If not, go to next step.
7. Disconnect EVAP purge solenoid harness connector. Check voltage between ground and EVAP purge solenoid ignition circuit harness connector terminal. If voltage reading is 10 volts or greater, go to next step. If not, go to step 11).
8. Using jumper wire, jumper EVAP purge solenoid harness connector terminals together. Check voltage between ground and EVAP purge solenoid circuit at PCM harness connector terminal. If voltage reading is 10 volts or greater, go to step 12). If not, go to step 13).
9. Turn ignition off. Disconnect EVAP purge solenoid harness connector. Turn ignition on. Using DVOM, check voltage between ground and EVAP purge solenoid signal circuit harness connector terminal. If voltage is .5 volt or greater, go to step 14). If not, go to step 12).
10. Repair open or short in EVAP purge solenoid ignition circuit. Also, check for faulty fuse. Repair as necessary.
11. Repair open in EVAP purge solenoid ignition circuit and splice.
12. Replace EVAP purge solenoid.
13. Repair open in circuit between EVAP purge solenoid and PCM.
14. Repair short to voltage in circuit between EVAP purge solenoid and PCM.
15. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
16. Replace PCM. Program replacement PCM using required equipment.

Use the FAILURE REC. on scan tool to aid in diagnosing an intermittent fault. Use the data captured when the DTC set, to determine if an open or shorted condition caused the DTC to set.

DTC P1650 - DRIVER 2 - INPUT VOLTAGE HIGH

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM contains Output Driver Modules (ODMs) that provides 7 switchable ground outputs for operating solenoids, relays, indicator lights, and other devices. Each of these ground outputs has fault lines that feed back to the PCM's microprocessor. ODM No. 2 can also sense high voltage coming in which might damage the microprocessor. DTC P1650 is used to monitor ODM No. 2 overvoltage sense line.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Start and idle engine. Using scan tool, select ENGINE 1 mode and note IGNITION 1 display. Compare this voltage reading with voltage reading displayed by vehicle message center. If PCM and vehicle voltage readings differ by greater than .5 volt, go to next step. If PCM and vehicle voltage readings are within .5 volt of each other, fault is not present. See DIAGNOSTIC AIDS.
3. Using DVOM, check voltage between ground and PCM fuse. If PCM fuse voltage and scan tool displayed voltage reading difference is greater than .5 volt, go to next step. If PCM fuse voltage and scan tool displayed voltage reading are within .5 volt of each other, check charging system. See the GENERATORS article in the ELECTRICAL section.
4. Check for high resistance in ignition feed circuits to PCM. Repair as necessary. If circuits are okay, go to next step.
5. Check terminal contacts at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
6. Replace PCM. Program replacement PCM using required equipment.

An overvoltage at ODM No. 2 will also trigger DTC P0563. Use DTC P0563 to diagnose if vehicle voltage is actually too high. A loose or faulty connection at generator "L" terminal may cause DTC P1650 to set intermittently.

DTC P1652 - LIFT/DIVE OUTPUT CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM contains chips called Output Driver Modules (ODM) that provide 7 switchable ground outputs for operating solenoids, relays, warming lights, and other devices. Each of these ground outputs has an internal fault line that feeds back to the PCM. When output is off, the output driver should receive 12 volts, fed to the solenoid driver, etc. When output is on, it should receive zero volts, since it is grounding the output. If it receives zero volts when output is off or 12 volts when output is on, it sets the fault line low.

DTC P1652 is used to monitor the fault line of the lift/dive output to the Road Sensing Suspension (RSS) module. The RSS module sends a 12 volt signal to the PCM connector C1 terminal No. 24. The PCM then grounds this circuit when vehicle is accelerating rapidly (lift) or braking hard (dive). The RSS module will then command the suspension to "firm", increasing controllability of vehicle during these conditions.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check PCM ride control output signal display. If display indicates OK, go to next step. If not, go to step 5).
3. Start and operate engine at idle. Using scan tool, command ride control to "firm". If display indicates OK, fault is not present. See DIAGNOSTIC AIDS. If not, go to next step.
4. Turn ignition off. Disconnect RSS module harness connector. Turn ignition on. Using DVOM, check voltage between ground and RSS module connector terminal A7. If voltage reading is 0.5 volts or greater, go to step 8). If not, go to step 12).
5. Store fluid life index. Turn ignition off. Wait 30 seconds, then disconnect PCM harness connector C1. Turn ignition on. Check voltage between ground and PCM harness connector C1 terminal No. 24. If voltage reading is 10 volts or greater, go to step 12). If not, go to next step.
6. Turn ignition off. Disconnect RSS harness connector. Check resistance between ground and RSS module harness connector terminal A7. If resistance is 10,000 ohms or less, go to step 9). If not, go to next step.
7. Check resistance between PCM harness connector C1 terminal No. 24 and RSS module harness connector terminal A7. If resistance is 5 ohms or less, go to step 11). If not, go to step 10).
8. Repair short to voltage on circuit No. 1490.
9. Repair short to ground on circuit No. 1490.
10. Repair open in circuit No. 1490.
11. Check terminal contact at RSS module. Repair as necessary. If repair is not required, diagnose RSS system.
12. Check terminal contact at PCM harness connector C1 terminal No. 24. Repair as necessary. If repair is not required, go to next step.
13. Replace PCM. Program replacement PCM using required equipment.

