Engine Control System - Tests W/codes — Cadillac Catera I (1996-2001)

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 basic diagnostic procedures in the BASIC TESTING article. Failure to do so may result in lost diagnostic time.

If no faults were found while performing basic diagnostic procedures, proceed with DIAGNOSTIC PROCEDURE under SELF-DIAGNOSTIC SYSTEM. If no fault codes are present and driveability problems exist, proceed to 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 TESTS W/O CODES article.

DIAGNOSTIC SYSTEM

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

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

Passed the last test.
Ran and passed during this ignition cycle.
Ran and passed since DTCs were last cleared.
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.

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

Ensure all engine systems not related to computer system are operating properly. DO NOT proceed with testing unless all other problems have been repaired. Powertrain On-Board Diagnostic (OBD) System Check must be performed before using specific DTC testing procedure. See «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) .
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/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__hard-or-intermittent-trouble-code-determination) . For diagnosing hard codes, proceed to appropriate DTC test. For diagnosing intermittent codes, proceed to INTERMITTENTS in TESTS W/O CODES article.
If no DTCs are present and a driveability problem exists, refer to SYMPTOMS in TESTS W/O CODES article. Doing so will help identify proper system or component to check in SYSTEM/COMPONENT TESTS article.
After necessary repairs are made, clear DTCs, verify vehicle will enter "closed loop" operation and ensure DTC does not reset.

POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK

Note. Tech 1 or 2 scan tool is required to perform OBD system check.

The OBD System Check determines

If Malfunction Indicator Light (MIL) operates.
If PCM is operating and can recognize a fault.
If any DTCs are stored.

After performing procedures in PRELIMINARY INSPECTION & ADJUSTMENTS, BASIC FUEL SYSTEM CHECKS and BASIC IGNITION SYSTEM CHECKS in BASIC TESTING article, this is the starting point for utilizing the self-diagnostic system for determining computer-related problems. After performing necessary tests as described in the diagnostic circuit check, if no codes are indicated and driveability problems still exist, see TESTS W/O CODES article and SCAN TOOL USAGE.

Check if Malfunction Indicator Light (MIL) is illuminated with engine running. Check for driveability concerns. Also, check for faulty computer-controlled components. If problem is found, go to next step.
Turn ignition off. Install scan tool and follow scan tool manufacturer's instructions to proceed with test. Turn ignition on. If scan tool displays PCM data, go to next step. If scan tool does not display PCM data, go to DLC DIAGNOSIS or NO SCAN TOOL DATA.
Crank engine. If engine cranks, go to next step. If engine does not crank, diagnose starting and charging system.
Turn ignition on with engine off. Observe Malfunction Indicator Light (MIL). If MIL illuminates, go to next step. If MIL does not illuminate, go to MIL DIAGNOSIS.
Attempt to start engine. If engine starts and runs, go to next step. If engine does not start, or starts and dies, go to NO START DIAGNOSIS in BASIC TESTING article.
Check for any applicable technical service bulletins. Perform repairs as necessary. If no applicable bulletins are found, go to next step.
Using scan tool, check for Diagnostic Trouble Codes (DTCs). If DTCs are not present, go to step 9). If any DTCs are present, go to next step.
Using scan tool, store FREEZE FRAME data. Diagnose any stored DTC.
Start engine. Observe Malfunction Indicator Light (MIL) with engine running. If MIL illuminates, go to MIL DIAGNOSIS. If MIL does not illuminate, go to next step.
Compare scan tool engine data with actual control system data values. If value is within limits, see TESTS W/O CODES article. If value is not within limits, go to SYSTEM/COMPONENT TESTS article.

MIL DIAGNOSIS

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition on with engine off. If Malfunction Indicator Light (MIL) illuminates, go to step 7). If MIL does not illuminate, go to next step.
Disconnect IAC motor connector. Using a test light connected to ground, probe IAC motor connector switched battery voltage circuit. If test light illuminates, go to next step. If test light does not illuminate, diagnose main relay circuit.
Check instrument cluster ignition feed circuit fuse. If fuse is blown, go to step 10). If fuse is okay, go to next step.
Turn ignition off. Disconnect ECM connector. Turn ignition on. Using a fused jumper wire, jumper MIL control circuit at ECM connector to ground. See WIRING DIAGRAMS article. If MIL illuminates, go to step 11). If MIL does not illuminate, go to next step.
Check for faulty bulb, open in ignition feed to bulb, or open or short to voltage in control circuit. Repair as necessary. After repairs, go to step 13).
Using scan tool, check if any DTCs are present. If DTCs are present, perform OBD system check. If DTCs are not present, go to next step.
Turn ignition off. Disconnect ECM connector. Turn ignition on with engine off. If MIL illuminates, go to next step. If MIL does not illuminate, go to step 12).
Repair short to ground in MIL control circuit. Repair as necessary. After repairs, go to step 13).
Repair short to ground in instrument cluster ignition feed circuit. Repair as necessary. After repairs, go to step 13).
Check for poor ECM connections. Repair as necessary. After repairs, go to step 13). If connections are okay, go to next step.
Replace ECM. Perform ECM relearn procedures. After repairs, go to next step.
Start engine and observe MIL. MIL should momentarily illuminate, then go out. If MIL illuminates as specified, system is okay. If MIL does not illuminate as specified, perform OBD system check.

DLC DIAGNOSIS OR NO SCAN TOOL DATA

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition on with engine off. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, go to step 9).
If engine starts and continues to run, go to step 12). If engine does not start, or starts and then dies, go to next step.
Turn ignition off. Disconnect ECM connector. Using a test light connected to ground, probe ECM ignition feed circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 6).
Using a test light connected to battery voltage, probe ECM ground circuits. See WIRING DIAGRAMS article. If test light illuminates on all ground circuits, go to step 16). If test light does not illuminate on all ground circuits, go to step 7).
Repair ignition feed circuit. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) .
Repair open or high resistance in affected circuit. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) .
Repair short to ground in affected circuit. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) .
Disconnect scan tool. Using a test light connected to ground, probe DLC battery feed circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 11).
Using a test light connected to battery voltage, probe DLC ground circuits. See WIRING DIAGRAMS article. If test light illuminates for both ground circuits, go to step 18). If test light does not illuminate for both ground circuits, go to step 14).
Repair DLC battery feed circuit. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) .
Disconnect scan tool. Using a test light connected to battery voltage, probe DLC ground circuits. See WIRING DIAGRAMS article. If test light illuminates for both ground circuits, go to next step. If test light does not illuminate for both ground circuits, go to step 14).
Check for open, short to ground or short to voltage in serial data circuit. Repair as necessary. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) . If circuit is okay, go to step 15).
Repair open or high resistance in DLC ground circuits. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) .
Install scan tool on another vehicle and check for proper operation. If scan tool operates properly, go to next step. If scan tool does not operate properly, go to step 18).
Check ECM for proper terminal tension or poor connection. Repair as necessary. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) . If terminals and connection are okay, go to next step.
Replace ECM. Perform ECM relearn procedures. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) .
Replace faulty scan tool. After scan tool replacement, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) .

READING TROUBLE CODES

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

TROUBLE CODE DEFINITION

Code No.	Circuit Affected
P0100	MAF Sensor Circuit
P0101	MAF System Performance
P0110	IAT Sensor Circuit
P0115	ECT Sensor Circuit
P0116	ECT Sensor Circuit Performance
P0120	TP Sensor Circuit
P0130	HO2S Circuit Bank 1, Sensor 1
P0131	HO2S Circuit Low Voltage-Bank 1, Sensor 1
P0132	HO2S Circuit High Voltage-Bank 1, Sensor 1
P0133	HO2S Slow Response-Bank 1, Sensor 1
P0134	HO2S Insufficient Activity-Sensor 1
P0135	HO2S Heater Circuit-Bank 1, Sensor 1
P0136	HO2S Circuit-Bank 1, Sensor 2
P0137	HO2S Circuit Low Voltage-Bank 1, Sensor 2
P0138	HO2S Circuit High Voltage-Bank 1, Sensor 2
P0140	HO2S Insufficient Activity-Bank 1, Sensor 2
P0141	HO2S Heater Circuit-Bank 1, Sensor 2
P0150	HO2S Circuit-Bank 2, Sensor 1
P0151	HO2S Circuit Voltage Low-Bank 2, Sensor 1
P0152	HO2S Circuit Voltage High-Bank 2, Sensor 1
P0153	HO2S Slow Response-Bank 2, Sensor 1
P0155	HO2S Heater Circuit-Bank 2, Sensor 1
P0156	HO2S Circuit-Bank 2, Sensor 2
P0157	HO2S Circuit Voltage Low-Bank 2, Sensor 2
P0158	HO2S Circuit Voltage High-Bank 2, Sensor 2
P0160	HO2S Insufficient Activity-Bank 2, Sensor 2
P0161	HO2S Heater Circuit-Bank 2, Sensor 2
P0171	Fuel Trim System Lean-Bank 1
P0172	Fuel Trim System Rich-Bank 1
P0174	Fuel Trim System Lean-Bank 2
P0175	Fuel Trim System Rich-Bank 2
P0201	Injector No. 1 Control Circuit
P0202	Injector No. 2 Control Circuit
P0203	Injector No. 3 Control Circuit
P0204	Injector No. 4 Control Circuit
P0205	Injector No. 5 Control Circuit
P0206	Injector No. 6 Control Circuit
P0230	Fuel Pump Control Circuit
P0300	Engine Misfire Detected
P0301	Cyl. No. 1 Misfire Detected
P0302	Cyl. No. 2 Misfire Detected
P0303	Cyl. No. 3 Misfire Detected
P0304	Cyl. No. 4 Misfire Detected
P0305	Cyl. No. 5 Misfire Detected
P0306	Cyl. No. 6 Misfire Detected
P0325	Knock Sensor Circuit-Bank 1
P0330	Knock Sensor Circuit-Bank 2
P0335	CKP Sensor Circuit
P0336	CKP Sensor System Performance
P0340	Camshaft Position Sensor Circuit
P0410	AIR Constant Flow Detected
P0411	AIR System No Flow Detected
P0412	AIR Solenoid Valve Control Circuit
P0422 /P0432	TWC System Low Efficiency-Bank 1 & 2
P0440	EVAP System
P0441	EVAP System Incorrect Purge Flow
P0443	EVAP Purge Valve Control
P0446	EVAP Vent Valve Control
P0450	EVAP Fuel Tank Pressure Sensor Circuit
P0455	EVAP System Large Leak Detected
P0501	Vehicle Speed Signal Circuit
P0506	Idle Speed Low-IAC Responding
P0507	Idle System High-IAC Responding
P0560	System Voltage
P0601	ECM Memory
P0602	ECM Not Programmed
P0604	ECM RAM
P1112	Intake Plenum Switchover Valve Control
P1113	Intake Resonance Switchover Valve Control
P1460	Misfire Detected With Low Fuel
P1501	Theft Deterrent System
P1502	Theft Deterrent System-No Password Received
P1503	Theft Deterrent System-Password Incorrect
P1564	ECM Battery Voltage Loss
P1601	ECM Overtemperature
P1602	Knock Sensor Module Circuit
P1700	MIL Requested By TCM
P1701	MIL Request Circuit
P1740	Torque Management Request Circuits

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

Enter diagnostic mode. Read and record all stored DTCs. Exit diagnostic mode, and clear DTCs. See «CLEARING DIAGNOSTIC TROUBLE CODES (DTC)»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__clearing-diagnostic-trouble-codes-dtc) .
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.
If MIL illuminates, enter diagnostic mode. Read and record DTCs. This will reveal hard failure codes. Oxygen sensor related DTCs may require a road test to reset hard failure after DTCs were cleared.
If MIL does not illuminate, all stored DTCs were intermittent failures.

Note. DTCs will be recorded at various operating times. Some DTCs 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 a more precise location, see COMPONENT LOCATIONS in 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. For scan data values, refer to scan tool manufacturer owner's manual or compare values with a known-good component or vehicle.

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. See POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. 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. 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 ECM/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 setting 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.

SUMMARY

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

DIAGNOSTIC TROUBLE CODES

Note. Before clearing DTCs, perform procedures under POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . Record FREEZE FRAME and FAILURE RECORDS for reference during testing. Data will be erased when DTCs are cleared. If ECM/PCM/VCM is replaced, NEW ECM/PCM/VCM must be programmed using special manufacturer's equipment.

DTC P0100 - MAF SENSOR CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

Circuit Description

Mass Airflow (MAF) sensor measures airflow rate into engine. MAF sensor has a switched battery feed, signal circuit, signal return circuit and a ground. As airflow increases, a greater amount of current is required to maintain the hot wires at a constant temperature. MAF sensor converts the changes in current draw to a frequency signal read by the ECM. ECM calculates airflow (grams per second) based on this signal.

ECM monitors the MAF sensor frequency and can determine if sensor is stuck low, stuck high, not providing the airflow value expected for a given operating condition, or not providing signal variation expected during normal operation. If MAF sensor frequency varies less than a predetermined minimum amount, this DTC will set.

Conditions required to set DTC are

Engine speed greater than 400 RPM or when cranking, engine speed is greater than 120 RPM.
MAF signal indicates an airflow of less than 1.38 grams per seconds (gm/s) or exceeds the maximum value for a given RPM. See «MAF SPECIFICATIONS»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes) table.
Conditions must be present for at least 0.1 second.

Engine RPM	Max. Grams Per Second
1000	84
2000	111
3000	140
4000	180
5000	222
6000	251

MAF SPECIFICATIONS

Diagnostic Procedures

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition on, with engine off. Using scan tool, read MAF sensor voltage. If voltage is greater than 4.8 volts, go to step 7). If voltage is less than 4.8 volts, go to next step.
Start and idle engine. With engine idling, monitor MAF sensor voltage on scan tool. If MAF sensor voltage is less than 0.2 volt, go to step 12). If MAF sensor voltage is greater than 0.2 volt, go to next step.
Check for air leaks between MAF sensor and throttle body. Repair as necessary. After repairs, go to step 27). If problem is not found, go to next step.
Move/wiggle harness and related connectors while monitoring MAF sensor voltage on scan tool. If movement changes MAF sensor voltage, go to step 16). If movement does not change MAF sensor voltage, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start and operate engine at greater than 400 RPM, as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0100 is set, go to step 23). If DTC P0100 is not set, see DIAGNOSTIC AIDS.
Disconnect MAF sensor connector. If scan tool displays zero voltage, go to next step. If scan tool does not display zero voltage, go to step 11).
Using test light connected to battery voltage, probe ground circuit at MAF sensor harness connector. If test light illuminates, go to next step. If test light does not illuminates, go to step 17).
With test light still connected to battery voltage, probe signal return circuit at MAF sensor harness connector. If test light illuminates, go to step 24). If test light does not illuminate, go to next step.
Turn ignition off. Disconnect ECM harness connector. ECM is located in engine compartment relay center. Using DVOM, check continuity of MAF sensor signal return circuit between ECM and MAF sensor harness connectors. If continuity is present, go to step 25). If continuity is not present, go to step 18).
Turn ignition off. Disconnect ECM harness connector. ECM is located in engine compartment relay center. Turn ignition on, with engine off. Using DVOM, check voltage of signal circuit at MAF sensor harness connector. If voltage is present, go to step 19). If voltage is not present, go to step 26).
Disconnect MAF sensor. Using test light connected to battery voltage, probe MAF sensor signal circuit at MAF sensor harness connector. If scan tool displays 5 volts, go to next step. If scan tool does not display 5 volts, go to step 14).
Using test light connected to ground, probe MAF sensor battery feed circuit at MAF sensor harness connector. If test light illuminates, go to step 23). If test light does not illuminate, go to step 20).
Turn ignition off. Disconnect ECM harness connector. Using DVOM, check continuity of MAF sensor signal circuit between ECM and MAF sensor harness connectors. If continuity is not present, go to step 21). If continuity is present, go to next step.
Using DVOM, check for continuity between MAF sensor signal circuit and ground. If continuity is present, go to step 22). If continuity is not present, go to step 25).
Repair harness or connections as necessary. After repairs, go to step 27).
Repair open or high resistance in ground circuit. After repairs, go to step 27).
Repair open or high resistance in signal return circuit. After repairs, go to step 27).
Repair short to voltage in signal circuit. After repairs, go to step 27).
Repair open or high resistance in switched battery feed circuit. After repairs, go to step 27).
Repair open or high resistance in signal circuit. After repairs, go to step 27).
Repair short to ground in signal circuit. After repairs, go to step 27).
Check for poor connections and terminal tension at MAF sensor harness connector. Repair as necessary. After repairs, go to step 27). If connections and terminals are okay, go to next step.
Replace MAF sensor. After replacing sensor, go to step 27).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 27). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate engine at greater than 400 RPM. Check for DTCs. If DTC P0100 is set, go to step 2). If DTC P0100 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for poor connections at ECM or at component. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connection.

Check for misrouted wiring harness. Inspect harness to ensure that it is not routed too close to high voltage wires (spark plug wires) or too close to high current devices (generator, motors, solenoids).

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault. If sensor signal is only affected when harness is moved at a component, and there is no problem with wiring harness or connections, component may be faulty.

Check for plugged intake air duct or dirty air filter.

DTC P0101 - MAF SENSOR SYSTEM PERFORMANCE

Note. For circuit reference, see WIRING DIAGRAMS article.

ECM monitors the MAF sensor frequency and can determine if sensor is stuck low, stuck high, not providing the airflow value expected for a given operating condition, or not providing the signal variation expected during normal operation. If MAF sensor frequency varies less than a predetermined minimum amount, this DTC will set.

TP sensor load signal is 2.0-3.3 milliseconds.
Condition is met for at least 7 seconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
If DTC P0120 or P0121 is also set, diagnose affected DTC first. If DTC P0120 or P0121 is not set, go to next step.
Check if DTC P0100 is also set, go to that DTC. If DTC P0100 is not set, go to next step.
Start engine and accelerate to Wide Open Throttle (WOT). Using scan tool, observe TP and MAF sensor signals. If both parameters increase in value as WOT is performed, go to step 6). If both parameters do not increase in value as WOT is performed, go to next step.
If MAF sensor signal did not increase in value during WOT, go to step 7). If TP signal did not increase in value during WOT, go to DTC P0120 (TP SENSOR CIRCUIT).
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start and operate engine at speed greater than 520 RPM at normal operating temperature, and as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0100 is set, go to step 23). If DTC P0100 is not set, see DIAGNOSTIC AIDS.
Check for objects blocking MAF sensor inlet screen. Check for intake manifold and throttle body vacuum leaks or air leaks in intake duct system between MAF and throttle body. Check PCV system operation. Check for loose or missing oil fill cap or unseated engine oil dipstick. Repair as necessary. After repairs, go to step 27). If no problems are found, go to next step.
Turn ignition on, with engine off. Disconnect MAF sensor connector. If scan tool displays zero volts, go to next step. If scan tool does not display zero volts, go to step 12).
Using test light connected to battery voltage, probe ground circuit at MAF sensor harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 18).
With test light still connected to battery voltage, probe signal return circuit at MAF sensor harness connector. If test light is illuminated, go to step 25). If test light does not illuminate, go to next step.
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using a DVOM, check continuity of MAF sensor signal return circuit between ECM and MAF sensor harness connectors. If continuity is present, go to step 26). If continuity is not present, go to step 19).
Turn ignition off. Disconnect ECM harness connector. Turn ignition on, with engine off. Using DVOM, check voltage of signal circuit at MAF sensor harness connector. If voltage is present, go to step 20). If voltage is not present, go to step 27).
Disconnect MAF harness sensor. Using test light connected to battery voltage, probe MAF sensor signal circuit at MAF sensor harness connector. If scan tool displays 5 volts, go to next step. If scan tool does not display 5 volts, go to step 15).
Using test light connected to ground, probe MAF sensor battery feed supply circuit at MAF sensor harness connector. If test light illuminates, go to step 24). If test light does not illuminate, go to step 21).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check continuity of MAF sensor signal circuit between ECM and MAF sensor harness connectors. If continuity is not present, go to step 22). If continuity is present, go to next step.
Using DVOM, check for continuity between MAF sensor signal circuit and ground. If continuity is present, go to step 23). If continuity is not present, go to step 26).
Repair harness connector or terminal connections as necessary. After repairs, go to step 28).
Repair open or high resistance in ground circuit, then go to step 28).
Repair open or high resistance in signal return circuit. After repairs, go to step 28).
Repair short to voltage in signal circuit. After repairs, go to step 28).
Repair open or high resistance in switched battery feed circuit. After repairs, go to step 28).
Repair open or high resistance in signal circuit. After repairs, go to step 28).
Repair short to ground in signal circuit. After repairs, go to step 28).
Check for poor connections and terminal tension at MAF sensor harness connector. Repair as necessary. After repairs, go to step 28). If connections and terminals are okay, go to next step.
Replace MAF sensor. After replacing sensor, go to step 28).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 28). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start and operate engine at speed greater than 520 RPM at normal operating temperature. Check for DTCs. If DTC P0101 is set, go to step 2). If DTC P0101 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for skewed or stuck TP sensor. A faulty TP sensor or TP sensor circuit can cause ECM to incorrectly calculate predicted mass airflow value. Observe throttle angle with throttle closed. If throttle angle reading is not within typical scan tool values, check for the following conditions

Check for sticking throttle plate or excessive deposits on throttle plate or throttle bore, TP sensor signal circuit for short to voltage or for poor connection or high resistance in TP sensor ground circuit.

Check for plugged intake air duct or dirty air filter. A wide open throttle acceleration from a stop should cause mass airflow displayed on scan tool to increase from about 4-7 gm/s at idle to 100 gm/s or more at the time of 1-2 shift. If increase is not as specified, check for a restriction.

Check for water entering air intake system and contaminating MAF sensor. Water rapidly cools hot wires in sensor, causing a false indication of excessive airflow. Check air filter housing for evidence of water.

DTC P0110 - IAT SENSOR CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

Intake Air Temperature (IAT) sensor contains a thermistor which changes resistance based on temperature. IAT sensor is located in air intake passage. Sensor has a signal and ground circuit. ECM applies about 5 volts on sensor signal circuit. ECM monitors changes in voltage caused by changes in resistance of sensor to determine intake air temperature.

When intake air is cold, sensor resistance is high. ECM will sense a high signal voltage (low temperature). When intake air is warm, sensor resistance is low. ECM will sense a low signal voltage (high temperature). When ECM senses a signal voltage outside normal operating range of sensor, this DTC will set.

Conditions required to set DTC are

IAT signal voltage indicates an intake air temperature greater than 282°F (139°C) or less than -45°F (-43°C).
Conditions are met for at least 10 seconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition on, with engine off. Using scan tool, monitor IAT sensor temperature. If IAT sensor temperature is greater than 282°F (139°C), go to step 6). If IAT sensor temperature is less than 282°F (139°C), go to next step.
If IAT sensor temperature is less than -45°F (-43°C), go to step 8). If IAT sensor temperature is greater than -45°F (-43°C), go to next step.
Turn ignition on, with engine off. Move IAT sensor and ECM wiring harness and connectors while observing scan tool display. If IAT sensor value on scan tool display changes when moving wiring harness or connectors, go to step 12). If IAT sensor value on scan tool display does not change when moving wiring harness or connectors, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate for at least 3 minutes, as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0110 is set, go to next step. If DTC P0110 is not set, see DIAGNOSTIC AIDS.
Disconnect IAT sensor harness connector. Observe scan tool display. If IAT sensor temperature is less than -45°F (-43°C), go to step 17). If IAT sensor temperature is greater than -45°F (-43°C), go to next step.
Turn ignition off. Disconnect ECM harness connector, located in engine compartment relay center. Using DVOM, check continuity between IAT sensor signal circuit and ground. If continuity is present, go to step 13). If continuity is not present, go to step 19).
Disconnect IAT sensor connector. Jumper IAT sensor harness connector terminals together. Observe scan tool display. If IAT sensor temperature is greater than 282°F (139°C), go to step 16). If IAT sensor temperature is less than 282°F (139°C), go to next step.
Jumper IAT sensor signal circuit to a known good ground. Observe scan tool display. If IAT sensor temperature is greater than 282°F (139°C), go to step 11). If IAT sensor temperature is less than 282°F (139°C), go to next step.
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check continuity of sensor signal circuit between ECM and IAT sensor harness connectors. If continuity is present, go to step 18). If continuity is not present, go to step 14).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check continuity of sensor ground circuit between ECM and IAT sensor harness connectors. If continuity is present, go to step 18). If continuity is not present, go to step 15).
Repair harness or connections as necessary. After repairs, go to step 20).
Repair short to ground in signal circuit. After repairs, go to step 20).
Repair open or high resistance in signal circuit. After repairs, go to step 20).
Repair open or high resistance in ground circuit. After repairs, go to step 20).
Check for poor connections and terminal tension at IAT sensor harness connector. Repair as necessary. After repairs, go to step 20). If connections and terminals are okay, go to next step.
Replace IAT sensor. After replacing sensor, go to step 20).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 20). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate at least 3 minutes, and as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0110 is set, go to step 2). If DTC P0110 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

If other DTCs are set that share the same ground circuit, check point where circuits ground to chassis or engine block. If engine has been allowed to sit over night, engine coolant temperature and engine intake air temperature values should display within a few degrees of each other. If temperatures are not within 5°F (3°C), refer to IAT TEMPERATURE VS. RESISTANCE table.

When checking IAT sensor, refer to IAT TEMPERATURE VS. RESISTANCE table to test sensor at various temperature levels to check for shifted sensor. A shifted sensor could result in poor driveability complaints.

Temperature °F (°C)	Ohms
210 (99)	200
160 (71)	450
100 (38)	1300
70 (21)	2500
40 (4)	5200
20 (-7)	8250
0 (-18)	14800

IAT TEMPERATURE VS. RESISTANCE

IAT TEMPERATURE-TO-RESISTANCE VALUES

Temperature °F (°C)	Ohms
212 (100)	177
194 (90)	241
158 (70)	467
122 (50)	973
104 (40)	1459
86 (30)	2238
68 (20)	3520
50 (10)	5670

IAT TEMPERATURE-TO-RESISTANCE VALUES

DTC P0115 - ECT SENSOR CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

Engine Coolant Temperature (ECT) sensor contains a thermistor which changes resistance based on temperature. ECT sensor is located in coolant crossover pipe at center rear of engine. Sensor has a signal and ground circuit. ECM applies about 5 volts on signal circuit of sensor. ECM monitors changes in voltage caused by changes in resistance of sensor to determine engine coolant temperature.

When engine coolant is cold, sensor resistance is high. ECM will sense a high signal voltage (low temperature). When engine coolant is warm, sensor resistance is low. ECM will sense a low signal voltage (high temperature). When ECM senses a signal voltage outside normal operating range of sensor, this DTC will set.

Conditions required to set DTC are

ECT signal voltage indicates an intake air temperature greater than 282°F (139°C) or less than -45°F (-43°C).
Conditions are met for at least 2 seconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition on, with engine off. Using scan tool, monitor ECT sensor temperature. If ECT sensor temperature is greater than 282°F (139°C), go to step 6). If ECT sensor temperature is less than 282°F (139°C), go to next step.
If ECT sensor temperature is less than -45°F (-43°C), go to step 8). If ECT sensor temperature is greater than -45°F (-43°C), go to next step.
Turn ignition on, with engine off. Move/wiggle ECT sensor and ECM wiring harness and connectors while observing scan tool display. If ECT sensor value on scan tool display changes when moving wiring harness or connectors, go to step 12). If ECT sensor value on scan tool display does not change when moving wiring harness or connectors, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0115 is set, go to next step. If DTC P0115 is not set, see DIAGNOSTIC AIDS.
Disconnect ECT sensor connector. Observe scan tool display. If ECT sensor temperature is less than -45°F (-43°C), go to step 17). If ECT sensor temperature is greater than -45°F (-43°C), go to next step.
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check for continuity between ECT sensor signal circuit and ground. If continuity is not present, go to step 19). If continuity is present, go to step 13).
Disconnect ECT sensor connector. Jumper ECT sensor harness connector terminals together. Observe scan tool display. If ECT sensor temperature is greater than 282°F (139°C), go to step 16). If ECT sensor temperature is less than 282°F (139°C), go to next step.
Jumper ECT sensor signal circuit to a known good ground. Observe scan tool display. If ECT sensor temperature is greater than 282°F (139°C), go to step 11). If ECT sensor temperature is less than 282°F (139°C), go to next step.
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check continuity of sensor signal circuit between ECM and ECT sensor harness connectors. If continuity is present, go to step 18). If continuity is not present, go to step 14).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check continuity of sensor ground circuit between ECM and ECT sensor harness connectors. If continuity is present, go to step 18). If continuity is not present, go to step 15).
Repair harness or connections as necessary. After repairs, go to step 20).
Repair short to ground in signal circuit. After repairs, go to step 20).
Repair open or high resistance in signal circuit. After repairs, go to step 20).
Repair open or high resistance in ground circuit. After repairs, go to step 20).
Check for poor connections and terminal tension at ECT sensor harness connector. Repair as necessary. After repairs, go to step 20). If connections and terminals are okay, go to next step.
Replace ECT sensor. After replacing sensor, go to step 20).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 20). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0115 is set, go to step 2). If DTC P0115 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

When checking ECT sensor, refer to ECT TEMPERATURE VS. RESISTANCE table to test sensor at various temperature levels to check for shifted sensor. A shifted sensor could result in poor driveability complaints.

Temperature °F (°C)	Ohms
210 (99)	190
160 (71)	400
100 (38)	1250
70 (21)	2350
40 (4)	4780
20 (-7)	8100
0 (-18)	14650

ECT TEMPERATURE VS. RESISTANCE

DTC P0116 - ECT SENSOR CIRCUIT PERFORMANCE

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions required to set DTC are

Difference between calculated engine coolant temperature and actual engine coolant temp is greater than 11°F (20°C).

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Disconnect ECT sensor connector. Observe scan tool display. If ECT sensor temperature is less than -45°F (-43°C), go to next step. If ECT sensor temperature is greater than -45°F (-43°C), go to DTC P0110 (IAT SENSOR CIRCUIT).
Jumper ECT sensor harness connector terminals. Observe scan tool display. If ECT sensor temperature is greater than 282°F (139°C), go to next step. If ECT sensor temperature is less than 282°F (139°C), go to DTC P0110 (IAT SENSOR CIRCUIT).
Replace ECT sensor. After replacing sensor, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and let idle. Check for DTCs. If DTC P0116 is set, go to step 2). If DTC P0116 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

If other DTCs are set that share the same ground circuit, check point where circuits ground to chassis or engine block. If engine has been allowed to sit overnight, ECT and IAT values should be within a few degrees of each other. If temperatures are not within 5°F (3°C), refer to ECT TEMPERATURE VS. RESISTANCE table under DTC P0115.

When checking ECT sensor, refer to ECT TEMPERATURE VS. RESISTANCE table under DTC P0115 to test sensor at various temperature levels and to check for shifted sensor. A shifted sensor could result in poor driveability complaints.

Check for stuck open thermostat. A stuck thermostat during very cold temperatures will cause engine temperature to increase too slowly and could result in this DTC being set.

ECT TEMPERATURE-TO-RESISTANCE VALUES

Temperature °F (°C)	Ohms
212 (100)	177
194 (90)	241
158 (70)	467
122 (50)	973
104 (40)	1459
86 (30)	2238
68 (20)	3520
50 (10)	5670

ECT TEMPERATURE-TO-RESISTANCE VALUES

DTC P0120 - TP SENSOR CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

Throttle Position (TP) sensor is a potentiometer. Sensor is mounted on side of throttle body. Sensor provides a voltage signal that changes relative to throttle blade angle. This signal voltage is one of the most important used by ECM. Sensor has a signal circuit, ground circuit and a 5-volt reference circuit. Signal circuit is increased to 5 volts within ECM. When ECM senses a signal voltage outside normal operating range of sensor, this DTC will set.

Conditions required to set DTC are

Throttle angle is greater than 96 percent or less than 3.9 percent.
Condition is met for at least 50 milliseconds.
While cranking engine, previous conditions are met for at least 2 seconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition on, with engine off. Using scan tool, monitor TP sensor voltage. If TP sensor voltage is 0.3-0.9 volt, go to next step. If TP sensor voltage is not 0.3-0.9 volt, go to step 6).
Fully depress accelerator pedal. If TP sensor voltage is 3.3-3.9 volts, go to next step. If TP sensor voltage is not 3.3-3.9 volts, go to step 6).
Turn ignition on, with engine off. Move/wiggle TP sensor and ECM wiring harness and connectors while observing scan tool display. If TP sensor value on scan tool display changes when moving wiring harness or connectors, go to step 17). If TP sensor value on scan tool display does not change when moving wiring harness or connectors, go to next step.
Turn ignition off. Disconnect TP sensor connector. Using 2 jumper wires, reconnect TP sensor 5 volt reference circuit and ground circuit between wiring harness and TP sensor. Connect DVOM between ground and TP sensor signal circuit terminal at TP sensor. Slowly move throttle plate to Wide Open Throttle (WOT), then return it to closed throttle position while observing voltage display on DVOM. Voltage should increase smoothly to WOT position and decrease smoothly as throttle is slowly closed without any voltage spikes or drop outs noted on DVOM. If TP sensor voltage is as specified, go to step 26). If TP sensor voltage is not as specified, see DIAGNOSTIC AIDS.
Disconnect TP sensor connector. Using DVOM, check voltage between ground and signal circuit at TP sensor harness connector. If voltage is 4.7-5.3 volts, go to step 10). If voltage is not 4.7-5.3 volts, go to next step.
Turn ignition off. Leave TP sensor disconnected. Disconnect ECM harness connector. Turn ignition on. Using DVOM, check voltage between ground circuit and signal circuit at TP sensor harness connector. If any voltage is present, go to step 21). If no voltage is present, go to next step.
Using DVOM, check harness continuity of TP sensor signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 22).
Using DVOM, check harness continuity between TP sensor signal circuit and ground. If continuity is present, go to step 23). If continuity is not present, go to step 27).
Using DVOM, check voltage between ground and 5 volt reference circuit at TP sensor harness connector. If voltage is 4.7-5.3 volts, go to step 14). If voltage is not 4.7-5.3 volts, go to next step.
Turn ignition off. Leave TP sensor disconnected. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and 5 volt reference circuit at TP sensor harness connector. If any voltage is present, go to step 18). If no voltage is present, go to next step.
Using DVOM, check harness continuity of TP sensor 5 volt reference circuit. If continuity is present, go to next step. If continuity is not present, go to step 19).
Using DVOM, check harness continuity between TP sensor 5 volt reference circuit and ground. If continuity is present, go to step 20). If continuity is not present, go to step 27).
Turn ignition off. Using a test light connected to battery voltage, probe TP sensor harness connector ground circuit. If test light is illuminates, go to step 16). If test light does not illuminate, go to next step.
Leave TP sensor disconnected. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check harness continuity of TP sensor ground circuit. If continuity is present, go to step 27). If continuity is not present, go to step 24).
Turn ignition on, with engine off. Using scan tool, monitor TP sensor voltage. Using a fused jumper wire, jumper signal circuit to ground circuit at TP sensor harness connector. Observe scan tool display. If scan tool displays zero volts, go to step 25). If scan tool does not display zero volts, go to step 28) .
Repair harness or connections as necessary. After repairs, go to step 29).
Repair short to voltage in 5 volt reference circuit. After repairs, go to step 29).
Repair open or high resistance in 5 volt reference circuit. After repairs, go to step 29).
Repair short to ground in 5 volt reference circuit. After repairs, go to step 29).
Repair short to voltage in signal circuit. After repairs, go to step 29).
Repair open or high resistance in signal circuit. After repairs, go to step 29).
Repair short to ground in signal circuit. After repairs, go to step 29).
Repair open or high resistance in ground circuit. After repairs, go to step 29).
Check for poor connections and terminal tension at TP sensor harness connector. Repair as necessary. After repairs, go to step 29). If connections and terminals are okay, go to next step.
Replace TP sensor. After replacing sensor, go to step 29).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 29). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start and operate at greater than 400 RPM. Check for DTCs. If DTC P0120 is set, go to step 2). If DTC P0120 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

If other DTCs are set that share the same 5-volt reference circuit, check entire circuit up to any other components. Check for shorts to ground or power. If DTCs that are set share the same ground circuit, check point where circuits ground to chassis or engine block.

DTC P0130 - HO2S CIRCUIT BANK 1, SENSOR 1

Note. For circuit reference, see WIRING DIAGRAMS article.

Heated Oxygen Sensor (HO2S) produces a voltage that varies between -100 mV and 900 mV under normal operating conditions. Full operating range of HO2S circuit is about from -406 mV to 1124 mV. ECM monitors this voltage and determines if exhaust is lean or rich. Oxygen sensor voltage is high when exhaust is rich, and low when exhaust is lean. ECM constantly monitors HO2S signal during closed loop operation and compensates for rich or lean condition by decreasing or increasing injector pulse width as necessary. If ECM detects low HO2S voltage for an extended period of time, this DTC will set.

Conditions required to set DTC are

HO2S voltage is between 62 mV and 399 mV.
Condition is met for longer than 20 seconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and warm engine to normal operating temperature. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool remains less than 399 mV, go to step 4). If HO2S voltage value on scan tool does not remain less than 399 mV, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0130 is set, go to next step. If DTC P0130 is not set, see DIAGNOSTIC AIDS.
Turn ignition on, with engine off. Disconnect HO2S connector. Check for signs of water or corrosion. Repair as necessary. If HO2S voltage value on scan tool is 375-525 mV, go to step 14). If HO2S voltage value on scan tool is not 375-525 mV, go to next step.
Using DVOM, check voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 11).
Using DVOM, check voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to step 22). If voltage is not 700-800 mV, go to next step.
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect the 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting other sensors restores voltage to 700-800 mV, go to step 14). If disconnecting one of the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector. Turn ignition on. Using DVOM, check voltage between ground and HO2S low circuit at ECM harness connector. If any voltage is present, go to step 15). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 16).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 17). If continuity is not present, go to step 21).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 18). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 19).
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 20). If continuity is not present, go to step 21).
Replace shorted HO2S. After replacing sensor, go to step 23).
Repair short to voltage in HO2S low circuit. After repairs, go to step 23).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 23).
Repair short to ground in HO2S low circuit. After repairs, go to step 23).
Repair short to voltage in signal circuit. After repairs, go to step 23).
Repair open or high resistance in signal circuit. After repairs, go to step 23).
Repair short to ground in signal circuit. After repairs, go to step 23).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 23). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0130 is set, go to step 2). If DTC P0130 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

HO2S pigtail or harness may be mispositioned and contacting exhaust system. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, corrosion or water intrusion.

An oxygen supply inside HO2S is necessary for proper operation. This supply of oxygen is provided through HO2S wiring harness. All HO2S wires and connections should be inspected for breaks or contamination. Repair as necessary.

Inspect for poor ECM to engine ground connections. If fuel pressure is too low, this DTC may set. Check for lean injectors. Inspect for disconnected or damaged vacuum hoses and for vacuum leaks at intake manifold, throttle body and crankcase ventilation system.

An exhaust leak may cause outside air to be pulled into exhaust gas stream past HO2S, causing this DTC to set. Check for exhaust leaks near HO2S.

Check for fuel contamination. Water, even in small amounts can be delivered to fuel injectors. Water can cause a lean condition to be indicated. Excessive alcohol in fuel can also cause this condition.

DTC P0131 - HO2S CIRCUIT LOW VOLTAGE BANK 1, SENSOR 1

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions required to set DTC are

HO2S voltage is less than -148 mV.
Condition is met for longer than 0.2 second.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and warm engine to normal operating temperature. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool remains less than -148 mV, go to step 4). If HO2S voltage value on scan tool does not remain less than -148 mV, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0131 is set, go to next step. If DTC P0131 is not set, see DIAGNOSTIC AIDS.
Turn ignition on, with engine off. Disconnect HO2S connector. Check for signs of water or corrosion. Repair as necessary. If HO2S voltage value on scan tool is 375-525 mV, go to step 14). If HO2S voltage value on scan tool is not 375-525 mV, go to next step.
Using DVOM, check voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 11).
Using DVOM, check voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to step 22). If voltage is not 700-800 mV, go to next step.
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect the 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting the other sensors restores voltage to 700-800 mV, go to step 14). If disconnecting one of the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector. Turn ignition on. Using DVOM, check voltage between ground and HO2S low circuit at ECM harness connector. If any voltage is present, go to step 15). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 16).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 17). If continuity is not present, go to step 21).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 18). If no voltage is present, go to next step.
Using DVOM, check continuity in HO2S signal circuit harness. If continuity is present, go to next step. If continuity is not present, go to step 19).
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 20). If continuity is not present, go to step 21).
Replace shorted HO2S. After replacing sensor, go to step 23).
Repair short to voltage in HO2S low circuit. After repairs, go to step 23).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 23).
Repair short to ground in HO2S low circuit. After repairs, go to step 23).
Repair short to voltage in signal circuit. After repairs, go to step 23).
Repair open or high resistance in signal circuit. After repairs, go to step 23).
Repair short to ground in signal circuit. After repairs, go to step 23).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 23). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0131 is set, go to step 2). If DTC P0131 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

DTC P0132 - HO2S CIRCUIT HIGH VOLTAGE BANK 1, SENSOR 1

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions for setting DTC

HO2S voltage is greater than 1083 mV.
Condition is met for longer than 0.2 second.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start engine and operate to normal operating temperature. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool remains greater than 1083 mV, go to step 4). If HO2S voltage value on scan tool does not remain greater than 1083 mV, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0132 is set, go to next step. If DTC P0132 is not set, see DIAGNOSTIC AIDS.
Turn ignition on, with engine off. Disconnect HO2S connector. Check for signs of water or corrosion. Repair as necessary. If HO2S voltage value on scan tool is 375-525 mV, go to step 14). If HO2S voltage value on scan tool is not 375-525 mV, go to next step.
Using DVOM, check voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 11).
Using DVOM, check voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to step 22). If voltage is not 700-800 mV, go to next step.
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting one of the other sensors restores voltage to 700-800 mV, go to step 14). If disconnecting one of the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S low circuit at ECM harness connector. If any voltage is present, go to step 15). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 16).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 17). If continuity is not present, go to step 21).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 18). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 19).
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 20). If continuity is not present, go to step 21).
Replace shorted HO2S. After replacing sensor, go to step 23).
Repair short to voltage in HO2S low circuit. After repairs are complete, go to step 23).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 23).
Repair short to ground in HO2S low circuit. After repairs are complete, go to step 23).
Repair short to voltage in signal circuit. After repairs, go to step 23).
Repair open or high resistance in signal circuit. After repairs, go to step 23).
Repair short to ground in signal circuit. After repairs, go to step 23).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 23). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0132 is set, go to step 2). If DTC P0132 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

HO2S pigtail or harness may be mispositioned and contacting exhaust system. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, corrosion or water intrusion.

DTC P0133 - HO2S SLOW RESPONSE BANK 1, SENSOR 1

Note. For circuit reference, see WIRING DIAGRAMS article.

Heated Oxygen Sensor (HO2S) produces a voltage that varies between -100 mV and 900 mV under normal operating conditions. Full operating range of HO2S circuit is about -406 mV to 1124 mV. ECM monitors this voltage and determines if exhaust is lean or rich. Oxygen sensor voltage is high when exhaust is rich, and low when exhaust is lean. ECM constantly monitors HO2S signal during closed loop operation and compensates for rich or lean condition by decreasing or increasing injector pulse width as necessary. If oxygen sensor is slow to respond to changes in exhaust oxygen content, this DTC will set.

Conditions required to set DTC are

HO2S average response rate is greater than 3.3 seconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
If DTC P0153 is present, go to step 7). If DTC P0153 is not present, go to next step.
Check exhaust system for leaks. Repair as necessary. After repairs, go to step 27). If no problem is found, go to next step.
Inspect for corrosion on HO2S terminals. Ensure HO2S is securely installed. Check terminal tension and for damaged wiring. Repair as necessary. After repairs, go to step 27). If no problem is found, go to next step.
Disconnect HO2S connector. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool is 375-525 mV, go to next step. If HO2S voltage value on scan tool is not 375-525 mV, go to step 8).
Jumper HO2S harness connector signal and low circuits to ground. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool is less than -100 mV, go to step 17). If HO2S voltage value on scan tool is greater than -100 mV, go to step 8).
Ensure the following conditions do not exist: fuel contamination, use of improper RTV sealant or engine oil or coolant consumption. Repair as necessary. After repairs, go to step 16). If none of these conditions exist, replace HO2S, then go to step 16).
Using DVOM, check voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 14).
Using DVOM, check voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to step 26). If voltage is not 700-800 mV, go to next step.
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect the 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting the other sensors restores voltage to 700-800 mV, go to step 18). If disconnecting one of the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S low circuit at ECM harness connector. If no voltage is present, go to next step. If any voltage is present, go to step 19).
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 20).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 21). If continuity is not present, go to step 25).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 22). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 23).
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 24). If continuity is not present, go to step 25).
Replace HO2S. After replacing sensor, go to step 27).
Replace shorted HO2S. After replacing sensor, go to step 27).
Repair short to voltage in HO2S low circuit. After repairs, go to step 27).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 27).
Repair short to ground in HO2S low circuit. After repairs, go to step 27).
Repair short to voltage in signal circuit. After repairs, go to step 27).
Repair open or high resistance in signal circuit. After repairs, go to step 27).
Repair short to ground in signal circuit. After repairs, go to step 27).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 27). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0133 is set, go to step 2). If DTC P0133 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

An oxygen supply inside HO2S is necessary for proper operation. This supply of oxygen is provided through HO2S wires. All HO2S wires and connections should be inspected for breaks or contamination. Repair as necessary.

Inspect for poor ECM to engine grounds. If fuel pressure is too low, this DTC may set. Check for lean injectors. Inspect for disconnected or damaged vacuum hoses and for vacuum leaks at intake manifold, throttle body and crankcase ventilation system.

An exhaust leak may cause outside air to be pulled into exhaust gas stream past HO2S, causing this DTC to set. Check for exhaust leaks near HO2S.

DTC P0134 - HO2S INSUFFICIENT ACTIVITY BANK 1, SENSOR 1

Note. For circuit reference, see WIRING DIAGRAMS article.

Heated Oxygen Sensor (HO2S) produces a voltage that varies between -100 mV and 900 mV under normal operating conditions. Full operating range of HO2S circuit is about from -406 mV to 1124 mV. ECM monitors this voltage and determines if exhaust is lean or rich. Oxygen sensor voltage is high when exhaust is rich, and low when exhaust is lean. ECM constantly monitors HO2S signal during closed loop operation and compensates for rich or lean condition by decreasing or increasing injector pulse width as necessary. If oxygen sensor cannot cause voltage to swing to less than 350 mV or greater than 555 mV, DTC will set.