Use Failure Records to aid in diagnosing an intermittent fault. Use the data captured when the was DTC set, to determine is an open or shorted condition caused the DTC to set.

DTC P1654 - CRUISE DISABLE OUTPUT CIRCUIT

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM contains Output Driver Modules (ODM) that provides 7 switchable ground outputs for operating solenoids, relays, indicator lights, and other devices. Each of these ground outputs has fault lines that feed back to the PCM's microprocessor. When the output is off, the output driver should receive the 12 volts fed to the solenoid, relay, etc. When the output is on, it should receive zero volts, since it is grounding the output. when PCM sees zero volts when the output is off or 12 volts when the output is on, it sets a fault line low.

DTC P1645 is used to monitor the fault line of cruise disable output to the cruise control module. The cruise control module sends ignition voltage on the cruise inhibit output circuit to the PCM. The PCM will then ground this circuit to disengage cruise control module, if engaged or inhibit cruise control operation, if requested.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select ENGINE 3 mode and note CRUISE ENABLE DRIVER display. If scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 6).
3. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Turn ignition on. Using DVOM, check voltage between ground and cruise inhibit output circuit at PCM harness connector C1. If voltage reading is 10 volts or greater, fault is not present. See DIAGNOSTIC AIDS. If not, go to next step.
4. Turn ignition off. Disconnect cruise control module harness connector. Check resistance between ground and cruise control module harness connector terminal "H". If resistance is 5 ohms or less, go to step 8). If not, go to step 9).
5. Check resistance of cruise inhibit output circuit between cruise control module harness connector and PCM harness connector terminals. If resistance is 5 ohms or less, go to step 7). If not, go to step 9).
6. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Disconnect cruise control module. Turn ignition on. Using DVOM, check voltage between ground and cruise inhibit output circuit at PCM harness connector C1 terminal. If voltage reading is 10 volts or greater, go to step 10). If not, go to step 14).
7. Turn ignition on. Check voltage to ground at cruise control module terminal "F". If voltage reading is 10 volts or greater, go to step 12). If not, go to step 11).
8. Repair short to ground in cruise inhibit output circuit.
9. Repair open in cruise inhibit output circuit.
10. Repair short to voltage in cruise inhibit output circuit.
11. Repair open or short to ground (if fuse is blown) in ignition circuit to TCC brake switch and to cruise control module.
12. Check terminal contact at cruise control module. Repair as necessary. If terminal contact is okay, go to next step.
13. Replace cruise control module.
14. Check terminal contact at PCM. Repair as necessary. If terminal contact is okay, go to next step.
15. Replace PCM. Program replacement PCM using required equipment. Go to next step.

Use the FAILURE REC. to aid in diagnosing an intermittent fault. Use the data captured when the DTC set to determine if an open or shorted condition caused the DTC to set.

DTC P1660 - COOLING FAN CONTROL CIRCUITS

Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .

PCM Quad Driver Module (QDM) provides 4 switchable ground outputs for operating solenoids, relays, warning lights, and other devices. Each of these ground outputs has an internal fault line that feed back to the PCM. When the output is off, the quad driver should receive 12 volts fed to the solenoids, relays, etc. When the output is on, it should receive zero volts, since it is grounding the output. If it receives zero volts when the output is off or 12 volts when the output is on, it sets the fault line low. DTC is used to monitor the fault line of the cooling fan control relay output.