Conditions for setting DTC

HO2S voltage stays between 350-555 mV for at least 3.5 seconds.
HO2S voltage is greater than 200 mV for at least 200 milliseconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Inspect for corrosion on HO2S terminals. Ensure HO2S is securely installed. Check terminal tension and for damaged wiring. Repair as necessary. After repairs, go to step 23). If no problem is found, go to next step.
Turn ignition on, with engine off. Disconnect HO2S connector. Using DVOM, check voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 10).
Using DVOM, check voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to next step. If voltage is not 700-800 mV, go to step 6).
Using a fused jumper, jumper HO2S harness connector signal circuit to ground. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool is -400 mV to -410 mV, go to step 20). If HO2S voltage value on scan tool is not -400 mV to -410 mV, go to step 22).
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect the 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting one of the other sensors restores voltage to 700-800 mV, go to step 13). If disconnecting one of the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector. Turn ignition on. Using DVOM, check voltage between ground and HO2S low circuit at ECM harness connector. If voltage is present, go to step 14). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 15).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 16). If continuity is not present, go to step 21).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 17). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 18).
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 19). If continuity is not present, go to step 21).
Replace shorted HO2S. After replacing sensor, go to step 23).
Repair short to voltage in HO2S low circuit. After repairs are complete, go to step 23).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 23).
Repair short to ground in HO2S low circuit. After repairs are complete, go to step 23).
Repair short to voltage in signal circuit. After repairs, go to step 23).
Repair open or high resistance in signal circuit. After repairs, go to step 23).
Repair short to ground in signal circuit. After repairs, go to step 23).
Replace HO2S. After replacing sensor, go to step 23).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 23). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0134 is set, go to step 2). If DTC P0134 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

An exhaust leak may cause outside air to be pulled into exhaust gas stream past HO2S, causing this DTC to set. Check for exhaust leaks near HO2S.

DTC P0135 - HO2S HEATER CIRCUIT BANK 1, SENSOR 1

Note. For circuit reference, see WIRING DIAGRAMS article.

Using Heated Oxygen Sensors (HO2S) for fuel control decreases amount of time required to enter closed loop operation. Heated oxygen sensors, when used post-catalyst, ensure sufficient heat is maintained for accurate catalyst monitoring.

When HO2S is cold, signal voltage at ECM is about 450 mV. When ignition is turned on, switched battery voltage is supplied to HO2S heaters via main relay. ECM controls heater operation by first modulating ground circuit when sensors are cold, then turning them on continuously after predetermined amount of time. This prevents possibility of thermal shock to sensors by controlling sensor's rate of heating. As heater reaches operating temperature, HO2S voltage responds by changing from bias voltage range to normal operation.

On cold start, ECM will track how much time it takes for HO2S voltage to go above or below bias voltage range. If ECM determines that it took too much time for HO2S to enter into normal operating range, this DTC will set. The time it takes HO2S to reach operating temperature is based on amount of airflow into engine and start-up coolant temperature.

Conditions required to set DTC are

ECM calculated HO2S heater resistance greater than 9.56 ohms or less than 2.45 ohms.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Disconnect HO2S connector. Turn ignition on. Using test light connected to ground, probe HO2S harness connector switched battery feed circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step 4).
Start engine. Using test light connected to battery voltage, probe HO2S harness connector heater control circuit. If test light illuminates, go to step 9). If test light does not illuminate, go to step 8).
Check HO2S heater fuse. If fuse is okay, go to next step. If fuse is blown, go to step 6).
Using test light connected to ground, check for power at HO2S fuse. If test light illuminates, go to step 11). If test light does not illuminate, go to step 12).
Disconnect other front HO2S connector. Using test light connected to battery voltage, probe HO2S harness connector switched battery feed circuit. If test light illuminates, go to step 13). If test light does not illuminate, go to next step.
Using DVOM, check resistance of both front HO2S heaters at sensor pigtails. If resistance of both heaters is greater than 4 ohms, see DIAGNOSTIC AIDS. If resistance of both heaters is not greater than 4 ohms, go to step 14).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check continuity of heater control circuit between HO2S and ECM harness connectors. If continuity is present, go to step 16). If continuity is not present, go to step 15).
Check for poor connections and terminal tension at HO2S harness connector. Repair as necessary. After repairs, go to step 18). If connections and terminals are okay, go to next step.
Replace HO2S. After replacing sensor, go to step 18).
Repair open or high resistance in switched battery feed circuit between fuse and HO2S. After repairs, go to step 18).
Repair feed circuit to fuse. After repairs, go to step 18).
Repair short to ground in switched battery feed circuit. After repairs, go to step 18).
Replace HO2S with low resistance heater. After replacing sensor, go to step 18).
Repair open or high resistance in heater control circuit. After repairs, go to step 18).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 18). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0135 is set, go to step 2). If DTC P0135 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

DTC P0136 - HO2S CIRCUIT BANK 1, SENSOR 2

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions required to set DTC are

HO2S voltage is between -39.8 mV and 38.3 mV.
Condition is met for longer than 4 minutes.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start engine and run to normal operating temperature. Using scan tool, monitor HO2S voltage. If HO2S voltage on scan tool remains less than 399 mV, go to step 4). If HO2S voltage on scan tool does not remain less than 399 mV, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0136 is set, go to next step. If DTC P0136 is not set, see DIAGNOSTIC AIDS.
Turn ignition on, with engine off. Disconnect HO2S connector. Check for signs of water or corrosion. Repair as necessary. If HO2S voltage value on scan tool is 375-525 mV, go to step 14). If HO2S voltage value on scan tool is not 375-525 mV, go to next step.
Using DVOM, measure voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 11).
Using DVOM, measure voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to step 22). If voltage is not 700-800 mV, go to next step.
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting one of the other sensors restores voltage to 700-800 mV, go to step 14). If disconnecting one of the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM connector located in engine compartment relay center. Turn ignition on. Using DVOM, measure voltage between ground and HO2S low circuit at ECM harness connector. If any voltage is present, go to step 15). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 16).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 17). If continuity is not present, go to step 21).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM connector located in engine compartment relay center. Turn ignition on. Using DVOM, measure voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 18). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 19).
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 20). If continuity is not present, go to step 21).
Replace shorted HO2S. After repairs, go to step 23).
Repair short to voltage in HO2S low circuit. After repairs, go to step 23).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 23).
Repair short to ground in HO2S low circuit. After repairs, go to step 23).
Repair short to voltage in signal circuit. After repairs, go to step 23).
Repair open or high resistance in signal circuit. After repairs, go to step 23).
Repair short to ground in signal circuit. After repairs, go to step 23).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 23). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0136 is set, go to step 2). If DTC P0136 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

An exhaust leak may cause outside air to be pulled into exhaust gas stream past HO2S, causing this DTC to set. Check for exhaust leaks near HO2S.

DTC P0137 - HO2S CIRCUIT VOLTAGE LOW BANK 1, SENSOR 2

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions required to set DTC are

HO2S voltage is less than -148 mV.
Condition is met for longer than 0.2 second.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start engine and operate vehicle to normal operating temperature. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool remains less than -148 mV, go to step 4). If HO2S voltage value on scan tool does not remain less than -148 mV, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0137 is set, go to next step. If DTC P0137 is not set, see DIAGNOSTIC AIDS.
Turn ignition on, with engine off. Disconnect HO2S connector. Check for signs of water or corrosion. Repair as necessary. If HO2S voltage value on scan tool is 375-525 mV, go to step 14). If HO2S voltage value on scan tool is not 375-525 mV, go to next step.
Using DVOM, check voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 11).
Using DVOM, check voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to step 22). If voltage is not 700-800 mV, go to next step.
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect the 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting the other sensors restores voltage to 700-800 mV, go to step 14). If disconnecting one of the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S connector disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S low circuit at ECM harness connector. If any voltage is present, go to step 15). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 16).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 17). If continuity is not present, go to step 21).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 18). If no voltage is present, go to next step.
Using DVOM, check continuity of HO2S signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 19).
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 20). If continuity is not present, go to step 21).
Replace shorted HO2S. After replacing sensor, go to step 23).
Repair short to voltage in HO2S low circuit. After repairs, go to step 23).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 23).
Repair short to ground in HO2S low circuit. After repairs, go to step 23).
Repair short to voltage in signal circuit. After repairs, go to step 23).
Repair open or high resistance in signal circuit. After repairs, go to step 23).
Repair short to ground in signal circuit. After repairs, go to step 23).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 23). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0137 is set, go to step 2). If DTC P0137 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

For any test that requires probing ECM or component harness connector, use Connector Test Adapter Kit (J-35616-A). This will prevent damage to harness connector terminals. Check for the following conditions

DTC P0138 - HO2S CIRCUIT VOLTAGE HIGH BANK 1, SENSOR 2

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions required to set DTC are

HO2S voltage is above 1083 mV.
Condition is met for longer than 0.2 second.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and warm engine to normal operating temperature. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool remains greater than 1083 mV, go to step 4). If HO2S voltage value on scan tool does not remain greater than 1083 mV, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0138 is set, go to next step. If DTC P0138 is not set, see DIAGNOSTIC AIDS.
Turn ignition on, with engine off. Disconnect HO2S connector. Check for signs of water or corrosion. Repair as necessary. If HO2S voltage value on scan tool is 375-525 mV, go to step 14). If HO2S voltage value on scan tool is not 375-525 mV, go to next step.
Using DVOM, check voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 11).
Using DVOM, check voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to step 22). If voltage is not 700-800 mV, go to next step.
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect the 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting the other sensors restores voltage to 700-800 mV, go to step 14). If disconnecting one of the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector. Turn ignition on. Using DVOM, check voltage between ground and HO2S low circuit at ECM harness connector. If any voltage is present, go to step 15). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 16).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 17). If continuity is not present, go to step 21).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 18). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 19).
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 20). If continuity is not present, go to step 21).
Replace shorted HO2S. After replacing sensor, go to step 23).
Repair short to voltage in HO2S low circuit. After repairs, go to step 23).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 23).
Repair short to ground in HO2S low circuit. After repairs, go to step 23).
Repair short to voltage in signal circuit. After repairs, go to step 23).
Repair open or high resistance in signal circuit. After repairs, go to step 23).
Repair short to ground in signal circuit. After repairs, go to step 23).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 23). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0138 is set, go to step 2). If DTC P0138 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

DTC P0140 - HO2S INSUFFICIENT ACTIVITY BANK 1, SENSOR 2

Note. For circuit reference, see WIRING DIAGRAMS article.

Heated Oxygen Sensor (HO2S) produces a voltage that varies between -100 mV and 900 mV under normal operating conditions. Full operating range of HO2S circuit is about from -406 mV to 1124 mV. ECM monitors this voltage and determines if exhaust is lean or rich. Oxygen sensor voltage is high when exhaust is rich, and low when exhaust is lean. ECM constantly monitors HO2S signal during closed loop operation and compensates for rich or lean condition by decreasing or increasing injector pulse width as necessary. If oxygen sensor cannot cause voltage to swing to less than 350 mV or greater than 555 mV, this DTC will set.

Conditions required to set DTC are

HO2S voltage stays 393-501 mV for at least 10 minutes.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Inspect for corrosion on HO2S terminals. Ensure HO2S is securely installed. Check terminal tension and for damaged wiring. Repair as necessary. After repairs, go to step 23). If no problem is found, go to next step.
Turn ignition on, with engine off. Disconnect HO2S connector. Using DVOM, check voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 10).
Using DVOM, check voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to next step. If voltage is not 700-800 mV, go to step 6).
Using a fused jumper, jumper HO2S harness connector signal circuit to ground. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool is -400 mV to -410 mV, go to step 20). If HO2S voltage value on scan tool is not -400 mV to -410 mV, go to step 22).
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect the 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting the other sensors restores voltage to 700-800 mV, go to step 13). If disconnecting one of the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S low circuit at ECM harness connector. If voltage is present, go to step 14). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 15).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 16). If continuity is not present, go to step 21).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 17). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 18).
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 19). If continuity is not present, go to step 21).
Replace shorted HO2S. After replacing sensor, go to step 23).
Repair short to voltage in HO2S low circuit. After repairs are complete, go to step 23).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 23).
Repair short to ground in HO2S low circuit. After repairs are complete, go to step 23).
Repair short to voltage in signal circuit. After repairs, go to step 23).
Repair open or high resistance in signal circuit. After repairs, go to step 23).
Repair short to ground in signal circuit. After repairs, go to step 23).
Replace HO2S. After replacing sensor, go to step 23).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 23). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0140 is set, go to step 2). If DTC P0140 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

An exhaust leak may cause outside air to be pulled into exhaust gas stream past HO2S, causing this DTC to set. Check for exhaust leaks near HO2S.

DTC P0141 - HO2S HEATER CIRCUIT BANK 1, SENSOR 2

Note. For circuit reference, see WIRING DIAGRAMS article.

Using Heated Oxygen Sensors (HO2S) for fuel control decreases amount of time required to enter closed loop operation. Heated oxygen sensors when used post-catalyst, ensure sufficient heat is maintained for accurate catalyst monitoring.

Conditions for setting DTC

ECM calculated HO2S heater resistance greater than 9.56 ohms or less than 2.45 ohms.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Disconnect HO2S connector. Using test light connected to ground, probe HO2S harness connector switched battery feed circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step 4).
Start engine. Using test light connected to battery voltage, probe HO2S harness connector heater control circuit. If test light illuminates, go to step 9). If test light does not illuminate, go to step 8).
Check HO2S heater fuse. If fuse is okay, go to next step. If fuse is blown, go to step 6).
Using test light connected to ground, check for power at HO2S fuse. If test light illuminates, go to step 11). If test light does not illuminate, go to step 12).
Disconnect other front HO2S connector. Using test light connected to battery voltage, probe HO2S harness connector switched battery feed circuit. If test light illuminates, go to step 13). If test light does not illuminate, go to next step.
Using DVOM, measure resistance of both front HO2S heaters at sensor pigtails. If resistance of both heaters is greater than 4 ohms, see DIAGNOSTIC AIDS. If resistance of both heaters is less than 4 ohms, go to step 14).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check continuity of heater control circuit between HO2S and ECM harness connectors. If continuity is present, go to step 16). If continuity is not present, go to step 15).
Check for poor connections and terminal tension at HO2S harness connector. Repair as necessary. After repairs, go to step 18). If connections and terminals are okay, go to next step.
Replace HO2S. After replacing sensor, go to step 18).
Repair open or high resistance in switched battery feed circuit between fuse and HO2S. After repairs, go to step 18).
Repair feed circuit to fuse. After repairs, go to step 18).
Repair short to ground in switched battery feed circuit. After repairs, go to step 18).
Replace HO2S with low resistance heater. After replacing sensor, go to step 18).
Repair open or high resistance in heater control circuit. After repairs are complete, go to step 18).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 18). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0141 is set, go to step 2). If DTC P0141 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

DTC P0150 - HO2S CIRCUIT BANK 2, SENSOR 1

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions required to set DTC are

HO2S voltage is 62-399 mV.
Condition is met for longer than 20 seconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start engine and operate to normal operating temperature. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool remains less than 399 mV, go to step 4). If HO2S voltage value on scan tool does not remain less than 399 mV, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0150 is set, go to next step. If DTC P0150 is not set, see DIAGNOSTIC AIDS.
Turn ignition on, with engine off. Disconnect HO2S connector. Check for signs of water or corrosion. Repair as necessary. If HO2S voltage value on scan tool is 375-525 mV, go to step 14). If HO2S voltage value on scan tool is not 375-525 mV, go to next step.
Using DVOM, check voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 11).
Using DVOM, check voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to step 22). If voltage is not 700-800 mV, go to next step.
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect the 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting one of the other sensors restores voltage to 700-800 mV, go to step 14). If disconnecting the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector. Turn ignition on. Using DVOM, check voltage between ground and HO2S low circuit at ECM harness connector. If any voltage is present, go to step 15). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 16).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 17). If continuity is not present, go to step 21).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 18). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 19).
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 20). If continuity is not present, go to step 21).
Replace shorted HO2S. After replacing sensor, go to step 23).
Repair short to voltage in HO2S low circuit. After repairs, go to step 23).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 23).
Repair short to ground in HO2S low circuit. After repairs, go to step 23).
Repair short to voltage in signal circuit. After repairs, go to step 23).
Repair open or high resistance in signal circuit. After repairs, go to step 23).
Repair short to ground in signal circuit. After repairs, go to step 23).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 23). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0150 is set, go to step 2). If DTC P0150 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Inspect for poor ECM-to-engine grounds. If fuel pressure is too low, this DTC may set. Check for lean injectors. Inspect for disconnected or damaged vacuum hoses and for vacuum leaks at intake manifold, throttle body and crankcase ventilation system.

An exhaust leak may cause outside air to be pulled into exhaust gas stream past HO2S, causing this DTC to set. Check for exhaust leaks near HO2S.

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

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions required to set DTC are

HO2S voltage is less than -148 mV.
Condition is met for longer than 0.2 second.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start engine and operate to normal operating temperature. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool remains less than -148 mV, go to step 4). If HO2S voltage value on scan tool does not remain less than -148 mV, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0151 is set, go to next step. If DTC P0151 is not set, see DIAGNOSTIC AIDS.
Turn ignition on, with engine off. Disconnect HO2S connector. Check for signs of water or corrosion. Repair as necessary. If HO2S voltage value on scan tool is 375-525 mV, go to step 14). If HO2S voltage value on scan tool is not 375-525 mV, go to next step.
Using DVOM, measure voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 11).
Using DVOM, measure voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to step 22). If voltage is not 700-800 mV, go to next step.
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect the 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting the other sensors restores voltage to 700-800 mV, go to step 14). If disconnecting one of the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM connector located in engine compartment, in relay center. Turn ignition on. Using DVOM, measure voltage between ground and HO2S low circuit at ECM harness connector. If any voltage is present, go to step 15). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 16).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 17). If continuity is not present, go to step 21).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM connector located in engine compartment, in relay center. Turn ignition on. Using DVOM, measure voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 18). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 19).
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 20). If continuity is not present, go to step 21).
Replace shorted HO2S. After replacing sensor, go to step 23).
Repair short to voltage in HO2S low circuit. After repairs, go to step 23).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 23).
Repair short to ground in HO2S low circuit. After repairs, go to step 23).
Repair short to voltage in signal circuit. After repairs, go to step 23).
Repair open or high resistance in signal circuit. After repairs, go to step 23).
Repair short to ground in signal circuit. After repairs, go to step 23).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 23). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0151 is set, go to step 2). If DTC P0151 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

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

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions for setting DTC

HO2S voltage is greater than 1083 mV.
Condition is met for more than 0.2 second.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start engine and operate to normal operating temperature. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool remains greater than 1083 mV, go to step 4). If HO2S voltage value on scan tool does not remain greater than 1083 mV, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0152 is set, go to next step. If DTC P0152 is not set, see DIAGNOSTIC AIDS.
Turn ignition on, with engine off. Disconnect HO2S connector. Check for signs of water or corrosion. Repair as necessary. If HO2S voltage value on scan tool is 375-525 mV, go to step 14). If HO2S voltage value on scan tool is not 375-525 mV, go to next step.
Using DVOM, measure voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 11).
Using DVOM, check voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to step 22). If voltage is not 700-800 mV, go to next step.
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting the other sensors restores voltage to 700-800 mV, go to step 14). If disconnecting one of the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM connector located in engine compartment, in relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S low circuit at ECM harness connector. If any voltage is present, go to step 15). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 16).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 17). If continuity is not present, go to step 21).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM connector located in engine compartment, in relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 18). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 19).
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 20). If continuity is not present, go to step 21).
Replace shorted HO2S. After replacing sensor, go to step 23).
Repair short to voltage in HO2S low circuit. After repairs, go to step 23).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 23).
Repair short to ground in HO2S low circuit. After repairs, go to step 23).
Repair short to voltage in signal circuit. After repairs, go to step 23).
Repair open or high resistance in signal circuit. After repairs, go to step 23).
Repair short to ground in signal circuit. After repairs, go to step 23).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 23). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0152 is set, go to step 2). If DTC P0152 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

DTC P0153 - HO2S SLOW RESPONSE BANK 2, SENSOR 1

Note. For circuit reference, see WIRING DIAGRAMS article.

Heated Oxygen Sensor (HO2S) produces a voltage that varies between -100 mV and 900 mV under normal operating conditions. Full operating range of HO2S circuit is about from -406 mV to 1124 mV. ECM monitors this voltage and determines if exhaust is lean or rich. Oxygen sensor voltage is high when exhaust is rich, and low when exhaust is lean. ECM constantly monitors HO2S signal during closed loop operation and compensates for rich or lean condition by decreasing or increasing injector pulse width as necessary. If oxygen sensor is slow to respond to changes in exhaust oxygen content, this DTC will set.

Conditions required to set DTC are

HO2S average response rate is greater than 3.3 seconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
If DTC P0133 is present, go to step 7). If DTC P0133 is not present, go to next step.
Check exhaust system for leaks. Repair as necessary. After repairs, go to step 27). If no problem is found, go to next step.
Inspect for corrosion on HO2S terminals. Ensure HO2S is securely installed. Check terminal tension and for damaged wiring. Repair as necessary. After repairs, go to step 27). If no problem is found, go to next step.
Disconnect HO2S connector. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool is 375-525 mV, go to next step. If HO2S voltage value on scan tool is not 375-525 mV, go to step 8).
Jumper HO2S harness connector signal and low circuits to ground. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool is less than -100 mV, go to step 17). If HO2S voltage value on scan tool is greater than -100 mV, go to step 8).
Ensure the following conditions do not exist: fuel contamination, use of improper RTV sealant or engine oil or coolant consumption. Repair as necessary. After repairs, go to step 16). If none of these conditions exist, replace HO2S, then go to step 16).
Using DVOM, measure voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 14).
Using DVOM, measure voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to step 26). If voltage is not 700-800 mV, go to next step.
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting the other sensors restores voltage to 700-800 mV, go to step 18). If disconnecting one of the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S low circuit at ECM harness connector. If voltage is present, go to step 19). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 20).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 21). If continuity is not present, go to step 25).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 22). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 23).
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 24). If continuity is not present, go to step 25).
Replace HO2S. After replacing sensor, go to step 27).
Replace shorted HO2S. After repairs, go to step 27).
Repair short to voltage in HO2S low circuit. After repairs, go to step 27).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 27).
Repair short to ground in HO2S low circuit. After repairs, go to step 27).
Repair short to voltage in signal circuit. After repairs, go to step 27).
Repair open or high resistance in signal circuit. After repairs, go to step 27).
Repair short to ground in signal circuit. After repairs, go to step 27).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 27). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0153 is set, go to step 2). If DTC P0153 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

An exhaust leak may cause outside air to be pulled into exhaust gas stream past HO2S, causing this DTC to set. Check for exhaust leaks near HO2S.

DTC P0154 - HO2S INSUFFICIENT ACTIVITY BANK 2, SENSOR 1

Note. For circuit reference, see WIRING DIAGRAMS article.

Heated Oxygen Sensor (HO2S) produces a voltage that varies between -100 mV and 900 mV under normal operating conditions. Full operating range of HO2S circuit is about from -406 mV to 1124 mV. ECM monitors this voltage and determines if exhaust is lean or rich. Oxygen sensor voltage is high when exhaust is rich, and low when exhaust is lean. ECM constantly monitors HO2S signal during closed loop operation and compensates for rich or lean condition by decreasing or increasing injector pulse width as necessary. If oxygen sensor cannot cause voltage to swing to less than 350 mV or greater than 555 mV, this DTC will set.

Conditions required to set DTC are

HO2S voltage stays 350-555 mV for at least 3.5 seconds.
HO2S voltage is greater than 200 mV for at least 200 milliseconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Inspect for corrosion on HO2S terminals. Ensure HO2S is securely installed. Check terminal tension and for damaged wiring. Repair as necessary. After repairs, go to step 23). If no problem is found, go to next step.
Turn ignition on, with engine off. Disconnect HO2S connector. Using DVOM, measure voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 10).
Using DVOM, check voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to next step. If voltage is not 700-800 mV, go to step 6).
Using a fused jumper, jumper HO2S harness connector signal circuit to ground. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool is -400 mV to -410 mV, go to step 20). If HO2S voltage value on scan tool is not -400 mV to -410 mV, go to step 22).
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect the 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting the other sensors restores voltage to 700-800 mV, go to step 13). If disconnecting one of the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S connectors disconnected. Turn ignition off. Disconnect ECM harness connector. Turn ignition on. Using DVOM, check voltage between ground and HO2S low circuit at ECM harness connector. If any voltage is present, go to step 14). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 15).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 16). If continuity is not present, go to step 21).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 17). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 18).
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 19). If continuity is not present, go to step 21).
Replace shorted HO2S. After replacing sensor, go to step 23).
Repair short to voltage in HO2S low circuit. After repairs, go to step 23).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 23).
Repair short to ground in HO2S low circuit. After repairs, go to step 23).
Repair short to voltage in signal circuit. After repairs, go to step 23).
Repair open or high resistance in signal circuit. After repairs, go to step 23).
Repair short to ground in signal circuit. After repairs, go to step 23).
Replace HO2S. After replacing sensor, go to step 23).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 23). If connections and terminals are okay, go to next step.
Replace ECM. NEW ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0154 is set, go to step 2). If DTC P0154 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

An exhaust leak may cause outside air to be pulled into exhaust gas stream past HO2S, causing this DTC to set. Check for exhaust leaks near HO2S.

DTC P0155 - HO2S HEATER CIRCUIT BANK 2, SENSOR 1

Note. For circuit reference, see WIRING DIAGRAMS article.

When HO2S is cold, signal voltage at ECM is about 450 mV. When ignition is turned to on position, switched battery voltage is supplied to HO2S heaters via main relay. ECM controls heater operation by first modulating ground circuit when sensors are cold, then turning them on continuously after predetermined amount of time. This prevents possibility of thermal shock to sensors by controlling sensor's rate of heating. As heater reaches operating temperature, HO2S voltage responds by changing from bias voltage range to normal operation.

Conditions required to set DTC are

ECM calculated HO2S heater resistance greater than 9.56 ohms or less than 2.45 ohms.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Disconnect HO2S connector. Using test light connected to ground, probe HO2S harness connector switched battery feed circuit. If test light is on, go to next step. If test light is off, go to step 4).
Start engine. Using test light connected to battery voltage, probe HO2S harness connector heater control circuit. If test light is on, go to step 9). If test light is off, go to step 8).
Check HO2S heater fuse. If fuse is okay, go to next step. If fuse is blown, go to step 6).
Using test light connected to ground, check for power at HO2S fuse. If test light is on, go to step 11). If test light is off, go to step 12).
Disconnect other front HO2S connector. Using test light connected to battery voltage, probe HO2S harness connector switched battery feed circuit. If test light is on, go to step 13). If test light is off, go to next step.
Using DVOM, measure resistance of both front HO2S heaters at sensor pigtails. If resistance of both heaters is greater than 4 ohms, see DIAGNOSTIC AIDS. If resistance of both heaters is less than 4 ohms, go to step 14).
Turn ignition off. Disconnect ECM located in engine compartment relay center. Using DVOM, check continuity of heater control circuit between HO2S and ECM harness connectors. If continuity is present, go to step 16). If continuity is not present, go to step 15).
Check for poor connections and terminal tension at HO2S harness connector. Repair as necessary. After repairs, go to step 18). If connections and terminals are okay, go to next step.
Replace HO2S. After replacing sensor, go to step 18).
Repair open or high resistance in switched battery feed circuit between fuse and HO2S. After repairs, go to step 18).
Repair feed circuit to fuse. After repairs, go to step 18).
Repair short to ground in switched battery feed circuit. After repairs, go to step 18).
Replace HO2S with low resistance heater. After replacing sensor, go to step 18).
Repair open or high resistance in heater control circuit. After repairs, go to step 18).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 18). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0155 is set, go to step 2). If DTC P0155 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

DTC P0156 - HO2S CIRCUIT BANK 2, SENSOR 2

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions for setting DTC

HO2S voltage is between 62-399 mV.
Condition is met for more than 20 seconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and warm engine to normal operating temperature. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool remains less than 399 mV, go to step 4). If HO2S voltage value on scan tool does not remain less than 399 mV, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0156 is set, go to next step. If DTC P0156 is not set, see DIAGNOSTIC AIDS.
Turn ignition on, with engine off. Disconnect HO2S connector. Check for signs of water or corrosion. Repair as necessary. If HO2S voltage value on scan tool is 375-525 mV, go to step 14). If HO2S voltage value on scan tool is not 375-525 mV, go to next step.
Using DVOM, measure voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 11).
Using DVOM, check voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to step 22). If voltage is not 700-800 mV, go to next step.
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect the 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting the other sensors restores voltage to 700-800 mV, go to step 14). If disconnecting one of the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S low circuit at ECM harness connector. If no voltage is present, go to next step. If voltage is present, go to step 15).
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 16).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 17). If continuity is not present, go to step 21).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 18). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 19).
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 20). If continuity is not present, go to step 21).
Replace shorted HO2S. After replacing sensor, go to step 23).
Repair short to voltage in HO2S low circuit. After repairs, go to step 23).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 23).
Repair short to ground in HO2S low circuit. After repairs, go to step 23).
Repair short to voltage in signal circuit. After repairs, go to step 23).
Repair open or high resistance in signal circuit. After repairs, go to step 23).
Repair short to ground in signal circuit. After repairs, go to step 23).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 23). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0156 is set, go to step 2). If DTC P0156 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

An exhaust leak may cause outside air to be pulled into exhaust gas stream past HO2S, causing this DTC to set. Check for exhaust leaks near HO2S.

DTC P0157 - HO2S CIRCUIT VOLTAGE LOW BANK 2, SENSOR 2

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions for setting DTC

HO2S voltage is below -148 mV.
Condition is met for longer than 0.2 second.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and operate engine to normal operating temperature. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool remains less than -148 mV, go to step 4). If HO2S voltage value on scan tool does not remain less than -148 mV, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0157 is set, go to next step. If DTC P0157 is not set, see DIAGNOSTIC AIDS.
Turn ignition on, with engine off. Disconnect HO2S connector. Check for signs of water or corrosion. Repair as necessary. If HO2S voltage value on scan tool is 375-525 mV, go to step 14). If HO2S voltage value on scan tool is not 375-525 mV, go to next step.
Using DVOM, check voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 11).
Using DVOM, check voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to step 22). If voltage is not 700-800 mV, go to next step.
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting the other sensors restores voltage to 700-800 mV, go to step 14). If disconnecting one of the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S low circuit at ECM harness connector. If no voltage is present, go to next step. If any voltage is present, go to step 15).
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 16).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 17). If continuity is not present, go to step 21).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 18). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 19).
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 20). If continuity is not present, go to step 21).
Replace shorted HO2S. After replacing sensor, go to step 23).
Repair short to voltage in HO2S low circuit. After repairs, go to step 23).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 23).
Repair short to ground in HO2S low circuit. After repairs, go to step 23).
Repair short to voltage in signal circuit. After repairs, go to step 23).
Repair open or high resistance in signal circuit. After repairs, go to step 23).
Repair short to ground in signal circuit. After repairs, go to step 23).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 23). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0157 is set, go to step 2). If DTC P0157 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

DTC P0158 - HO2S CIRCUIT VOLTAGE HIGH BANK 2, SENSOR 2

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions required to set DTC are

HO2S voltage is greater than 1083 mV.
Condition is met for more than 0.2 second.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and operate engine to normal operating temperature. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool remains greater than 1083 mV, go to step 4). If HO2S voltage value on scan tool does not remain greater than 1083 mV, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0158 is set, go to next step. If DTC P0158 is not set, see DIAGNOSTIC AIDS.
Turn ignition on, with engine off. Disconnect HO2S connector. Check for signs of water or corrosion. Repair as necessary. If HO2S voltage value on scan tool is 375-525 mV, go to step 14). If HO2S voltage value on scan tool is not 375-525 mV, go to next step.
Using DVOM, check voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 11).
Using DVOM, check voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to step 22). If voltage is not 700-800 mV, go to next step.
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect the 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting one of the other sensors restores voltage to 700-800 mV, go to step 14). If disconnecting one of the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S low circuit at ECM harness connector. If no voltage is present, go to next step. If any voltage is present, go to step 15).
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 16).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 17). If continuity is not present, go to step 21).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 18). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 19).
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 20). If continuity is not present, go to step 21).
Replace shorted HO2S. After replacing sensor, go to step 23).
Repair short to voltage in HO2S low circuit. After repairs, go to step 23).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 23).
Repair short to ground in HO2S low circuit. After repairs, go to step 23).
Repair short to voltage in signal circuit. After repairs, go to step 23).
Repair open or high resistance in signal circuit. After repairs, go to step 23).
Repair short to ground in signal circuit. After repairs, go to step 23).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 23). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0158 is set, go to step 2). If DTC P0158 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

DTC P0160 - HO2S INSUFFICIENT ACTIVITY BANK 2, SENSOR 2

Note. For circuit reference, see WIRING DIAGRAMS article.

Heated Oxygen Sensor (HO2S) produces a voltage that varies between -100 mV and 900 mV under normal operating conditions. Full operating range of HO2S circuit is about from -406 mV to 1124 mV. ECM monitors this voltage and determines if exhaust is lean or rich. Oxygen sensor voltage is high when exhaust is rich, and low when exhaust is lean. ECM constantly monitors HO2S signal during closed loop operation and compensates for rich or lean condition by decreasing or increasing injector pulse width as necessary. If oxygen sensor cannot cause voltage to swing below 350 mV or above 555 mV, this DTC will set.

Conditions for setting DTC

HO2S voltage stays between 350-555 mV for at least 3.5 seconds.
HO2S voltage is greater than 200 mV for at least 200 milliseconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Inspect for corrosion on HO2S terminals. Ensure HO2S is securely installed. Check terminal tension and for damaged wiring. Repair as necessary. After repairs, go to step 23). If no problem is found, go to next step.
Turn ignition on, with engine off. Disconnect HO2S connector. Using DVOM, check voltage between ground and signal circuit at HO2S harness connector. If voltage is 900-1100 mV, go to next step. If voltage is not 900-1100 mV, go to step 10).
Using DVOM, check voltage between ground and low circuit at HO2S harness connector. If voltage is 700-800 mV, go to next step. If voltage is not 700-800 mV, go to step 6).
Using a fused jumper, jumper HO2S harness connector signal circuit to ground. Using scan tool, monitor HO2S voltage. If HO2S voltage value on scan tool is -400 mV to -410 mV, go to step 20). If HO2S voltage value on scan tool is not -400 mV to -410 mV, go to step 22).
Continue to monitor DVOM voltage from HO2S low circuit between harness connector and ground. Disconnect the 3 other HO2S. As each sensor is disconnected, recheck voltage on DVOM. If disconnecting the other sensors restores voltage to 700-800 mV, go to step 13). If disconnecting one of the other sensors does not restore voltage to 700-800 mV, go to next step.
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM connector located in engine compartment, in relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S low circuit at ECM harness connector. If any voltage is present, go to step 14). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S low circuit. If continuity is present, go to next step. If continuity is not present, go to step 15).
Using DVOM, check harness continuity between HO2S low circuit and ground. If continuity is present, go to step 16). If continuity is not present, go to step 21).
Leave all HO2S disconnected. Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and HO2S signal circuit at ECM harness connector. If any voltage is present, go to step 17). If no voltage is present, go to next step.
Using DVOM, check harness continuity of HO2S signal circuit. If continuity is not present, go to step 18). If continuity is present, go to next step.
Using DVOM, check harness continuity between HO2S signal circuit and ground. If continuity is present, go to step 19). If continuity is not present, go to step 21).
Replace shorted HO2S. After replacing sensor, go to step 23).
Repair short to voltage in HO2S low circuit. After repairs, go to step 23).
Repair open or high resistance in HO2S low circuit. After repairs, go to step 23).
Repair short to ground in HO2S low circuit. After repairs, go to step 23).
Repair short to voltage in signal circuit. After repairs, go to step 23).
Repair open or high resistance in signal circuit. After repairs, go to step 23).
Repair short to ground in signal circuit. After repairs, go to step 23).
Replace HO2S. After replacing sensor, go to step 23).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 23). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0160 is set, go to step 2). If DTC P0160 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

An exhaust leak may cause outside air to be pulled into exhaust gas stream past HO2S, causing this DTC to set. Check for exhaust leaks near HO2S.

DTC P0161 - HO2S HEATER CIRCUIT BANK 2, SENSOR 2

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions required to set DTC are

ECM calculated HO2S heater resistance greater than 9.56 ohms or less than 2.45 ohms.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Disconnect HO2S connector. Using test light connected to ground, probe HO2S harness connector switched battery feed circuit. If test light is on, go to next step. If test light is off, go to step 4).
Start engine. Using test light connected to battery voltage, probe HO2S harness connector heater control circuit. If test light is on, go to step 9). If test light is off, go to step 8).
Check HO2S heater fuse. If fuse is okay, go to next step. If fuse is blown, go to step 6).
Using test light connected to ground, check for power at HO2S fuse. If test light is on, go to step 11). If test light is off, go to step 12).
Disconnect other front HO2S connector. Using test light connected to battery voltage, probe HO2S harness connector switched battery feed circuit. If test light is on, go to step 13). If test light is off, go to next step.
Using DVOM, check resistance of both front HO2S heaters at sensor pigtails. If resistance of both heaters is greater than 4 ohms, see DIAGNOSTIC AIDS. If resistance of both heaters is less than 4 ohms, go to step 14).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check continuity of heater control circuit between HO2S and ECM harness connectors. If continuity is present, go to step 16). If continuity is not present, go to step 15).
Check for poor connections and terminal tension at HO2S harness connector. Repair as necessary. After repairs, go to step 18). If connections and terminals are okay, go to next step.
Replace HO2S. After replacing sensor, go to step 18).
Repair open or high resistance in switched battery feed circuit between fuse and HO2S. After repairs, go to step 18).
Repair feed circuit to fuse. After repairs, go to step 18).
Repair short to ground in switched battery feed circuit. After repairs, go to step 18).
Replace HO2S with low resistance heater. After replacing sensor, go to step 18).
Repair open or high resistance in heater control circuit. After repairs, go to step 18).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 18). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0161 is set, go to step 2). If DTC P0161 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

DTC P0171 - FUEL TRIM SYSTEM LEAN, BANK 1

Note. For circuit reference, see WIRING DIAGRAMS article.

To provide the best possible combination of driveability, fuel economy and emission control, a closed loop air/fuel metering system is used. While in closed loop, ECM monitors heated oxygen sensor signal voltage and adjusts fuel delivery based on signal voltage. A change made in fuel delivery will be indicated by long and short term fuel trim values. Short term fuel trim values change rapidly in response to HO2S signal voltages. These changes fine tune engine fueling.

Long term fuel trim values change in response to trends in short term fuel trim. Long term fuel trim makes coarse adjustments to fueling in order to re-center and restore control to short term fuel trim. Short and long term fuel trim can be monitored with a scan tool. Ideal fuel trim values are around zero percent. A positive fuel trim value indicates ECM is adding fuel to compensate for lean condition. A negative fuel trim value indicates ECM is reducing amount of fuel to compensate for rich condition.

If an excessively rich or lean condition is detected, ECM will set a DTC. Long term (additive and multiplicative) fuel trim diagnostic parameter is a calculated value from several of long term speed loan learn cells which are selected based on speed and load.

Conditions for setting DTC

ECM detects fuel trim values greater than 550 milliseconds for additive fuel trim or greater than 23 percent for multiplicative fuel trim.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
If any other DTCs are set, except DTCs P0171 and P0174, proceed to that DTC before proceeding with this DTC. If no other DTCs are set, start engine and run to normal operating temperature. Ensure fuel system is in closed loop. Using scan tool, monitor short term and long term fuel trim for bank 1. If both parameters are not less than 95 on scan tool, go to step 4). If both parameters are less than 95 on scan tool, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0171 is set, go to next step. If DTC P0171 is not set, see DIAGNOSTIC AIDS.
If DTC P0174 is also set, go to next step. If DTC P0174 is not set, go to step 6).
Inspect vacuum hoses for splits, kinks and proper connections. Check throttle body and intake manifold for vacuum leaks. Check PCV valve operation and for system leaks. Inspect fuel system for contaminated fuel. Ensure ECM and sensor grounds are clean, tight and in correct locations. Inspect air induction system after MAF sensor for air leaks. Inspect engine for mechanical failure. Repair components as necessary, then to go step 7). If all components are okay, diagnose fuel system malfunction. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING article.
Inspect bank 1 for exhaust leaks, and for missing or loose exhaust hardware. Ensure bank 1 HO2S sensor 1 is installed securely and electrical connector is not contacting exhaust system or ignition wires. Check for vacuum leaks which only affect bank 1 (intake manifold, injector "O" rings). Inspect for engine mechanical failure. Repair components as necessary. After repairs, go to next step. If all components are okay, diagnose fuel system malfunction. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING article.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0171 is set, go to step 2). If DTC P0171 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

If DTC P0171 cannot be duplicated, DTC may have been caused by customer running vehicle out of fuel. Fuel system will be lean if pressure is too low. It may be necessary to monitor fuel pressure while driving vehicle at various speeds and/or loads to confirm this condition. Inspect for water in fuel system. Water, even in small amounts, near in-tank fuel pump inlet, can be delivered to injector. Water causes a lean exhaust and can set this DTC.

DTC P0172 - FUEL TRIM SYSTEM RICH, BANK 1

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions required to set DTC are

ECM detects fuel trim values less than -550 milliseconds for additive fuel trim or less than -21 percent for multiplicative fuel trim.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
If any other DTCs are set, except DTCs P0172 and P0175, proceed to that DTC before proceeding with this DTC. If no other DTCs are set, start engine and run to normal operating temperature. Ensure fuel system is in closed loop. Using scan tool, monitor short term and long term fuel trim for bank 1. If both parameters are not less negative than -95 on scan tool, go to step 4). If both parameters are less negative than -95 on scan tool, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0172 is set, go to next step. If DTC P0172 is not set, see DIAGNOSTIC AIDS.
If DTC P0175 is also set, go to next step. If DTC P0175 is not set, go to step 6).
Inspect for collapsed air intake duct. Ensure air filter is clean and not restricted. Ensure MAF sensor is installed in proper direction and no foreign objects are blocking inlet screen. Inspect for fuel in fuel pressure regulator hose. Repair components as necessary, then to go step 8). If all components are okay, diagnose fuel system malfunction. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING article.
Inspect fuel injectors for bank 1 leaks. Repair as necessary. After repairs, go to step 8). If injectors are okay, go to next step.
Replace faulty HO2S. After replacing sensor, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0172 is set, go to step 2). If DTC P0172 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Condition is intermittent. See TESTS W/O CODES article for diagnosis.

DTC P0174 - FUEL TRIM SYSTEM LEAN, BANK 2

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions for setting DTC

ECM detects fuel trim values greater than 550 milliseconds for additive fuel trim or greater than 23 percent for multiplicative fuel trim.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
If any other DTCs are set, except DTCs P0171 and P0174, proceed to that DTC before proceeding with this DTC. If no other DTCs are set, warm engine to normal operating temperature. Ensure fuel system is in closed loop. Using scan tool, monitor short term and long term fuel trim for bank 2. If both parameters are 95 on scan tool, go to step 4). If both parameters are not 95 on scan tool, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0174 is set, go to next step. If DTC P0174 is not set, see DIAGNOSTIC AIDS.
If DTC P0171 is also set, go to next step. If DTC P0171 is not set, go to step 6).
Inspect for collapsed air intake duct. Ensure air filter is clean and not restricted. Ensure MAF sensor is installed in proper direction and no foreign objects are blocking inlet screen. Inspect for fuel in fuel pressure regulator hose. Repair components as necessary. After repairs are complete, go step 7). If all components are okay, diagnose fuel system malfunction. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING article.
Inspect bank 2 for exhaust or vacuum leaks, or bank 2 HO2S 1 for proper installation. Repair as necessary. After repairs, go to next step. If no problems are found, diagnose fuel system. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING article.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0174 is set, go to step 2). If DTC P0174 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

If DTC P0174 cannot be duplicated, vehicle must have run out of fuel. Check for low fuel pressure, causing lean condition. Check for water contamination. See TESTS W/O CODES article for diagnosis.

DTC P0175 - FUEL TRIM SYSTEM RICH, BANK 2

Note. For circuit reference, see WIRING DIAGRAMS article.

To provide best possible combination of driveability, fuel economy and emission control, a closed loop air/fuel metering system is used. While in closed loop, ECM monitors heated oxygen sensor signal voltage and adjusts fuel delivery based on signal voltage. A change made in fuel delivery will be indicated by long and short term fuel trim values. Short term fuel trim values change rapidly in response to HO2S signal voltages. These changes fine tune engine fueling.

Conditions required to set DTC are

ECM detects fuel trim values less than -550 milliseconds for additive fuel trim or less than -23 percent for multiplicative fuel trim.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
If any other DTCs are set, except DTCs P0172 and P0175, proceed to that DTC before proceeding with this DTC. If no other DTCs are set, warm engine to normal operating temperature. Ensure fuel system is in closed loop. Using scan tool, monitor short term and long term fuel trim for bank 2. If both parameters are -95 on scan tool, go to step 4). If both parameters are not -95 on scan tool, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0175 is set, go to next step. If DTC P0175 is not set, see DIAGNOSTIC AIDS.
If DTC P0172 is also set, go to next step. If DTC P0172 is not set, go to step 6).
Inspect for collapsed air intake duct. Ensure air filter is clean and not restricted. Ensure MAF sensor is installed in proper direction and no foreign objects are blocking inlet screen. Inspect for fuel in fuel pressure regulator hose. Repair components as necessary. After repairs are complete, go step 8). If all components are okay, diagnose fuel system malfunction. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING article.
Inspect bank 2 for leaks. Repair as necessary. After repairs are complete, go to step 8). If no problems are found, go to next step.
Replace faulty HO2S. After replacing sensor, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0172 is set, go to step 2). If DTC P0172 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Problem is intermittent. See TESTS W/O CODES article for diagnosis.

DTC P0201 - INJECTOR NO. 1 CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

ECM will enable an injector on intake stroke of each cylinder. Ignition voltage is supplied directly to fuel injectors. ECM controls each injector by grounding control circuit via an internal driver.

Primary function of driver is to supply ground for component being controlled. Each driver has a fault line which is monitored by ECM. When ECM is commanding a component on, voltage of control circuit should be low (near zero). When ECM is commanding control circuit to component off, voltage potential of circuit should be high (near battery voltage). If fault detection circuit senses a voltage other than what is expected, this DTC will set.

ECM will monitor injector circuit for short to ground, short to voltage, open circuit or an internally shorted or excessively low resistance at injector. If ECM detects any of these malfunctions, this DTC will set and affected driver will be disabled. ECM will continue to test circuit and if fault disappears, driver will be reactivated.