1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the «BASIC TESTING»(/cadillac/eldorado/x-1992-2002/remont/testing-diagnostics/#engine-controls-basic-engine-testing-46l) article. After performing OBD system check, go to next step.
2. Turn ignition on. Turn A/C controls off. Using scan tool in MISC TESTS select OUTPUT TESTS, then select FAN RELAYS. Note QUAD DRIVER 1 display and command ALL RELAYS off. If scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 8).
3. In MISC TESTS, select OUTPUT TESTS, then select FAN RELAYS. Note QUAD DRIVER 1 display and ALL RELAYS on. If scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 5).
4. If cooling fan is inoperative or if a fault is suspected, diagnose cooling fan. See the SYSTEM/COMPONENT TESTS article. If cooling fan operates, fault is not present.
5. While noting QUAD DRIVER 1 display, command FAN RELAY 1 on. If scan tool display indicates OK, go to step 7). If scan tool display does not indicate OK, go to next step.
6. Store fluid life index as indicated on scan tool. Turn ignition to LOCK position and wait 30 seconds, then disconnect PCM harness connector C2. Remove fan relay 1 (low speed). Using DVOM, check voltage between ground and cooling fan low speed control circuit at PCM harness connector terminal. If voltage reading is .5 volt or less, go to step 18). If not, go to step 16).
7. Store fluid life index as indicated on scan tool. Turn ignition switch to LOCK position and wait 30 seconds, then disconnect PCM harness connector C2. Remove fan relays 2 and 3. Using DVOM, check voltage between ground and cooling fan high speed control circuits at PCM harness connector. If voltage reading is .5 volt or less, go to step 18). If not, go to step 17).
8. With ALL RELAYS still commanded off, observe operation of both cooling fans. If either fan is operating, go to next step. If neither fan is operating, go to step 10).
9. Store fluid life index as indicated on scan tool. Turn ignition switch to LOCK position. Wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and cooling fan low speed control circuits at PCM harness connector. If voltage reading is less than 10 volts, go to step 15). If not, go to step 14).
10. Store fluid life index as indicated on scan tool. Turn ignition to LOCK position and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and cooling fan high and low speed control circuits at PCM harness connector. If voltage reading is 10 volts or greater, go to step 18). If not, go to next step.
11. If voltage reading from step 9) is low for both terminals, go to step 13). If voltage reading from step 9) is low only in one of the terminals, go to next step.
12. Repair open in circuit or replace fan relay for the circuit that measured low.
13. Repair cause of no voltage to both circuits. Replace fuse if blown.
14. Repair short to ground in cooling fan high speed control circuit.
15. Repair short to ground in cooling fan low speed control circuit.
16. Repair short to voltage in cooling fan low speed control circuit.
17. Repair short to voltage in cooling fan high speed control circuit.
18. Check terminal contact at PCM. Repair as necessary. If terminal contact is okay, go to next step.
19. Replace PCM. Program replacement PCM using required equipment.

See also:
• BASIC TESTING
• CONNECTOR IDENTIFICATION -- DEVILLE, ELDORADO & SEVILLE
• DIAGNOSTIC PROCEDURE
• HARD OR INTERMITTENT TROUBLE CODE DETERMINATION
• P0101
• P0102
• P0103
• P0105
• P0107
• P0108
• P0111
• P0112
• P0113
• P0116
• P0117
• P0118
• P0120
• P0121
• P0122
• P0123
• P0125
• P0131
• P0132
• P0133
• P0134
• P0135
• P0137
• P0138
• P0139
• P0140
• P0141
• P0143
• P0144
• P0146
• P0147
• P0151
• P0152
• P0153
• P0154
• P0155
• P0171
• P0172
• P0174
• P0175
• P0201
• P0202
• P0203
• P0204
• P0205
• P0206
• P0207
• P0208
• P0231
• P0232
• P0300
• P0322
• P0325
• P0326
• P0327
• P0340
• P0371
• P0372
• P0401
• P0404
• P0405
• P0420
• P0441
• P0506
• P0507
• P0550
• P0560
• P0563
• P1106
• P1107
• P1108
• P1111
• P1112
• P1114
• P1115
• P1121
• P1122
• P1133
• P1134
• P1139
• P1153
• P1154
• P1258
• P1320
• P1323
• P1350
• P1370
• P1371
• P1375
• P1376
• P1377
• P1380
• P1381
• P1404
• P1441
• P1508
• P1509
• P1524
• P1527
• P1554
• P1560
• P1564
• P1566
• P1570
• P1571
• P1574
• P1575
• P1576
• P1577
• P1578
• P1579
• P1599
• P1602
• P1603
• P1604
• P1605
• P1610
• P1611
• P1626
• P1630
• P1631
• P1632
• P1633
• P1634
• P1640
• P1641
• P1642
• P1644
• P1645
• P1650
• P1652
• P1654
• P1660
• CLEARING DIAGNOSTIC TROUBLE CODES (DTC)
• SCAN DATA
• CONNECTOR IDENTIFICATION
• DTC P0106