Conditions required to set DTC are

Ignition voltage is 9-17 volts.
Engine speed greater than 80 RPM.
An injector circuit fault is detected.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and idle engine. Using scan tool, monitor misfire current cylinder No. 1. If counter is increasing, go to next step. If counter is not increasing, see DIAGNOSTIC AIDS.
Turn ignition off. Disconnect main fuel injector connector. Turn ignition on, with engine off. Using test light connected to battery voltage, probe injector No. 1 harness connector control circuit (ECM side). If test light is on, go to next step. If test light is off, go to step 6).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. If test light is on, go to step 11). If test light is off, go to next step.
Turn ignition on, with engine off. Using test light connected to ground, probe injector No. 1 harness connector control circuit (ECM side). If test light is on, go to step 12). If test light is off, go to step 15).
Crank engine. If test light blinks about once per second, go to step 8). If test light does not blink about once per second, go to next step.
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check harness continuity of injector No. 1 control circuit between main injector and ECM harness connectors. If continuity is present, go to step 14). If continuity is not present, go to step 10).
Turn ignition off. Using a jumper wire, reconnect switched battery feed circuit in male half of main injector harness connector to switched battery feed circuit in female half of main injector harness connector. Using test light connected to ground, probe injector No. 1 harness connector control circuit (injector side). Turn ignition on, with engine off. If test light is on, go to step 13). If test light is off, go to next step.
Check for poor connections and terminal tension at fuel injector harness connector or at main injector harness connector. Check injector control circuit for open, short to ground, or short to voltage between injector and main injector connector. Check for open in switched battery feed circuit between injector and wiring splice. Repair as necessary. After repairs are complete, go to step 16). If connections, terminals and circuits are okay, go to step 13).
Repair open or high resistance in injector control circuit. After repairs, go to step 16).
Repair short to ground in injector control circuit. After repairs, go to step 16).
Repair short to voltage in injector driver circuit. After repairs, go to step 16).
Replace fuel injector. After replacing injector, go to step 16).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 16). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0201 is set, go to step 2). If DTC P0201 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for poor connections at ECM or at component. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connection.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault.

DTC P0202 - INJECTOR NO. 2 CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

ECM will enable an injector on intake stroke of each cylinder. Ignition voltage is supplied directly to fuel injectors. ECM controls each injector by grounding control circuit via an internal driver.

Conditions required to set DTC are

An injector circuit fault is detected.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and idle engine. Using scan tool, monitor misfire current cylinder No. 2. If counter is increasing, go to next step. If counter is not increasing, see DIAGNOSTIC AIDS.
Turn ignition off. Disconnect main fuel injector connector. Turn ignition on, with engine off. Using test light connected to battery voltage, probe injector No. 2 harness connector control circuit (ECM side). If test light is on, go to next step. If test light is off, go to step 6).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. If test light is on, go to step 11). If test light is off, go to next step.
Turn ignition on, with engine off. Using test light connected to ground, probe injector No. 2 harness connector control circuit (ECM side). If test light is on, go to step 12). If test light is off, go to step 15).
Crank engine. If test light blinks about once per second, go to step 8). If test light does not blink about once per second, go to next step.
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check harness continuity of injector No. 2 control circuit between main injector and ECM harness connectors. If continuity is present, go to step 14). If continuity is not present, go to step 10).
Turn ignition off. Using a jumper wire, reconnect switched battery feed circuit in male half of main injector harness connector to switched battery feed circuit in female half of main injector harness connector. Using test light connected to ground, probe injector No. 2 harness connector control circuit (injector side). Turn ignition on, with engine off. If test light is on, go to step 13). If test light is off, go to next step.
Check for poor connections and terminal tension at fuel injector harness connector or at main injector harness connector. Check injector control circuit for open, short to ground, or short to voltage between injector and main injector connector. Check for open in switched battery feed circuit between injector and wiring splice. Repair as necessary. After repairs are complete, go to step 16). If connections, terminals and circuits are okay, go to step 13).
Repair open or high resistance in injector control circuit. After repairs, go to step 16).
Repair short to ground in injector control circuit. After repairs, go to step 16).
Repair short to voltage in injector driver circuit. After repairs, go to step 16).
Replace fuel injector. After replacing injector, go to step 16).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 16). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0202 is set, go to step 2). If DTC P0202 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault.

DTC P0203 - INJECTOR NO. 3 CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

ECM will enable an injector on intake stroke of each cylinder. Ignition voltage is supplied directly to fuel injectors. ECM controls each injector by grounding control circuit via an internal driver.

Conditions for setting DTC

An injector circuit fault is detected.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and idle engine. Using scan tool, monitor misfire current cylinder No. 3. If counter is increasing, go to next step. If counter is not increasing, see DIAGNOSTIC AIDS.
Turn ignition off. Disconnect main fuel injector connector. Turn ignition on, with engine off. Using test light connected to battery voltage, probe injector No. 3 harness connector control circuit (ECM side). If test light is on, go to next step. If test light is off, go to step 6).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. If test light is on, go to step 11). If test light is off, go to next step.
Turn ignition on, with engine off. Using test light connected to ground, probe injector No. 3 harness connector control circuit (ECM side). If test light is on, go to step 12). If test light is off, go to step 15).
Crank engine. If test light blinks about once per second, go to step 8). If test light does not blink about once per second, go to next step.
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check harness continuity of injector No. 3 control circuit between main injector and ECM harness connectors. If continuity is present, go to step 14). If continuity is not present, go to step 10).
Turn ignition off. Using a jumper wire, reconnect switched battery feed circuit in male half of main injector harness connector to switched battery feed circuit in female half of main injector harness connector. Using test light connected to ground, probe injector No. 3 harness connector control circuit (injector side). Turn ignition on, with engine off. If test light is on, go to step 13). If test light is off, go to next step.
Check for poor connections and terminal tension at fuel injector harness connector or at main injector harness connector. Check injector control circuit for open, short to ground, or short to voltage between injector and main injector connector. Check for open in switched battery feed circuit between injector and wiring splice. Repair as necessary. After repairs are complete, go to step 16). If connections, terminals and circuits are okay, go to step 13).
Repair open or high resistance in injector control circuit. After repairs, go to step 16).
Repair short to ground in injector control circuit. After repairs, go to step 16).
Repair short to voltage in injector driver circuit. After repairs, go to step 16).
Replace fuel injector. After replacing injector, go to step 16).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 16). If connections and terminals are okay, go to next step.
Replace ECM. NEW ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0203 is set, go to step 2). If DTC P0203 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault.

DTC P0204 - INJECTOR NO. 4 CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

ECM will enable an injector on intake stroke of each cylinder. Ignition voltage is supplied directly to fuel injectors. ECM controls each injector by grounding control circuit via an internal driver.

Conditions for setting DTC

An injector circuit fault is detected.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and idle engine. Using scan tool, monitor misfire current cylinder No. 4. If counter is increasing, go to next step. If counter is not increasing, see DIAGNOSTIC AIDS.
Turn ignition off. Disconnect main fuel injector connector. Turn ignition on, with engine off. Using test light connected to battery voltage, probe injector No. 4 harness connector control circuit (ECM side). If test light is on, go to next step. If test light is off, go to step 6).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. If test light is on, go to step 11). If test light is off, go to next step.
Turn ignition on, with engine off. Using test light connected to ground, probe injector No. 4 harness connector control circuit (ECM side). If test light is on, go to step 12). If test light is off, go to step 15).
Crank engine. If test light blinks about once per second, go to step 8). If test light does not blink about once per second, go to next step.
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check harness continuity of injector No. 4 control circuit between main injector and ECM harness connectors. If continuity is present, go to step 14). If continuity is not present, go to step 10).
Turn ignition off. Using a jumper wire, reconnect switched battery feed circuit in male half of main injector harness connector to switched battery feed circuit in female half of main injector harness connector. Using test light connected to ground, probe injector No. 4 harness connector control circuit (injector side). Turn ignition on, with engine off. If test light is on, go to step 13). If test light is off, go to next step.
Check for poor connections and terminal tension at fuel injector harness connector or at main injector connector. Check injector control circuit for open, short to ground, or short to voltage between injector and main injector connector. Check for open in switched battery feed circuit between injector and wiring splice. Repair as necessary, and then go to step 16). If connections, terminals and circuits are okay, go to step 13).
Repair open or high resistance in injector control circuit. After repairs, go to step 16).
Repair short to ground in injector control circuit. After repairs, go to step 16).
Repair short to voltage in injector driver circuit. After repairs, go to step 16).
Replace fuel injector. After replacing injector, go to step 16).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 16). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0204 is set, go to step 2). If DTC P0204 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault.

DTC P0205 - INJECTOR NO. 5 CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

ECM will enable an injector on intake stroke of each cylinder. Ignition voltage is supplied directly to fuel injectors. ECM controls each injector by grounding control circuit via an internal driver.

Conditions required to set DTC are

An injector circuit fault is detected.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and idle engine. Using scan tool, monitor misfire current cylinder No. 5. If counter is increasing, go to next step. If counter is not increasing, see DIAGNOSTIC AIDS.
Turn ignition off. Disconnect main fuel injector connector. Turn ignition on, with engine off. Using test light connected to battery voltage, probe injector No. 5 harness connector control circuit (ECM side). If test light is on, go to next step. If test light is off, go to step 6).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. If test light is on, go to step 11). If test light is off, go to next step.
Turn ignition on, with engine off. Using test light connected to ground, probe injector No. 5 harness connector control circuit (ECM side). If test light is on, go to step 12). If test light is off, go to step 15).
Crank engine. If test light blinks about once per second, go to step 8). If test light does not blink about once per second, go to next step.
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check harness continuity of injector No. 5 control circuit between main injector and ECM harness connectors. If continuity is present, go to step 14). If continuity is not present, go to step 10).
Turn ignition off. Using a jumper wire, reconnect switched battery feed circuit in male half of main injector harness connector to switched battery feed circuit in female half of main injector harness connector. Using test light connected to ground, probe injector No. 5 harness connector control circuit (injector side). Turn ignition on, with engine off. If test light is on, go to step 13). If test light is off, go to next step.
Check for poor connections and terminal tension at fuel injector harness connector or at main injector connector. Check injector control circuit for open, short to ground, or short to voltage between injector and main injector connector. Check for open in switched battery feed circuit between injector and wiring splice. Repair as necessary, and then go to step 16). If connections, terminals and circuits are okay, go to step 13).
Repair open or high resistance in injector control circuit. After repairs, go to step 16).
Repair short to ground in injector control circuit. After repairs, go to step 16).
Repair short to voltage in injector driver circuit. After repairs, go to step 16).
Replace fuel injector. After replacing injector, go to step 16).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 16). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0205 is set, go to step 2). If DTC P0205 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault.

DTC P0206 - INJECTOR NO. 6 CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

ECM will enable an injector on intake stroke of each cylinder. Ignition voltage is supplied directly to fuel injectors. ECM controls each injector by grounding control circuit via an internal driver.

Conditions required to set DTC are

An injector circuit fault is detected.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and idle engine. Using scan tool, monitor misfire current cylinder No. 6. If counter is increasing, go to next step. If counter is not increasing, see DIAGNOSTIC AIDS.
Turn ignition off. Disconnect main fuel injector connector. Turn ignition on, with engine off. Using test light connected to battery voltage, probe injector No. 6 harness connector control circuit (ECM side). If test light is on, go to next step. If test light is off, go to step 6).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. If test light is on, go to step 11). If test light is off, go to next step.
Turn ignition on, with engine off. Using test light connected to ground, probe injector No. 6 harness connector control circuit (ECM side). If test light is on, go to step 12). If test light is off, go to step 15).
Crank engine. If test light blinks about once per second, go to step 8). If test light does not blink about once per second, go to next step.
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check harness continuity of injector No. 6 control circuit between main injector and ECM harness connectors. If continuity is present, go to step 14). If continuity is not present, go to step 10).
Turn ignition off. Using a jumper wire, reconnect switched battery feed circuit in male half of main injector harness connector to switched battery feed circuit in female half of main injector harness connector. Using test light connected to ground, probe injector No. 6 harness connector control circuit (injector side). Turn ignition on, with engine off. If test light is on, go to step 13). If test light is off, go to next step.
Check for poor connections and terminal tension at fuel injector harness connector or at main injector connector. Check injector control circuit for open, short to ground, or short to voltage between injector and main injector connector. Check for open in switched battery feed circuit between injector and wiring splice. Repair as necessary, and then go to step 16). If connections, terminals and circuits are okay, go to step 13).
Repair open or high resistance in injector control circuit. After repairs, go to step 16).
Repair short to ground in injector control circuit. After repairs, go to step 16).
Repair short to voltage in injector driver circuit. After repairs, go to step 16).
Replace fuel injector. After replacing injector, go to step 16).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 16). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0206 is set, go to step 2). If DTC P0206 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

For any test that requires probing ECM or component harness connectors, use Connector Test Adapter Kit (J-35616-A). This will prevent damage to harness connector terminals. Check for poor connections at ECM or at component. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connection.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault.

DTC P0230 - FUEL PUMP CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

Fuel pump relay coil is supplied power via main relay (switched battery feed). ECM controls relay by grounding control circuit via an internal driver.

When ECM detects reference pulses from Crankshaft Position (CKP) sensor, ECM will enable fuel pump. Relay is used to control high current flow to fuel pump. This allows ECM driver to only have to handle relatively low current used by relay.

Conditions for setting DTC

A short to ground, open, or short to battery voltage detected on control circuit.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition on, with engine off. Using scan tool, command fuel pump relay on and off. If relay turns on and off with each command, go to next step. If relay does not turn on and off with each command, go to step 5).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Jumper main relay control circuit to ground. Using DVOM on 10-amp scale, measure current between ground and relay control circuit at ECM harness connector, for 2 minutes. If current draw is 0.10-0.75 amp, see DIAGNOSTIC AIDS. If current draw is not 0.10-0.75 amp, go to next step.
Turn ignition off. Disconnect fuel pump relay connector. Using DVOM, measure resistance between ground and relay control circuit at ECM harness connector. If resistance is infinite, go to step 11). If resistance is not infinite, go to step 9).
Turn ignition off. Disconnect fuel pump relay connector. Connect test light between relay coil terminals at harness connector. Turn ignition on. Using scan tool, command fuel pump relay on and off. If test light turns on and off with each command, go to step 8). If test light does not turn on and off with each command, go to next step.
With test light connected to ground, probe relay harness connector switched battery feed circuit. If test light is on, go to next step. If test light is off, go to step 10).
Turn ignition off. Reconnect fuel pump relay. Disconnect ECM harness connector. Jumper main relay control circuit to ground. With fused jumper wire connected to ground, probe fuel pump relay control circuit at ECM harness connector. If relay operates, go to step 12). If relay does not operate, go to step 9).
Check for poor connections at relay. Repair as necessary. After repairs, go to step 14). If connections are okay, go to step 11).
Repair relay control circuit. After repairs, go to step 14).
Repair switched battery feed circuit to relay. After repairs, go to step 14).
Replace relay. After replacing relay, go to step 14).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 14). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0230 is set, go to step 2). If DTC P0230 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault.

DTC P0300 - ENGINE MISFIRE DETECTED

Note. For circuit reference, see WIRING DIAGRAMS article.

Crankshaft Position (CKP) sensor sends pulses to ECM as reluctor wheel teeth rotate past sensor. Besides using these pulses to synchronize ignition and fuel injector operation, ECM also times interval between each pulse and compares each new time interval with previous one to determine when an excessive change in crankshaft speed has occurred.

A misfire causes an unexpected change in crankshaft speed. A certain amount of acceleration/deceleration is expected between each firing stroke, but if crankshaft speed changes more than expected amount, ECM will interpret this as a misfire. ECM continuously calculates crankshaft position from CKP sensor signals.

This information is used to determine which cylinder is misfiring so ECM can increment appropriate misfire counter and set appropriate DTC, if necessary. If ECM is able to determine a specific cylinder is misfiring, DTC for that cylinder will set. If misfire is random and on multiple cylinders, DTC P0300 will set.

Conditions for setting DTC

Misfire greater than legislated limit (amount of misfire ranging from 1.0-12.5 percent.
Condition must be met for at least 5 camshaft revolutions.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
If DTCs P0201-P0206 are also set, go to applicable DTC. If DTCs P0201-P0206 are not present, go to next step.
If DTC P1460 is set, go to step 5). If DTC P1460 is not set, go to next step.
If DTCs P0301-P0306 are also set, go to applicable DTC. If DTCs P0301-P0306 are not present, go to step 8).
Using scan tool, monitor fuel level volts. If reading is greater than 6.8 volts, go to next step. If reading is less than 6.8 volts, go to step 8).
Add 5 gallons of fuel to fuel tank. If fuel level volts is less than 6.8 volts, go to step 14). If fuel level volts is greater than 6.8 volts, go to next step.
Repair fuel sending unit or circuit problem. After repairs, go to next step.
Start and idle engine. Using scan tool, monitor all misfire current counters (6 counters, one per cylinder). If any misfire current counters increase, go to next step. If any misfire current counters do not increase, go to step 10).
Inspect vacuum hoses for splits, kinks and proper connections. Check throttle body and intake manifold for vacuum leaks. Check PCV valve operation and system for vacuum leaks. Ensure ECM grounds are clean and secure. Ensure all injector harness connectors and spark plug wires are installed at correct locations and secure. Repair as necessary. After repairs, go to step 14). If all components and systems are okay, go to step 11).
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0300 is set, go to next step. If DTC P0300 is not set, see DIAGNOSTIC AIDS.
Using DVOM, check resistance of spark plug wires at cylinder(s) which indicate misfire. If resistance is greater than 10,000 ohms, replace wire(s) as necessary. After repairs, go to step 14). If spark plug wires are okay, go to next step.
Remove spark plug(s) as necessary and inspect for signs of oil or coolant fouling. Replace spark plug(s) or repair engine as necessary. If spark plugs are okay, go to next step.
Check spark plugs for cracks or damage, excessive wear or improper gap. Check for carbon tracking on insulator. Replace components as necessary. After repairs, go to next step. If components are okay, see DIAGNOSTIC AIDS.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0300 is set, go to step 2). If DTC P0300 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

If DTC P1430 was also set, and no misfire is currently present, vehicle may simply have been run low on fuel. This DTC being present with properly functioning fuel sending circuit eliminates need for a lengthy misfire diagnosis.

A misfire DTC could be caused by excessive vibration from sources other than engine. Possible sources could be an out of balance or out of round tire, out of round brake rotor or drum, drive shaft out of balance or rough road.

DTC P0301 - CYLINDER NO. 1 MISFIRE DETECTED

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions required to set DTC are

Misfire more than legislated limit (amount of misfire ranging from 1.0-12.5 percent.
Condition must be met for at least 5 camshaft revolutions.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and idle engine. Using scan tool, monitor misfire current counter for this cylinder. If misfire current counter increases, go to next step. If any misfire current counter does not increase, go to step 4).
Inspect vacuum hoses for splits, kinks and proper connections. Check throttle body and intake manifold for vacuum leaks. Check PCV valve operation and system for vacuum leaks. Ensure ECM grounds are clean and secure. Ensure all injector harness connectors and spark plug wires are installed at correct locations and secure. Repair as necessary. After repairs, go to step 8). If all components and systems are okay, go to step 5).
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0301 is set, go to next step. If DTC P0301 is not set, see DIAGNOSTIC AIDS.
Using Spark Plug Tester (J-26792), check spark at affected cylinder while cranking engine. If spark is present, go to next step. If spark is not present, diagnose ignition system. See BASIC IGNITION SYSTEM CHECKS in BASIC TESTING article.
Remove spark plug(s) as necessary and inspect for signs of oil or coolant fouling. Replace spark plug(s) or repair engine as necessary. If spark plugs are okay, go to next step.
Check spark plugs for cracks or damage, excessive wear or improper gap. Check for carbon tracking on insulator. Replace components as necessary. After repairs, go step 9). If components are okay, go to next step.
Check compression and perform leak down test on affected cylinder. Replace components as necessary, then go to next step. If components are okay, diagnose fuel system malfunction. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING article.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0301 is set, go to step 2). If DTC P0301 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

DTC P0302 - CYLINDER NO. 2 MISFIRE DETECTED

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions for setting DTC

Misfire more than legislated limit (amount of misfire ranging from 1.0-12.5 percent.
Condition must be met for at least 5 camshaft revolutions.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and idle engine. Using scan tool, monitor misfire current counter for this cylinder. If misfire current counter increases, go to next step. If any misfire current counter does not increase, go to step 4).
Inspect vacuum hoses for splits, kinks and proper connections. Check throttle body and intake manifold for vacuum leaks. Check PCV valve operation and PCV system for vacuum leaks. Ensure ECM grounds are clean and secure. Ensure all injector harness connectors and spark plug wires are installed at correct locations and secure. Repair or replace as necessary. After repairs are complete, go to step 8). If all components and systems are okay, go to step 5).
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0302 is set, go to next step. If DTC P0302 is not set, see DIAGNOSTIC AIDS.
Using Spark Plug Tester (J-26792), check spark at affected cylinder while cranking engine. If spark is present, go to next step. If spark is not present, diagnose ignition system. See BASIC IGNITION SYSTEM CHECKS in BASIC TESTING article.
Remove spark plug(s) as necessary and inspect for signs of oil or coolant fouling. Replace spark plug(s) or repair engine as necessary. If spark plugs are okay, go to next step.
Check spark plugs for cracks or damage, excessive wear or improper gap. Check for carbon tracking on insulator. Replace components as necessary. After repairs, go step 9). If components are okay, go to next step.
Check compression and perform leak down test on affected cylinder. Replace components as necessary. After repairs, go to next step. If components are okay, diagnose fuel system malfunction. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING article.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0302 is set, repeat step 2). If DTC P0302 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

DTC P0303 - CYLINDER NO. 3 MISFIRE DETECTED

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions for setting DTC

Misfire more than legislated limit (amount of misfire ranging from 1.0-12.5 percent.
Condition must be met for at least 5 camshaft revolutions.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and idle engine. Using scan tool, monitor misfire current counter for this cylinder. If misfire current counter increases, go to next step. If any misfire current counter does not increase, go to step 4).
Inspect vacuum hoses for splits, kinks and proper connections. Check throttle body and intake manifold for vacuum leaks. Check PCV valve operation and system for vacuum leaks. Ensure ECM grounds are clean and secure. Ensure all injector harness connectors and spark plug wires are installed at correct locations and secure. Repair as necessary. After repairs are complete, go to step 8). If all components and systems are okay, go to step 5).
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0303 is set, go to next step. If DTC P0303 is not set, see DIAGNOSTIC AIDS.
Using Spark Plug Tester (J-26792), check spark at affected cylinder while cranking engine. If spark is present, go to next step. If spark is not present, diagnose ignition system. See BASIC IGNITION SYSTEM CHECKS in BASIC TESTING article.
Remove spark plug(s) as necessary and inspect for signs of oil or coolant fouling. Replace spark plug(s) or repair engine as necessary. If spark plugs are okay, go to next step.
Check spark plugs for cracks or damage, excessive wear or improper gap. Check for carbon tracking on insulator. Replace components as necessary. After repairs, go to step 9). If components are okay, go to next step.
Check compression and perform leak down test on affected cylinder. Replace components as necessary. After repairs, go to next step. If components are okay, diagnose fuel system malfunction. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING article.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0303 is set, go to step 2). If DTC P0303 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

DTC P0304 - CYLINDER NO. 4 MISFIRE DETECTED

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions for setting DTC

Misfire more than legislated limit (amount of misfire ranging from 1.0-12.5 percent.
Condition must be met for at least 5 camshaft revolutions.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and idle engine. Using scan tool, monitor misfire current counter for this cylinder. If misfire current counter increases, go to next step. If any misfire current counter does not increase, go to step 4).
Inspect vacuum hoses for splits, kinks and proper connections. Check throttle body and intake manifold for vacuum leaks. Check PCV valve operation and PCV system for vacuum leaks. Ensure ECM grounds are clean and secure. Ensure all injector harness connectors and spark plug wires are installed at correct locations and secure. Repair or replace as necessary. After repairs are complete, go to step 8). If all components and systems are okay, go to step 5).
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0304 is set, go to next step. If DTC P0304 is not set, see DIAGNOSTIC AIDS.
Using Spark Plug Tester (J-26792), check spark at affected cylinder while cranking engine. If spark is present, go to next step. If spark is not present, diagnose ignition system. See BASIC IGNITION SYSTEM CHECKS in BASIC TESTING article.
Remove spark plug(s) as necessary and inspect for signs of oil or coolant fouling. Replace spark plug(s) or repair engine as necessary. If spark plugs are okay, go to next step.
Check spark plugs for cracks or damage, excessive wear or improper gap. Check for carbon tracking on insulator. Replace components as necessary. After repairs, go step 9). If components are okay, go to next step.
Check compression and perform leak down test on affected cylinder. Replace components as necessary. After repairs, go to next step. If components are okay, diagnose fuel system malfunction. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING article.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0304 is set, go to step 2). If DTC P0304 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

DTC P0305 - CYLINDER NO. 5 MISFIRE DETECTED

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions for setting DTC

Misfire more than legislated limit (amount of misfire ranging from 1.0-12.5 percent.
Condition must be met for at least 5 camshaft revolutions.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and idle engine. Using scan tool, monitor misfire current counter for this cylinder. If misfire current counter increases, go to next step. If any misfire current counter does not increase, go to step 4).
Inspect vacuum hoses for splits, kinks and proper connections. Check throttle body and intake manifold for vacuum leaks. Check PCV valve operation and PCV system for vacuum leaks. Ensure ECM grounds are clean and secure. Ensure all injector harness connectors and spark plug wires are installed at correct locations and secure. Repair or replace as necessary. After repairs are complete, go to step 8). If all components and systems are okay, go to step 5).
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0305 is set, go to next step. If DTC P0305 is not set, see DIAGNOSTIC AIDS.
Using Spark Plug Tester (J-26792), check spark at affected cylinder while cranking engine. If spark is present, go to next step. If spark is not present, diagnose ignition system. See BASIC IGNITION SYSTEM CHECKS in BASIC TESTING article.
Remove spark plug(s) as necessary and inspect for signs of oil or coolant fouling. Replace spark plug(s) or repair engine as necessary. If spark plugs are okay, go to next step.
Check spark plugs for cracks or damage, excessive wear or improper gap. Check for carbon tracking on insulator. Replace components as necessary. After repairs, go step 9). If components are okay, go to next step.
Check compression and perform leak down test on affected cylinder. Replace components as necessary. After repairs, go to next step. If components are okay, diagnose fuel system malfunction. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING article.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0305 is set, go to step 2). If DTC P0305 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

DTC P0306 - CYLINDER NO. 6 MISFIRE DETECTED

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions for setting DTC

Misfire more than legislated limit (amount of misfire ranging from 1.0-12.5 percent.
Condition must be met for at least 5 camshaft revolutions.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start and idle engine. Using scan tool, monitor misfire current counter for this cylinder. If misfire current counter increases, go to next step. If any misfire current counter does not increase, go to step 4).
Inspect vacuum hoses for splits, kinks and proper connections. Check throttle body and intake manifold for vacuum leaks. Check PCV valve operation and PCV system for vacuum leaks. Ensure ECM grounds are clean and secure. Ensure all injector harness connectors and spark plug wires are installed at correct locations and secure. Repair or replace as necessary. After repairs are complete, go to step 8). If all components and systems are okay, go to step 5).
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0306 is set, go to next step. If DTC P0306 is not set, see DIAGNOSTIC AIDS.
Using Spark Plug Tester (J-26792), check spark at affected cylinder while cranking engine. If spark is present, go to next step. If spark is not present, diagnose ignition system. See BASIC IGNITION SYSTEM CHECKS in BASIC TESTING article.
Remove spark plug(s) as necessary and inspect for signs of oil or coolant fouling. Replace spark plug(s) or repair engine as necessary. If spark plugs are okay, go to next step.
Check spark plugs for cracks or damage, excessive wear or improper gap. Check for carbon tracking on insulator. Replace components as necessary. After repairs, go step 9). If components are okay, go to next step.
Check compression and perform leak down test on affected cylinder. Replace components as necessary. After repairs, go to next step. If components are okay, diagnose fuel system malfunction. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING article.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0306 is set, go to step 2). If DTC P0306 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

DTC P0325 - KNOCK SENSOR CIRCUIT BANK 1

Note. For circuit reference, see WIRING DIAGRAMS article.

Knock Sensor (KS) system is used to detect engine detonation. ECM will retard spark timing based on signals from KS module. Knock sensors produce an AC voltage signal that is sent to KS module. Amount of AC voltage signal produced is proportional to amount of knock.

An operating engine produces a normal amount of engine mechanical vibration (noise). Knock sensors will produce an AC voltage signal from this noise. When an engine is operating, ECM will learn minimum and maximum frequency of noise the engine produces. When ECM determines that this frequency is less than or greater than expected amount, a knock sensor DTC will set.

Conditions for setting DTC

Knock sensor signal is lower than values listed in KNOCK SENSOR SPECIFICATIONS table.

Engine Speed (RPM)	Reference Signal (mV)
0	1.83
800	2.44
1600	3.66
2000	4.27
2400	5.49
2800	6.71
3200	8.54
3600	10.38
4000	12.82
4400	15.26
4800	18.31
5200	22.58
5600	28.69
5920	39.06
6200	39.06
6400	39.06

KNOCK SENSOR SPECIFICATIONS

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step. NOTE: If engine knock can be heard, repair engine mechanical problem before proceeding with this DTC.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate at greater than 2000 RPM and as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0325 is set, go to next step. If DTC P0325 is not set, see DIAGNOSTIC AIDS.
Turn ignition off. Disconnect knock sensor connector. Disconnect ECM connector located in engine compartment relay center. Check for poor connections or terminal tension at ECM and knock sensor connectors. Repair as necessary. After repairs, go to step 14). If connections and terminals are okay, go to next step.
Turn ignition on, with engine off. Using DVOM, measure voltage between ground and KS signal circuit at ECM harness connector. If any voltage is present, go to step 9). If no voltage is present, go to next step.
Using DVOM, check harness continuity of KS signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 11).
Using DVOM, check harness continuity between ground and KS sensor signal circuit. If continuity is present, go to step 10). If continuity is not present, go to next step.
Turn ignition off. Reconnect ECM connector. Turn ignition on, with engine off. Using test light connected to battery voltage, probe KS harness connector ground circuit. If test light is on, go to next step. If test light is off, go to step 12).
Using test light connected to battery voltage, probe KS sensor shielding on wiring harness. If test light is on, see DIAGNOSTIC AIDS. If test light is off, go to step 13).
Repair short to voltage is signal circuit. After repairs, go to step 14).
Repair short to ground in signal circuit. After repairs, go to step 14).
Repair open or high resistance in signal circuit. After repairs, go to step 14).
Repair open or high resistance in ground circuit. After repairs, go to step 14).
Repair knock sensor shield circuit. After repairs, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate at greater than 2000 RPM and as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0325 is set, repeat step 2). If DTC P0325 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault. If sensor signal is only affected when harness is moved at component, and there is no problem with harness or connections, component may be faulty.

Check knock sensor for proper installation. A knock sensor that is loose or over tightened may cause this DTC to set.

DTC P0330 - KNOCK SENSOR CIRCUIT BANK 2

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions required to set DTC are

Knock sensor signal is lower than values listed in KNOCK SENSOR SPECIFICATIONS table.

Engine Speed (RPM)	Reference Signal (mV)
0	1.83
800	2.44
1600	3.66
2000	4.27
2400	5.49
2800	6.71
3200	8.54
3600	10.38
4000	12.82
4400	15.26
4800	18.31
5200	22.58
5600	28.69
5920	39.06
6200	39.06
6400	39.06

KNOCK SENSOR SPECIFICATIONS

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step. NOTE: If engine knock can be heard, repair engine mechanical problem before proceeding with this DTC.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate at greater than 2000 RPM and as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0330 is set, go to next step. If DTC P0330 is not set, see DIAGNOSTIC AIDS.
Turn ignition off. Disconnect knock sensor connector. Disconnect ECM connector located in engine compartment relay center. Check for poor connections and terminal tension at ECM and knock sensor connectors. Repair as necessary. After repairs, go to step 14). If connections and terminals are okay, go to next step.
Turn ignition on, with engine off. Using DVOM, measure voltage between ground and KS signal circuit at ECM harness connector. If any voltage is present, go to step 9). If no voltage is present, go to next step.
Using DVOM, check harness continuity of KS signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 11).
Using DVOM, check harness continuity between ground and KS sensor signal circuit. If continuity is present, go to step 10). If continuity is not present, go to next step.
Turn ignition off. Reconnect ECM connector. Turn ignition on, with engine off. Using test light connected to battery voltage, probe KS harness connector ground circuit. If test light is on, go to next step. If test light is off, go to step 12).
Using test light connected to battery voltage, probe KS sensor shielding on wiring harness. If test light is on, see DIAGNOSTIC AIDS. If test light is off, go to step 13).
Repair short to voltage is signal circuit. After repairs, go to step 14).
Repair short to ground in signal circuit. After repairs, go to step 14).
Repair open or high resistance in signal circuit. After repairs, go to step 14).
Repair open or high resistance in ground circuit. After repairs, go to step 14).
Repair knock sensor shield circuit. After repairs, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate at greater than 2000 RPM and as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0330 is set, go to step 2). If DTC P0330 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for misrouted wiring harness. Inspect harness to ensure that it is not routed too close to high voltage wires (spark plug wires) or too close to high current devices (alternator, motors, solenoids).

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault. If sensor signal is only affected when harness is moved at component, and there is no problem with harness or connections, component may be faulty.

Check knock sensor for proper installation. A knock sensor that is loose or over tightened may cause this DTC to set.

DTC P0335 - CRANKSHAFT POSITION SENSOR CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

Crankshaft Position (CKP) sensor works in conjunction with a 58-tooth reluctor wheel on crankshaft. ECM pulls CKP sensor signal circuit low and monitors voltage on circuit. As each reluctor wheel tooth rotates past sensor, sensor's internal circuitry causes voltage to be applied to signal circuit, creating a square wave signal used by ECM. Reluctor wheel teeth are 6 degrees apart. Having only 58 teeth leaves a 12-degree span that is uncut. This creates a signature pattern that enables ECM to determine crankshaft position.

ECM can determine which 2 cylinders are approaching top dead center based on CKP signal alone. Camshaft Position (CMP) sensor signal is then used to determine which 2 cylinders are on firing stroke. ECM can then properly synchronize ignition system, fuel injectors and knock control. This sensor is also used to detect misfire. Refer to DTC P0300 for misfire detection.

Conditions required to set DTC are

ECM has detected no CKP sensor pulses.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Attempt to start engine. If engine starts and runs, problem is intermittent. See DIAGNOSTIC AIDS. If engine does not start, go to next step.
Turn ignition off. Disconnect CKP sensor connector. Turn ignition on, with engine off. Using DVOM, measure voltage between ground and CKP sensor harness connector signal circuit (ECM side). If voltage is 0.5-1.5 volts, go to step 6). If voltage is not 0.5-1.5 volts, go to next step.
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check harness continuity of CKP sensor signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 10).
Using DVOM, check harness continuity between ground and CKP sensor signal circuit. If continuity is present, go to step 9). If continuity is not present, go to step 14).
Using test light connected to battery voltage, probe CKP sensor harness connector ground circuit (ECM side). If test light is on, go to step 8). If test light is off, go to next step.
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check harness continuity of CKP sensor ground circuit. If continuity is present, go to step 14). If continuity is not present, go to step 11).
Disconnect main fuel injector connector. Connect Signal Generator Tester (J-33431-B) to CKP sensor harness connector (ECM side). Using scan tool, monitor engine RPM. If RPM is indicated on scan tool, go to step 12). If RPM is not indicated on scan tool, go to step 15).
Repair short to ground in signal circuit. After repairs, go to step 16).
Repair open or high resistance in signal circuit. After repairs, go to step 16).
Repair open or high resistance in ground circuit. After repairs, go to step 16).
Check for poor connection and terminal tension at CKP sensor connector. Check sensor for proper installation. A sensor that is loose or not fully seated could cause an excessive air gap between sensor and reluctor wheel. Repair as necessary. After repairs, go to step 16). If connections and terminals are okay, go to next step.
Replace CKP sensor. After replacing sensor, go to step 16).
Check for poor connections and terminal tension at ECM connectors. Repair as necessary. After repairs, go to step 16). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0335 is set, go to step 2). If DTC P0335 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault. If sensor signal is only affected when harness is moved at component, and there is no problem with harness or connections, component may be faulty.

Check CKP sensor for proper installation. A sensor that is loose or not fully seated, causing an excessive air gap between sensor and reluctor wheel, may cause this DTC to set.

DTC P0336 - CRANKSHAFT POSITION SENSOR SYSTEM PERFORMANCE

Note. For circuit reference, see WIRING DIAGRAMS article.

ECM can determine which 2 cylinders are approaching top dead center based on CKP signal alone. Camshaft Position (CMP) sensor signal is used to determine which 2 cylinders are on firing stroke. ECM can then properly synchronize ignition system, fuel injectors and knock control. This sensor is also used to detect misfire. Refer to DTC P0300 for misfire detection.

Conditions for setting DTC

Reluctor wheel gap is out of range.
More than 58 teeth were counted before signature tooth.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate at greater than 500 RPM and as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0336 is set, go to next step. If DTC P0336 is not set, see DIAGNOSTIC AIDS.
Using test light connected to battery voltage, probe CKP sensor shielding on wiring harness. If test light is on, go to next step. If test light is off, go to step 5).
Check for poor connection and terminal tension at CKP sensor and ECM harness connectors. Check sensor for proper installation. A sensor that is loose or not fully seated could cause an excessive air gap between sensor and reluctor wheel. Check for loose or damaged crankshaft reluctor wheel. Ensure CKP sensor is not touching reluctor wheel. Repair as necessary. After repairs, go to step 7). If connections, terminals and components are okay, go to step 6).
Repair CKP shield circuit. After repairs, go to step 7).
Replace CKP sensor. After replacing sensor, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate at greater than 500 RPM. Check for DTCs. If DTC P0336 is set, go to step 2). If DTC P0336 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault. If sensor signal is only affected when harness is moved at component, and there is no problem with harness or connections, component may be faulty.

Check CKP sensor for proper installation. A sensor that is loose or not fully seated, causing an excessive air gap between sensor and reluctor wheel, may cause this DTC to set.

DTC P0340 - CAMSHAFT POSITION SENSOR CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

Camshaft Position (CMP) sensor works in conjunction with a single-tooth reluctor wheel on bank 2 intake camshaft. ECM increases CMP sensor signal circuit to 12 volts and monitors this voltage. As reluctor wheel tooth rotates past sensor, sensor's internal circuitry pulls signal circuit to ground, creating a square wave signal used by ECM. Reluctor wheel tooth covers 180 degrees of camshaft circumference.

This causes CMP signal voltage to transition once per crankshaft revolution. This signal, when combined with CKP sensor signal, enables ECM to determine exactly which cylinder is on firing stroke. ECM can then properly synchronize ignition system, fuel injectors and knock control. Note that as long as CKP sensor signal is available, engine can start even if there is no CMP sensor signal. ECM will default to non-sequential fuel injection operation.

Conditions required to set DTC are

CMP signal is incorrect for at least 500 milliseconds.
Engine has completed at least 100 revolutions.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start engine. Using scan tool, monitor Cam Signal Present. If scan tool indicates HIGH RANDOMLY, problem is intermittent. See DIAGNOSTIC AIDS. If scan tool does not indicate HIGH RANDOMLY, go to next step.
Turn ignition off. Disconnect CMP sensor connector. Turn ignition on, with engine off. Using DVOM, measure voltage between ground and CMP sensor harness connector switched battery feed circuit (ECM side). If battery voltage is present, go to next step. If battery voltage is not present, go to step 10).
Using DVOM, measure voltage between ground and CMP sensor harness connector signal circuit (ECM side). If battery voltage is present, go to step 7). If battery voltage is not present, go to next step.
Turn ignition off. Disconnect ECM connector located in engine compartment, in relay center. Using DVOM, check harness continuity of CMP sensor signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 12).
Using DVOM, check harness continuity between ground and CMP sensor signal circuit. If continuity is present, go to step 11). If continuity is not present, go to step 16).
Using test light connected to battery voltage, probe CMP sensor harness connector ground circuit (ECM side). If test light is on, go to step 9). If test light is off, go to next step.
Turn ignition off. Disconnect ECM connector located in engine compartment relay center. Using DVOM, check harness continuity of CMP sensor harness connector ground circuit. If continuity is present, go to step 16). If continuity is not present, go to step 13).
Connect Signal Generator Tester (J-33431-B) to CMP sensor harness connector (ECM side). Turn ignition on. Turn tester on and set to generate a 54 MPH signal. Using scan tool, monitor Cam Signal Present. If scan tool indicates HIGH RANDOMLY, go to step 14). If scan tool does not indicate HIGH RANDOMLY, go to step 16).
Repair switched battery feed circuit. After repairs, go to step 18).
Repair short to ground in signal circuit. After repairs, go to step 18).
Repair open or high resistance in signal circuit. After repairs, go to step 18).
Repair open or high resistance in ground circuit. After repairs, go to step 18).
Check for poor connection and terminal tension at CMP sensor harness connector. Check CMP sensor for proper installation. A sensor that is loose or not fully seated could cause an excessive air gap between CMP sensor and reluctor wheel. Repair as necessary. After repairs, go to step 18). If connections and terminals are okay, go to next step.
Replace CKP sensor. After replacing sensor, go to step 18).
Check for poor connection and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 18). If connections and terminals are okay, go to next step.
Replace ECM. NEW ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0340 is set, go to step 2). If DTC P0340 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault. If sensor signal is only affected when harness is moved at component, and there is no problem with harness or connections, component may be faulty.

Check CMP sensor for proper installation. A sensor that is loose or not fully seated, causing an excessive air gap between sensor and reluctor wheel, may cause this DTC to set.

DTC P0410 - AIR SYSTEM CONSTANT FLOW DETECTED

Note. For circuit reference, see WIRING DIAGRAMS article.

Secondary Air Injection (AIR) system reduces hydrocarbons, carbon monoxide and oxides of nitrogen exhaust emissions. When engine is started, ECM commands AIR pump relay and AIR solenoid valve on, injecting clean air into engine exhaust ports. ECM switches AIR system off when oxygen sensors become active. Airflow is controlled by vacuum operated cutoff valve. Vacuum to valve is controlled by AIR solenoid valve. A check valve close to engine prevents hot exhaust gasses from backing up into AIR system.

ECM uses short term fuel trim to diagnose AIR system. When AIR system is enabled, ECM monitors short term fuel trim. If short term fuel trim goes below a threshold, ECM interprets this as an indication that AIR system is operational. When AIR pump is disabled, short term fuel trim should return to normal.

Conditions required to set DTC are

Short term fuel trim remains below a predetermined value for at least 20 seconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start engine. Allow engine to enter closed loop operation. Using scan tool, command AIR pump relay on and off. If AIR pump turns on and off, go to step 6). If AIR pump does not turn on and off, go to next step.
Remove AIR pump relay. If AIR pump is off, go to next step. If AIR pump is on, go to step 9).
Using test light connected to battery voltage, probe relay control circuit. Using scan tool, command AIR pump relay on and off. If test light turns on and off, go to step 11). If test light does not turn on and off, go to next step.
Turn ignition off. Disconnect ECM connector located in engine compartment, in relay center. Using test light connected to battery voltage, probe relay control circuit. If test light is on, go to step 10). If test light is off, go to step 14).
Remove AIR cutoff valve. Attempt to blow through cutoff valve. If valve is stuck open, go to step 13). If valve is not stuck open, go to next step.
Disconnect vacuum hose at actuator. Using scan tool, command AIR solenoid valve on and off. If vacuum is present when solenoid valve is off, go to step 12). If vacuum is not present when solenoid valve is off, go to next step.
Check for loose or disconnected AIR hoses and pipes, evidence of heat damage or burnt hoses, or rusted or damaged check valves and pipes. Repair components as necessary. After repairs, go to step 15). If all components are okay, see DIAGNOSTIC AIDS.
Repair short to voltage in AIR pump feed circuit between AIR pump and AIR pump relay. After repairs, go to step 15).
Repair short to ground in relay control circuit. After repairs, go to step 15).
Replace relay. After replacing relay, go to step 15).
Replace solenoid valve. After repairs, go to step 15).
Replace AIR cutoff valve/actuator assembly. After repairs, go to step 15).
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0410 is set, go to step 2). If DTC P0410 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

For any test that requires probing ECM or component harness connectors, use Connector Test Adapter Kit (J-35616-A). This will prevent damage to harness connector terminals.

Check AIR system for intermittent short to ground in relay control circuit, or short to battery voltage on pump feed circuit. Check for sticking relay contacts or a sticking AIR cutoff valve.

Using FREEZE FRAME data may aid in locating intermittent condition. If DTC cannot be duplicated, review information in FREEZE FRAME. Try to operate vehicle within same FREEZE FRAME conditions (RPM, MAF, vehicle speed and temperature). This may help to recreate malfunction.

DTC P0411 - AIR SYSTEM NO FLOW DETECTED

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions required to set DTC are

Short term fuel trim does not go above expected value within 6 seconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition on, with engine off. Using scan tool, command AIR pump relay on and off. If AIR pump turns on and off, go to step 10). If AIR pump does not turn on and off, go to next step.
Turn ignition off. Disconnect AIR pump relay connector. Turn ignition on, with engine off. Using test light connected to ground, probe relay battery supply circuit. If test light is on, go to next step. If test light is off, go to step 16).
Using test light connected to ground, probe relay switched battery feed circuit. If test light is on, go to next step. If test light is off, go to step 17).
Using test light connected to battery voltage, probe relay control circuit. Using scan tool, command AIR pump relay on and off. If test light turns on and off, go to next step. If test light does not turn on and off, go to step 9).
Using a fused jumper wire, jumper battery feed circuit to AIR pump feed circuit at relay connector. If AIR pump turns on, go to step 25). If AIR pump does not turn on, go to next step.
Leave fused jumper connected. Disconnect electrical connector from AIR pump. Using test light connected to ground, probe AIR pump harness connector feed circuit. If test light is on, go to next step. If test light is off, go to step 18).
Using test light connected to battery voltage, probe AIR pump harness connector ground circuit. If test light is on, go to step 27). If test light is off, go to step 19).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check harness continuity of control circuit. If continuity is present, go to step 29). If continuity is not present, go to step 20).
Start engine. Disconnect vacuum hose from cutoff valve. Using scan tool, command AIR solenoid valve on. If vacuum is present at cutoff valve, go to step 13). If vacuum is not present at cutoff valve, go to next step.
Disconnect manifold vacuum supply hose at AIR solenoid valve. If manifold vacuum is present at solenoid valve, go to next step. If manifold vacuum is not present at solenoid valve, go to step 21).
Reconnect vacuum supply hose, and disconnect hose to cutoff valve at solenoid valve. Connect the 2 hoses together using suitable coupler. If vacuum is present at cutoff valve, go to step 23). If vacuum is not present at cutoff valve, go to step 22).
Remove cutoff valve. Using a hand held vacuum pump, apply vacuum to valve and attempt to blow through valve. If valve is open, go to next step. If valve is not open, go to step 24).
Disconnect AIR pump outlet hose. Using scan tool, command AIR pump relay on and off. If air is present at AIR pump outlet when pump is running, go to next step. If air is not present at AIR pump outlet when pump is running, go to step 28).
Check for damaged or blocked AIR hoses and pipes between AIR pump and engine. Repair as necessary. After repairs, go to step 31).
Repair battery supply circuit to relay. After repairs, go to step 31).
Repair switched battery feed circuit to relay. After repairs, go to step 31).
Repair AIR pump feed circuit between AIR pump and AIR pump relay. After repairs, go to step 31).
Repair open or high resistance in AIR pump ground circuit. After repairs, go to step 31).
Repair open or high resistance in relay control circuit. After repairs, go to step 31).
Repair vacuum supply hose or plugged vacuum source. After repairs, go to step 31).
Repair vacuum hose to cutoff valve. After repairs, go to step 31).
Replace solenoid valve. After replacing valve, go to step 31).
Replace AIR cutoff valve. After replacing valve, go to step 31).
Check for poor connections and terminal tension at relay harness connector. Repair as necessary. After repairs, go to step 31). If connections and terminals are okay, go to next step.
Replace relay. After replacing relay, go to step 31).
Check for poor connections and terminal tension at AIR pump harness connector. Repair as necessary. After repairs, go to step 31). If connections and terminals are okay, go to next step.
Replace AIR pump. After replacing AIR pump, go to step 31).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 31). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0411 is set, repeat step 2). If DTC P0411 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

For any test that requires probing ECM or component harness connectors, use Connector Test Adapter Kit (J-35616-A). This will prevent damage to harness connector terminals.

DTC P0412 - AIR SOLENOID VALVE CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

AIR solenoid valve is supplied power via the main relay (switched battery feed circuit). ECM controls solenoid by grounding control circuit via an internal driver. Primary function of driver is to supply ground for component being controlled. Each driver has a fault line which is monitored by ECM. When ECM is commanding a component on, voltage of control circuit should be low (near zero volt). When ECM is commanding control circuit to component off, voltage should be high (near battery voltage). If fault detection circuit senses a voltage other than what is expected, this DTC will set.

Conditions required to set DTC are

A short to ground, open, or short to battery voltage detected on control circuit.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition on, with engine off. Using scan tool, command solenoid on and off. If solenoid turns on and off with each command, go to next step. If solenoid does not turn on and off with each command, go to step 5).
Turn ignition off. Disconnect ECM connector located in engine compartment, in relay center. Jumper main relay control circuit to ground. Using DVOM on 10-amp scale, measure current between ground and solenoid control circuit at ECM harness connector for 2 minutes. If current draw is 0.1-0.75 amp, see DIAGNOSTIC AIDS. If current draw is not 0.1-0.75 amp, go to next step.
Turn ignition off. Disconnect solenoid connector. Using DVOM, check resistance between ground and solenoid control circuit at ECM harness connector. If resistance is infinite, go to step 11). If resistance is not infinite, go to step 9).
Turn ignition off. Disconnect solenoid connector. Connect test light between solenoid coil terminals at solenoid harness connector. Turn ignition on. Using scan tool, command solenoid on and off. If test light turns on and off with each command, go to step 8). If test light does not turn on and off with each command, go to next step.
With test light connected to ground, probe solenoid harness connector switched battery feed circuit. If test light is on, go to next step. If test light is off, go to step 10).
Turn ignition off. Reconnect solenoid connector. Disconnect ECM connector located in engine compartment, in relay center. Jumper main relay control circuit to ground. Using a fused jumper wire connected to ground, probe solenoid control circuit at ECM harness connector. If solenoid operates, go to step 12). If solenoid does not operate, go to step 9).
Check connections at solenoid. Repair as necessary. After repairs, go to step 14). If connections are okay, go to step 11).
Repair solenoid control circuit. After repairs, go to step 14).
Repair switched battery feed circuit to solenoid. After repairs, go to step 14).
Replace solenoid. After replacing solenoid, go to step 14).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 14). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0412 is set, repeat step 2). If DTC P0412 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault.

DTC P0422/P0432 - TWC SYSTEM LOW EFFICIENCY BANK 1 & BANK 2

Note. For circuit reference, see WIRING DIAGRAMS article.

Three-Way Catalytic Converter (TWC) controls emissions of hydrocarbons (HC), carbon monoxide (CO) and oxides of nitrogen (NOx). Catalyst within converter promotes a chemical reaction which oxidizes HC and CO present in exhaust gas, converting them into water vapor and carbon monoxide. Catalyst reduces NOx, converting it to nitrogen. ECM monitors this process using HO2S located in exhaust stream after catalyst.

HO2S produces a signal indicating oxygen storage capacity of catalyst and indicates catalyst's ability to convert exhaust emissions effectively. If catalyst is functioning properly, HO2S signal will be less active then other HO2S located further upstream from catalyst. If ECM detects excessive post catalyst signal activity (outside of acceptable range) for an extended period of time, ECM will set this DTC. This indicates TWC converter's oxygen storage capacity is below a threshold considered acceptable.

Conditions required to set DTC are

Amplitude ratio (rear HO2S to front HO2S) must be greater than a predetermined value.
Condition must be met for about 5 minutes.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
If any other DTCs are set, go to applicable DTC. If no other DTCs are set, go to next step.
Verify catalytic converter is an original equipment part. Inspect catalytic converter for holes, dents or severe discoloration caused by excessive heat. Ensure internal catalytic converter rattle is not present. Inspect exhaust system for leaks, damage or loose or missing hardware. Ensure HO2S is secure and that pigtail and wiring are not damaged or contacting exhaust. Repair as necessary. After repairs, go to step 5). If components are okay, go to next step.
Replace catalytic converter, then go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0422 or DTC P0432 is set, go to step 2). If DTC P0422 or DTC P0432 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

DTC P0440 - EVAP SYSTEM

Note. For circuit reference, see WIRING DIAGRAMS article.

During specific operating conditions, ECM performs various tests on Evaporative Emission (EVAP) system. System tests consist of the following series of events.

After ensuring that EVAP purge solenoid valve duty cycle has dropped to zero percent, indicating that valve is closed, ECM commands EVAP canister vent valve closed, sealing system. ECM monitors accumulation of vapor pressure within fuel tank via fuel tank pressure sensor. EVAP test is aborted if vapor pressure is too high. If any vapor pressure is measured, it will be used later to compensate a pressure reading during small leak detection test. If a vacuum is measured which exceeds a calculated limit during vapor accumulation, this DTC will set. EVAP canister purge solenoid valve is then opened. Simultaneously, vent valve is opened.

If vapor pressure does not bleed off or bleeds off too slowly, this DTC is set. Once EVAP purge solenoid valve reaches its desired position for remainder of diagnostic test, vent valve will be closed again. This causes vacuum to be applied to entire EVAP system. ECM monitors vacuum level within system. If desired vacuum level cannot be achieved, or if vacuum level is reached but took too much time, DTC P0455 will set. Once desired vacuum level is reached, purge solenoid is closed, sealing system. ECM continues to monitor fuel tank pressure sensor signal, measuring rate of vacuum decay. If system holds vacuum, vent valve is opened and test is completed. In addition to system tests, ECM monitors circuit integrity of purge solenoid (DTC P0443), vent valve (DTC P0446) and fuel tank pressure sensor (DTC P0450).

Conditions required to set DTC are

Vent valve mechanical failure.
Purge solenoid mechanical failure.
Blocked or restricted lines, hoses or components.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
If DTCs P0443 or P0446 are also set, go to applicable DTC. If DTCs P0443 or P0446 are not set, go to next step.
Inspect EVAP system for disconnected, kinked or deteriorated hoses and lines. Check for loose hose connections or missing or loose fuel cap. Inspect for obvious damage to any system component. Repair components as necessary, then go to step 23). If components are okay, go to next step.
Disconnect manifold vacuum source hose at purge valve. Connect a vacuum gauge to manifold vacuum source hose. EVAP Pressure/Purge Diagnostic Station (J-41413) can be used for this purpose, if necessary. Start and operate engine to greater than 2000 RPM. Observe source vacuum level. If vacuum gauge indicates 15 in. Hg, go to next step. If vacuum gauge does not indicate 15 in. Hg, go to step 16).
Turn ignition off. Remove fuel cap. Turn ignition on, with engine off. Using scan tool, observe fuel tank pressure. If fuel tank pressure is minus one to plus one inch H2O, go to next step. If fuel tank pressure is not minus one to plus one inch H2O, go to DTC P0450.
Zero gauges on EVAP Pressure/Purge Diagnostic Station (J-41413) prior to installation. Connect pressure/purge diagnostic station to EVAP service port. Reinstall fuel cap. Plug EVAP vent hose or disconnect vent hose from vent valve and plug hose. Attempt to pressurize EVAP system using pressure/purge diagnostic station. Monitor pressure using gauge on EVAP pressure/purge diagnostic station. If pressure reading is 15 in. H2O, go to next step. If pressure reading is not 15 in. H2O, go to DTC P0455.
Maintain EVAP system pressure at 15 in. H2O. Observe fuel tank pressure on scan tool. If fuel tank pressure is at or greater than 11 in. H2O, go to next step. If fuel tank pressure is not at or greater than 11 in. H2O, go to DTC P0450.
Switch rotary switch on pressure/purge diagnostic station to HOLD and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 10). If pressure does not drop to less than 10 in. H2O within 2 minutes, go to next step.
Unplug EVAP vent hose and/or reconnect vent hose at vent valve. Disconnect ECM connector located in engine compartment, in relay center. Remove main relay. Using fused jumper, connect between battery circuit and switched battery feed circuit at relay harness connector. Using another fused jumper, ground EVAP vent valve control circuit at ECM harness connector. This closes vent valve. Restore system pressure to 15 in. H2O using EVAP pressure/purge diagnostic station. Switch rotary switch to HOLD and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 18). If pressure does not drop to less than 10 in. H2O within 2 minutes, see DIAGNOSTIC AIDS.
Disconnect fuel tank to EVAP canister vapor hose at canister and plug port on canister. Restore system pressure to 15 in. H2O using EVAP pressure/purge diagnostic station. Switch rotary switch to HOLD and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to next step. If pressure does not drop to less than 10 in. H2O within 2 minutes, go to step 14).
Disconnect purge valve to EVAP canister vapor hose at purge valve and plug hose. Restore system pressure to 15 in. H2O using EVAP pressure/purge diagnostic station. Switch rotary switch to HOLD and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to next step. If pressure does not drop to less than 10 in. H2O within 2 minutes, go to step 17).
Disconnect vent hose at EVAP canister and plug port on canister. Restore system pressure to 15 in. H2O using EVAP pressure/purge diagnostic station. Switch rotary switch to HOLD and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to next step. If pressure does not drop to less than 10 in. H2O within 2 minutes, go to step 20).
Disconnect and plug purge hose at EVAP canister. Restore system pressure to 15 in. H2O using EVAP pressure/purge diagnostic station. Switch rotary switch to HOLD position and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 21). If pressure does not drop to less than 10 in. H2O within 2 minutes, go to step 19).
Reconnect fuel tank vapor hose at EVAP canister. Disconnect fuel tank vapor hose at fuel tank and plug hose. Restore system pressure to 15 in. H2O using EVAP pressure/purge diagnostic station. Switch rotary switch to HOLD and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 22). If pressure does not drop to less than 10 in. H2O within 2 minutes, go to next step.
Reconnect fuel tank vapor hose at fuel tank. With EVAP pressure/purge diagnostic station connected to EVAP service port, continuously attempt to pressurize EVAP system by leaving control knob in PRESSURIZE position. Using Ultrasonic Leak Detector (J-41416), locate fuel tank system leaks. Check fuel tank, tank seams, fuel cap, fill pipe, sending unit, sending unit-to-tank seal, or fuel tank pressure sensor. Repair as necessary. After repairs, go to step 23).
Check for damaged vacuum source hose, blocked or restricted manifold vacuum port or low engine vacuum. Repair as necessary. After repairs, go to step 23).
Replace purge valve. After replacing valve, go to step 23).
Replace vent valve. After replacing valve, go to step 23).
Replace canister. After replacing canister, go to step 23).
Replace vent hose. After replacing hose, go to step 23).
Replace purge hose (valve-to-canister). After replacing hose, go to step 23).
Replace vapor hose (tank-to-canister). After replacing hose, go to step 23).
Ensure that vent valve is on (closed). Pressurize EVAP system to 15 in. H2O using EVAP pressure/purge diagnostic station. Monitor pressure using gauge on EVAP pressure/purge diagnostic station. Switch rotary switch to HOLD and observe pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 6). If pressure does not drop to less than 10 in. H2O within 2 minutes, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0440 is set, go to step 2). If DTC P0440 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for faulty fuel cap, damaged, pinched or blocked EVAP purge line, damaged EVAP vent hose, or pinched or blocked fuel tank vapor line. Check for EVAP canister purge valve or vent valve malfunction (non-electrical). Check for damaged EVAP canister. Inspect for leaking fuel sender assembly "O" ring, or leaking fuel tank or fuel filler neck.

DTC P0441 - EVAP SYSTEM INCORRECT PURGE FLOW

Note. For circuit reference, see WIRING DIAGRAMS article.

During specific operating conditions, ECM performs various tests on Evaporative Emission (EVAP) system. System tests consist of the following series of events.

Conditions required to set DTC are

Diagnostic test completed and determined that this DTC was detected.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition off. Disconnect vacuum source line from purge valve. Connect a hand-held vacuum pump to valve. Apply 15 in. Hg to purge valve. If purge valve holds vacuum, see DIAGNOSTIC AIDS. If purge valve does not hold vacuum, go to next step.
Replace purge valve. Inspect vacuum lines for traces of carbon. Carbon escaping from canister will cause new purge valve to fail. If this condition is present, replace canister. After replacing purge valve, go to next step.
Turn ignition off for 15 seconds. Using scan tool, select CLEAR INFO or CLEAR DTCs function to clear DTCs. Start engine and operate vehicle as close to conditions required for this DTC to set. Recheck for DTCs. If this DTC resets, repeat step 2). If this DTC does not reset, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for sticking purge valve, dirt or other contaminants, or incorrect vacuum hose routing.

DTC P0442 - EVAP SYSTEM (SMALL LEAK DETECTED)

Note. For circuit reference, see WIRING DIAGRAMS article.

During specific operating conditions, ECM performs various tests on Evaporative Emission (EVAP) system. System tests consist of the following series of events.

Conditions required to set DTC are

Diagnostic test completed and determined that this DTC was detected.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
If DTC P0441 or P0446 is also set, diagnose affected DTC first. If either DTCs are not set, go to next step.
Check for disconnected, kinked or deteriorated hoses/lines. Check loose hose connections, missing or loose fuel tank filler cap. Repair as necessary. After repairs, go to step 23). If no problems were found, go to next step.
Disconnect manifold vacuum source at purge valve. Install vacuum gauge to manifold vacuum source line. Start engine. Operate engine at greater than 2000 RPM and observe vacuum gauge. If vacuum gauge reads 15 in. Hg, go to next step. If vacuum gauge does not read 15 in. Hg, go to step 16).
Turn ignition off. Remove fuel filler cap. Turn ignition on, engine off. Using scan tool, observe fuel tank pressure reading. If scan tool reads -1 to 1 in. H2O, go to next step. If scan tool does not read -1 to 1 in. H2O, diagnose using DTC P0450 diagnostics.
Using EVAP Pressure/Purge Diagnostic Station (J 41413), connect diagnostic station to EVAP service port. Reinstall fuel filler cap. Disconnect ECM harness connector. Remove main relay. Using a fused jumper wire, connect jumper between battery voltage and ignition circuit in relay harness connector terminal. Using another fused jumper wire, ground EVAP vent valve control circuit in ECM harness connector (to close vent). Pressurize EVAP system using EVAP pressure/purge diagnostic station. Monitor pressure using gauge in diagnostic station. If 15 in. H2O can be achieved, go to next step. If 15 in. H2O cannot be achieved, diagnose using DTC P0455 diagnostics.
Maintain system pressure at 15 in. H2O. Observe fuel tank pressure on scan tool. If fuel tank pressure is at 15 in. H2O or greater than 11 in. H2O, go to next step. If fuel tank pressure is not 15 in. H2O or not greater than 11 in. H2O, diagnose using DTC P0450 diagnostics.
Switch rotary switch on diagnostic station to HOLD position and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to next step. If pressure does not drop to less than 10 in. H2O, no problem is found. See DIAGNOSTIC AIDS.
Disconnect and plug fuel tank vapor line at canister. Restore system pressure to 15 in. H2O. Set rotary switch on diagnostic station to HOLD position and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to next step. If pressure does not drop to less than 10 in. H2O within 2 minutes, go to step 14).
Disconnect and plug purge line at canister. Restore system pressure to 15 in. H2O. Set rotary switch on diagnostic station to HOLD position and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to next step. If pressure does not drop to less than 10 in. H2O within 2 minutes, go to step 17).
Disconnect and plug vent line at vent valve. Restore system pressure to 15 in. H2O. Set rotary switch on diagnostic station to HOLD position and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to next step. If pressure does not drop to less than 10 in. H2O within 2 minutes, go to step 18).
Disconnect and vent line at canister. Restore system pressure to 15 in. H2O. Set rotary switch on diagnostic station to HOLD position and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to next step. If pressure does not drop to less than 10 in. H2O within 2 minutes, go to step 20).
Disconnect and plug purge line at canister. Restore system pressure to 15 in. H2O. Set rotary switch on diagnostic station to HOLD position and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 21). If pressure does not drop to less than 10 in. H2O within 2 minutes, go to step 19).
Reconnect fuel tank vapor line at canister. Disconnect and plug fuel tank vapor line at fuel tank. Restore system pressure to 15 in. H2O. Set rotary switch on diagnostic station to HOLD position and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 22). If pressure does not drop to less than 10 in. H2O within 2 minutes, go to next step.
Reconnect fuel tank-to canister vapor line at fuel tank. Continuously attempt to pressurize EVAP system by leaving diagnostic station control knob in PRESSURIZE position. Using Ultrasonic Leak Detector (J 41416), check fuel tank for leaks at seams, filler pipe, sending unit and tank pressure sensor. Repair as necessary. After repairs or after checking for leaks, go to step 23).
Check for damaged vacuum source line, blocked or restricted vacuum port, or for low vacuum. Repair as necessary. After repairs, go to step 23).
Replace purge valve. Check for contamination causing purge valve to fail. After replacing valve, go to step 23).
Replace vent valve. After replacing valve, go to step 23).
Replace EVAP canister. After replacing canister, go to step 23).
Replace vent line. After replacing line, go to step 23).
Replace vent-to-canister purge line. After replacing purge line, go to step 23).
Replace vent-to-canister vapor line. After replacing vapor line, go to next step.
Pressurize EVAP system to 15 in. H2O using EVAP Pressure/Purge Diagnostic Station (J 41413). Monitor pressure using gauge on diagnostic station. Switch rotary switch on diagnostic station to HOLD position. Observe pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 6). If pressure does not drop to less than 10 in. H2O within 2 minutes, go to next step.
Using scan tool, select DTC, CLEAR INFO. Operate vehicle within the conditions for setting this DTC. Check for DTCs. If DTC P0442 is set, repeat step 5). If DTC P0442 is not set, go to next step.
If additional undiagnosed DTCs are set, go to applicable DTC test. If no additional DTCs are set, system is okay.

Check for missing or faulty fuel filler cap. Check for disconnected, damaged, pinched or blocked vapor lines or hoses. Check for damaged EVAP canister or purge valve. Check for leaking fuel sender assembly "O" ring or leaking fuel tank or fuel filler neck.

DTC P0443 - EVAP PURGE VALVE CONTROL

Note. For circuit reference, see WIRING DIAGRAMS article.

EVAP purge valve is supplied power via main relay (switched battery feed circuit). ECM controls valve by grounding control circuit via an internal driver. Primary function of driver is to supply ground for component being controlled. Each driver has a fault line which is monitored by ECM. When ECM is commanding a component on, voltage of control circuit should be low (near zero volt). When ECM is commanding control circuit to component off, voltage should be high (near battery voltage). If fault detection circuit senses a voltage other than what is expected, this DTC will set.

ECM will monitor EVAP purge valve circuit for short to ground, short to voltage, open circuit, open component or an internally shorted or excessively low resistance on EVAP purge valve circuit. When ECM detects any of these malfunctions, this DTC will set and affected driver will be disabled. ECM will continue to test circuit and if fault disappears, driver will be reactivated.

Conditions required to set DTC are

A short to ground, open, or short to battery voltage detected on control circuit.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition on, with engine off. Using scan tool, command purge valve on and off. If purge valve turns on and off with each command, go to next step. If purge valve does not turn on and off with each command, go to step 5).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Jumper main relay control circuit to ground. Using DVOM on 10-amp scale, measure current between ground and valve control circuit at ECM harness connector for 2 minutes. If current draw is 0.1-0.75 amp, see DIAGNOSTIC AIDS. If current draw is not 0.1-0.75 amp, go to next step.
Turn ignition off. Disconnect valve connector. Using DVOM, check resistance between ground and valve control circuit at ECM harness connector. If resistance is infinite, go to step 11). If resistance is not infinite, go to step 9).
Turn ignition off. Disconnect valve connector. Connect test light between valve harness connector terminals. Turn ignition on. Using scan tool, command valve on and off. If test light turns on and off with each command, go to step 8). If test light does not turn on and off with each command, go to next step.
With test light connected to ground, probe valve harness connector switched battery feed circuit. If test light is on, go to next step. If test light is off, go to step 10).
Turn ignition off. Reconnect valve connector. Disconnect ECM harness connector located in engine compartment relay center. Jumper main relay control circuit to ground. Using a fused jumper wire connected to ground, probe valve control circuit at ECM harness connector. If valve operates, go to step 12). If valve does not operate, go to step 9).
Check connections at valve. Repair as necessary. After repairs, go to step 14). If connections are okay, go to step 11).
Repair valve control circuit. After repairs, go to step 14).
Repair switched battery feed circuit to purge valve. After repairs, go to step 14).
Replace purge valve. After replacing valve, go to step 14).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 14). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0443 is set, go to step 2). If DTC P0443 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault.

DTC P0446 - EVAP VENT VALVE CONTROL

Note. For circuit reference, see WIRING DIAGRAMS article.

EVAP vent valve is supplied power via main relay (switched battery feed circuit). ECM controls valve by grounding control circuit via an internal driver. Primary function of driver is to supply ground for component being controlled. Each driver has a fault line which is monitored by ECM. When ECM is commanding a component on, voltage of control circuit should be low (near zero volt). When ECM is commanding control circuit to component off, voltage should be high (near battery voltage). If fault detection circuit senses a voltage other than what is expected, this DTC will set.

ECM will monitor EVAP vent valve circuit for short to ground, short to voltage, open circuit, open component or an internally shorted or excessively low resistance on EVAP valve circuit. When ECM detects any of these malfunctions, this DTC will set and affected driver will be disabled. ECM will continue to test circuit and if fault disappears, driver will be reactivated.

Conditions required to set DTC are

A short to ground, open, or short to battery voltage detected on control circuit.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition on, with engine off. Using scan tool, command vent valve on and off. If vent valve turns on and off with each command, go to next step. If vent valve does not turn on and off with each command, go to step 5).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Jumper main relay control circuit to ground. Using DVOM on 10-amp scale, measure current between ground and valve control circuit at ECM harness connector for 2 minutes. If current draw is 0.1-0.75 amp, see DIAGNOSTIC AIDS. If current draw is not 0.1-0.75 amp, go to next step.
Turn ignition off. Disconnect valve connector. Using DVOM, check resistance between ground and valve control circuit at ECM harness connector. If resistance is infinite, go to step 11). If resistance is not infinite, go to step 9).
Turn ignition off. Disconnect valve connector. Connect test light between valve harness connector terminals. Turn ignition on. Using scan tool, command valve on and off. If test light turns on and off with each command, go to step 8). If test light does not turn on and off with each command, go to next step.
With test light connected to ground, probe valve harness connector switched battery feed circuit. If test light is on, go to next step. If test light is off, go to step 10).
Turn ignition off. Reconnect valve connector. Disconnect ECM harness connector located in engine compartment relay center. Jumper main relay control circuit to ground. Using a fused jumper wire connected to ground, probe valve control circuit at ECM harness connector. If valve operates, go to step 12). If valve does not operate, go to step 9).
Check connections at valve. Repair as necessary. After repairs, go to step 14). If connections are okay, go to step 11).
Repair valve control circuit. After repairs, go to step 14).
Repair switched battery feed circuit to vent valve. After repairs, go to step 14).
Replace vent valve. After replacing valve, go to step 14).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 14). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0446 is set, go to step 2). If DTC P0446 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault.

DTC P0450 - EVAP FUEL TANK PRESSURE SENSOR CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

Fuel tank pressure sensor is mounted to sending unit at top of fuel tank. Sensor measures pressure changes within EVAP system. Sensor has a 5 volt reference, a ground and a signal circuit.

Sensor contains a diaphragm which changes resistance based on pressure. When EVAP system pressure is low (during purge), sensor output voltage is low. When EVAP system pressure is high, sensor output voltage is high. When ECM senses sensor signal voltage outside normal operating range of sensor, this DTC will set.

Conditions required to set DTC are

Tank pressure is more or less than 1.1 in. H2O for at least 5 seconds.
Tank pressure is greater than 0.4 H2O for at least 3 seconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition on, with engine off. Remove fuel cap. Using scan tool, monitor fuel tank pressure voltage. If voltage is 2.2-2.8 volts, go to next step. If voltage is not 2.2-2.8 volts, go to step 6).
Zero gauges on EVAP Pressure/Purge Diagnostic Station (J 41413) prior to installation. Connect diagnostic station to EVAP service port. Reinstall fuel cap. Disconnect vent hose at EVAP vent valve and plug hose. Using diagnostic station, pressurize EVAP system to 15 in. H2O. Monitor pressure using gauge on EVAP pressure/purge diagnostic station. Using scan tool, monitor fuel tank pressure sensor voltage. If sensor voltage is 3.3-3.9 volts, go to next step. If sensor voltage is not 3.3-3.9 volts, go to step 6).
Turn ignition on, with engine off. Wiggle fuel tank pressure sensor electrical connector, wiring harness and ECM harness connector while observing scan tool display. If voltage value displayed on scan tool changes when wiggling components, go to step 17). If voltage value displayed on scan tool does not change when wiggling components, go to next step.
Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Check for DTCs. If DTC P0450 is set, go to next step. If DTC P0450 is not set, see DIAGNOSTIC AIDS.
Disconnect fuel tank pressure sensor connector. Using DVOM, check voltage between ground and sensor harness connector signal circuit. If voltage is 4.7-5.3 volts, go to step 10). If voltage is not 4.7-5.3 volts, go to next step.
Turn ignition off. Leave sensor disconnected. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and sensor harness connector signal circuit. If any voltage is present, go to step 21). If no voltage is present, go to next step.
Using DVOM, check harness continuity of sensor signal circuit. If continuity is present, go to next step. If continuity is not present, go to step 22).
Using DVOM, check harness continuity between ground and sensor signal circuit. If continuity is present, go to step 23). If continuity is not present, go to step 27).
Using DVOM, check voltage between ground and sensor harness connector 5-volt reference circuit. If DVOM voltage is 4.7-5.3 volts, go to step 14). If voltage is not 4.7-5.3 volts, go to next step.
Turn ignition off. Leave sensor disconnected. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on. Using DVOM, check voltage between ground and sensor connector 5-volt reference circuit. If voltage is present, go to step 18). If no voltage is present, go to next step.
Using DVOM, check harness continuity of sensor 5-volt reference circuit. If continuity is present, go to next step. If continuity is not present, go to step 19).
Using DVOM, check harness continuity between ground and sensor 5 volt reference circuit. If continuity is present, go to step 20). If continuity is not present, go to step 27).
Turn ignition off. Using DVOM, check resistance between ground and sensor harness connector ground circuit. If resistance is 0-5 ohms, go to step 16). If resistance is not 0-5 ohms, go to next step.
Leave sensor disconnected. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check harness continuity of sensor ground circuit. If continuity is present, go to step 27). If continuity is not present, go to step 24).
Turn ignition on, with engine off. Using scan tool, monitor sensor voltage. Using a fused jumper wire, jumper sensor harness connector signal circuit to ground circuit. If scan tool display indicates zero volts, go to step 25). If scan tool does not indicate zero volts, go to step 28).
Repair harness and connections as necessary. After repairs, go to step 29).
Repair short to voltage in 5 volt reference circuit. After repairs, go to step 29).
Repair open or high resistance in 5 volt reference circuit. After repairs, go to step 29).
Repair short to ground in 5 volt reference circuit. After repairs, go to step 29).
Repair short to voltage in signal circuit. After repairs, go to step 29).
Repair open or high resistance in signal circuit. After repairs, go to step 29).
Repair short to ground in signal circuit. After repairs, go to step 29).
Repair open or high resistance in ground circuit. After repairs, go to step 29).
Check for poor connections and terminal tension at fuel tank pressure sensor harness connector. Repair as necessary. After repairs, go to step 29). If connections and terminals are okay, go to next step.
Replace fuel tank pressure sensor. After replacing tank pressure sensor, go to step 29).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 29). If connections and terminals are okay, go to next step.
Replace ECM. NEW ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0450 is set, go to step 2). If DTC P0450 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault. If sensor signal is only affected when harness is moved at component, and there is no problem with harness or connections, component may be faulty.

DTC P0455 - EVAP SYSTEM LARGE LEAK DETECTED

Note. For circuit reference, see WIRING DIAGRAMS article.

During specific operating conditions, ECM performs various tests on Evaporative Emission (EVAP) system. System tests consist of the following series of events.

Conditions required to set DTC are

Diagnostic test has run to completion and determined that this DTC was detected.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
If DTCs P0443 or P0446 are also set, go to applicable DTC. If DTCs P0443 or P0446 are not set, go to next step.
Inspect EVAP system for disconnected, kinked or deteriorated hoses and lines. Check for loose hose connections or missing or loose fuel cap. Inspect for obvious damage to any system component. Repair components as necessary. After repairs, go to step 23). If components are okay, go to next step.
Disconnect manifold vacuum source hose at purge valve. Connect a vacuum gauge to manifold vacuum source hose. EVAP Pressure/Purge Cartridge (J-41413) can be used for this purpose, if necessary. Operate engine at greater than 2000 RPM. Observe source vacuum level. If vacuum gauge indicates 15 in. Hg, go to next step. If vacuum gauge does not indicate 15 in. Hg, go to step 16).
Turn ignition off. Remove fuel cap. Turn ignition on, with engine off. Using scan tool, observe fuel tank pressure. If fuel tank pressure is -1 to 1 in. H2O, go to next step. If fuel tank pressure is not -1 to 1 in. H2O, go to DTC P0450.
Zero gauges on EVAP Pressure/Purge Cartridge (J-41413) prior to installation. Connect pressure/purge cartridge to EVAP service port. Reinstall fuel cap. Plug EVAP vent hose or disconnect vent hose from vent valve and plug hose. Attempt to pressurize EVAP system using pressure/purge cart. Monitor pressure using gauge on EVAP pressure/purge cartridge. If pressure reading is 15 in. H2O, go to next step. If pressure reading is not 15 in. H2O, go to step 10).
Maintain EVAP system pressure at 15 in. H2O. Observe fuel tank pressure on scan tool. If fuel tank pressure is at or greater than 11 in. H2O, go to next step. If fuel tank pressure is not at or greater than 11 in. H2O, go to DTC P0450.
Switch rotary switch on pressure/purge cart to HOLD and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 10). If pressure does not drop to less than 10 in. H2O within 2 minutes, go to next step.
Unplug EVAP vent hose and/or reconnect vent hose at vent valve. Disconnect ECM harness connector located in engine compartment relay center. Remove main relay. Using fused jumper, connect between battery circuit and switched battery feed circuit at relay harness connector. Using another fused jumper, ground EVAP vent valve control circuit at ECM harness connector. This closes vent valve. Restore system pressure to 15 in. H2O using pressure/purge cartridge. Switch rotary switch to HOLD position and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 18). If pressure does not drop to less than 10 in. H2O within 2 minutes, see DIAGNOSTIC AIDS.
Disconnect fuel tank to EVAP canister vapor hose at canister and plug port on canister. Restore system pressure to 15 in. H2O using pressure/purge cartridge. Switch rotary switch to HOLD position and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to next step. If pressure does not drop to less than 10 in. H2O within 2 minutes, go to step 14).
Disconnect purge valve to EVAP canister vapor hose at purge valve and plug hose. Restore system pressure to 15 in. H2O using pressure/purge cartridge. Switch rotary switch to HOLD position and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to next step. If pressure does not drop to less than 10 in. H2O within 2 minutes, go to step 17).
Disconnect vent hose at EVAP canister and plug port on canister. Restore system pressure to 15 in. H2O using pressure/purge cartridge. Switch rotary switch to HOLD position and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to next step. If pressure does not drop to less than 10 in. H2O within 2 minutes, go to step 20).
Disconnect purge hose at EVAP canister and plug hose. Restore system pressure to 15 in. H2O using pressure/purge cartridge. Switch rotary switch to HOLD position and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 21). If pressure does not drop to less than 10 in. H2O within 2 minutes, go to step 19).
Reconnect fuel tank vapor hose at EVAP canister. Disconnect fuel tank vapor hose at fuel tank and plug hose. Restore system pressure to 15 in. H2O using pressure/purge cartridge. Switch rotary switch to HOLD position and observe EVAP pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 22). If pressure does not drop to less than 10 in. H2O within 2 minutes, go to next step.
Reconnect fuel tank vapor hose at fuel tank. With pressure/purge cartridge connected to EVAP service port, continuously attempt to pressurize EVAP system by leaving cart control knob in PRESSURIZE position. Using Ultrasonic Leak Detector (J-41416), locate fuel tank system leaks. Check fuel tank, tank seams, fuel cap, fill pipe, sending unit, sending unit-to-tank seal, or fuel tank pressure sensor. Repair as necessary. After repairs, go to step 23).
Check for damaged vacuum source hose, blocked or restricted manifold vacuum port or low engine vacuum. Repair as necessary. After repairs, go to step 23).
Replace purge valve. After replacing valve, go to step 23).
Replace vent valve. After replacing valve, go to step 23).
Replace canister. After replacing canister, go to step 23).
Replace vent hose. After replacing hose, go to step 23).
Replace purge hose (valve-to-canister). After replacing hose, go to step 23).
Replace vapor hose (tank-to-canister). After replacing hose, go to step 23).
Ensure that vent valve is on (closed). Pressurize EVAP system to 15 in. H2O using pressure/purge cartridge. Monitor pressure using gauge on EVAP pressure/purge cartridge. Switch rotary switch on cart to HOLD position and observe pressure gauge. If pressure drops to less than 10 in. H2O within 2 minutes, go to step 6). If pressure does not drop to less than 10 in. H2O within 2 minutes, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0455 is set, repeat step 2). If DTC P0455 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

If no apparent cause of large leak can be found, vehicle may have been left running during refueling. By coincidence, proper conditions may have been met to set DTC during time fuel cap was off or loose.

DTC P0501 - VEHICLE SPEED SIGNAL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

A processed wheel speed sensor signal is sent from ABS controller to theft deterrent module. Signal is then sent from theft deterrent module to ECM. ECM calculates vehicle speed from this signal. Vehicle speed circuit is increased to battery voltage within ECM. This DTC covers vehicle speed signal circuit from theft deterrent module to ECM. Circuit from ABS controller to theft deterrent module is covered by ABS controller diagnosis.

Conditions required to set DTC are

Vehicle speed signal is less than 3 MPH for longer than 5 seconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step. NOTE: Support lower control arms to ensure drive axles are in normal horizontal position or drive axles will be damaged.
Turn ignition off. Raise and support drive axles. Start engine. Turn traction control system off, if equipped. With engine idling, place transmission in gear. Using scan tool, monitor vehicle speed. If displayed vehicle speed is greater than zero MPH, see DIAGNOSTIC AIDS. If displayed vehicle speed is zero MPH, go to next step.
Turn ignition off. Disconnect ECM harness connector. Connect test light between battery voltage and vehicle speed signal circuit at ECM harness connector. Turn ignition on, with engine off. Using DVOM set to AC, Hz, 4-volt scale, check voltage between ground and vehicle speed signal circuit at ECM harness connector. If DVOM indicates frequency 100-900 Hz, go to step 5). If DVOM does not indicate frequency 100-900 Hz, go to next step.
Turn ignition off. Disconnect theft deterrent module connector. Check vehicle speed signal circuit for open, short to ground or short to voltage. Repair as necessary. After repairs, go to step 6). If circuit is okay, go to step 7).
Turn ignition off. Reconnect ECM connector. Disconnect theft deterrent module connector. Connect Signal Generator Tester (J-33431-B) between ground and vehicle speed signal circuit at theft deterrent module harness connector. Turn ignition on. Turn tester on. Set tester to generate a VSS signal. Using scan tool, monitor vehicle speed. If displayed vehicle speed is greater than zero MPH, diagnose anti-lock brake system. If displayed vehicle speed is zero MPH, go to step 8).
Repair vehicle speed signal circuit between theft deterrent module harness connector and ECM. After repairs, go to step 10).
Check for poor connections and terminal tension at theft deterrent module harness connector. Repair as necessary. After repairs, go to step 10). If connections and terminals are okay, diagnose theft deterrent system.
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 10). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0501 is set, go to step 2). If DTC P0501 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault. If sensor signal is only affected when harness is moved at component, and there is no problem with harness or connections, component may be faulty.

DTC P0505 - IAC VALVE CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

IAC system controls idle speed by allowing a controlled amount of air to by-pass throttle plate via passage in IAC valve. IAC valve consists of a rotating shutter that is held in a neutral position by opposing springs within IAC valve assembly.

Switched battery feed circuit is provided to drive unit within IAC valve. ECM controls valve via 2 control circuits (one to open valve and the other to close valve). ECM pulse width modulates both control circuits simultaneously. Ratio of frequency between 2 signals determines direction and amount that drive unit rotates shutter within valve. As shutter closes, by-pass airflow is reduced and idle speed decreases.

To increase idle speed, ECM commands shutter open, allowing more air to by-pass throttle plates. ECM will monitor IAC valve control circuit for short to ground, short to voltage, open circuit, or an internally shorted or excessively low resistance in IAC valve control circuit. When ECM detects any of these conditions, this DTC will set and affected driver will be disabled. ECM will continue to test circuit and if fault disappears, driver will be reactivated.

Conditions required to set DTC are

ECM senses a short to ground, open, or short to voltage on either IAC valve control circuit.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition off for 15 seconds. Start engine. Using scan tool, command DESIRED IDLE SPEED up to 1500 RPM then down to 500 RPM. Repeat commanded RPM. If engine speed is controllable using scan tool, fault is not present. See DIAGNOSTIC AIDS. If engine speed is not controllable using scan tool, go to next step.
Turn ignition off. Disconnect IAC valve connector. Turn ignition on, with engine off. Using test light connected to ground, probe switched battery feed circuit at IAC valve harness connector. If test light is on, go to next step. If test light is off, go to step 9).
Using DVOM connected to ground and set to DC volts/percent, measure duty cycle on both control circuits. If duty cycle is greater than 5 percent on both circuits, go to step 14). If duty cycle is less than 5 percent on both circuits, go to next step.
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on, with engine off. Using test light connected to ground, probe affected control circuit at IAC valve harness connector. If test light is on, go to step 10). If test light is off, go to next step.
Turn ignition off. Using DVOM, check harness continuity of affected control circuit between ECM and IAC valve harness connectors. If continuity is present, go to next step. If no continuity exists, go to step 11).
Using DVOM, check harness continuity between ground and affected control circuit. If continuity is present, go to step 12). If continuity is not present, go to next step.
Using DVOM, check harness continuity between 2 control circuits. If continuity is present, go to step 13). If continuity is not present, go to step 16).
Repair switched battery feed circuit. After repairs, go to step 18).
Repair short to voltage in control circuit. After repairs, go to step 18).
Repair open or high resistance in control circuit. After repairs, go to step 18).
Repair short to ground in control circuit. After repairs, go to step 18).
Repair control circuits shorted together. After repairs, go to step 18).
Check for poor connections and terminal tension at IAC valve harness connector. Repair as necessary. After repairs, go to step 18). If connections and terminals are okay, go to next step.
Replace IAC valve. After replacing valve, go to step 18).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary, then go to step 18). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0505 is set, go to step 2). If DTC P0505 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault.

DTC P0506 - IDLE SPEED LOW (IAC RESPONDING)

Note. For circuit reference, see WIRING DIAGRAMS article.

IAC system controls idle speed by allowing a controlled amount of air to by-pass throttle blade via a passage in IAC valve. ECM controls IAC system to maintain a desired idle speed. Speed may vary depending on input to ECM and other criteria. If ECM detects engine speed is outside IAC system's range of control at idle, this DTC will set.

Conditions required to set DTC are

Actual engine RPM is less than desired idle speed by at least 100 RPM.
Short term air trim is greater than 5.6 gm/s.
Conditions are met for greater than 10 seconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start engine. Load engine by turning on several accessories (A/C, headlights, rear defogger, etc.). If actual engine speed is not greater than 200 RPM or less than 100 RPM of desired idle speed, fault is not present. See DIAGNOSTIC AIDS. If actual engine speed is greater than 200 RPM or less than 100 RPM of desired idle speed, go to next step.
If engine RPM is too high, go to next step. If engine RPM is not too high, go to step 5).
Check for vacuum leaks, throttle blade not closing properly, faulty PCV system or mechanical IAC valve failure. Repair component as necessary. After repairs, go to step 6).
Check for excessive deposits in throttle body or IAC valve passages. Check for kinked or obstructed IAC air supply hose. Inspect for IAC valve mechanical failure. Check for parasitic load on engine (transmission problem, belt driven accessory problem, etc.). Check for mechanical engine problem. Repair as necessary. After repairs, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Operate vehicle within conditions for this DTC to set. Check for DTCs. If DTC P0506 is set, go to step 2). If DTC P0506 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault.

DTC P0507 - IDLE SPEED HIGH (IAC RESPONDING)

Note. For circuit reference, see WIRING DIAGRAMS article.

Conditions required to set DTC are

Actual engine RPM is greater than desired idle speed by at least 200 RPM.
Short term air trim is lower than -1.66 gm/s.
Fuel cutoff occurs greater than 3 times when diagnostic is performed.
Conditions are met for greater than 8 seconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Start engine. Load engine by turning on several accessories (A/C, headlights, rear defogger, etc.). If actual engine speed is not greater than 200 RPM or less than 100 RPM of desired idle speed, fault is not present. See DIAGNOSTIC AIDS. If actual engine speed is greater than 200 RPM or not less than 100 RPM of desired idle speed, go to next step.
If engine RPM is too high, go to next step. If engine RPM is not too high, go to step 5).
Check for vacuum leaks, throttle blade not closing properly, faulty PCV system or mechanical IAC valve failure. Repair component as necessary. After repairs, go to step 6).
Check for excessive deposits in throttle body or IAC valve passages. Check for kinked or obstructed IAC air supply hose. Inspect for IAC valve mechanical failure. Check for parasitic load on engine (transmission problem, belt driven accessory problem, etc.). Check for mechanical engine problem. Repair as necessary. After repairs, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0507 is set, go to step 2). If DTC P0507 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault.

DTC P0560 - SYSTEM VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article.

ECM continuously monitors system voltage. Since voltages that are less than 9 volts or greater than 16 volts could cause improper system operation and/or component damage, ECM operates in a default mode if an ECM voltage DTC is set. If system voltage is low, ECM will raise idle speed to increase alternator output. If system voltage is high, ECM disables most outputs to protect components.

Serial data is disrupted when system voltage is below 9 volts or above 16 volts. A scan tool may not display data if system voltage is outside this range. Because of this, a DVOM must be used to monitor system voltage when checking to see if fault is currently present.

Conditions required to set DTC are

ECM senses system voltage less than 9 volts for at least 2 seconds.
ECM senses system voltage less than 2.54 volts for at least 1 second.
ECM senses system voltage greater than 16 volts for at least 1 second.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Using scan tool, check system voltage. If scan tool indicates voltage greater than 16 volts, go to next step. If scan tool indicates voltage less than 16 volts, go to step 4).
Start engine. Turn all accessories off. Raise engine RPM to at least 2500 RPM. Using DVOM, measure voltage at battery. If battery voltage is greater than 16 volts, repair starting or charging system. If battery voltage is less than 16 volts, go to step 7).
Allow engine to idle. Load electrical system by turning on headlights and high blower. Using DVOM, measure voltage at battery. If battery voltage is less than 9 volts, repair starting or charging system. If battery voltage is greater than 9 volts, go to next step.
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Turn ignition on, with engine off. Using DVOM, check voltage at ECM harness connector battery feed circuit. If voltage is less than 9 volts, go to step 9). If voltage is greater than 9 volts, go to next step.
Check for faulty connections at ECM. Repair as necessary. After repairs, go to step 10). If connections are okay, go to next step.
Reconnect ECM connector (if previously disconnected). Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0560 is set, go to next step. If DTC P0560 is not set, see DIAGNOSTIC AIDS.
Replace ECM. NEW ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Repair high resistance in battery feed circuit to ECM. After repairs, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0560 is set, go to step 2). If DTC P0560 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Extremely low voltage (less than 7.5 volts) may cause loss of serial data and MIL may not function. Low system voltage may cause other DTCs to set.

ECM contains data which is essential to engine operation. ECM continuously checks integrity of this data.

Conditions required to set DTC are

ECM determines that an internal data test did not pass.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0601 is set, go to step 2). If DTC P0601 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Replace ECM even if this DTC exists only in history.

This DTC indicates that ECM's internal EEPROM has not been flashed with any vehicle software, or an error occurred during programming.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Flash ECM with correct software. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. If DTC resets, go to next step. If DTC does not reset, go to step 5).
Verify that equipment being used is functioning properly and that all cable connections are clean and tight. Attempt to flash ECM again. If DTC P0602 resets, go to next step. If DTC P0602 does not reset, go to step 5).
Replace ECM, then go to step 2).
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0602 is set, go to step 2). If DTC P0602 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

ECM contains data which is essential to engine operation. ECM continuously checks integrity of this data.

Conditions required to set DTC are

ECM determines that an internal data test did not pass.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing PCM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0604 is set, go to step 2). If DTC P0604 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Replace ECM even if this DTC exists only in history.

DTC P1112 - INTAKE PLENUM SWITCHOVER VALVE CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

Multi-Ram system uses variable air induction tuning to achieve maximum performance and efficiency over entire operating range of engine. System consists of 2 main components. Intake manifold contains intake plenum switchover valve. This vacuum operated valve is essentially a moveable divider that changes airflow characteristics of intake manifold. Vacuum to valve is controlled by an ECM controlled solenoid valve.

Intake resonance switchover valve is located in air intake duct assembly in front of engine. This vacuum operated valve is also a moveable divider that changes tuning of air intake system. Vacuum to valve is controlled by ECM controlled solenoid valve. By opening and closing these valves independently in different combinations, 4 different air flow configurations can be created, each optimized to a particular set of engine operating conditions.

Both solenoid valves are supplied power via main relay (switched battery feed circuit). Both solenoid valves have a control circuit to ECM. ECM controls a valve by grounding control circuit via an internal driver. Primary function of driver is to supply ground for component being controlled. Each driver has a fault line which is monitored by ECM. When ECM is commanding a component on, control circuit voltage should be low (near zero volts). When ECM is commanding control circuit to a component off, circuit voltage should be high (near battery voltage). If fault detection circuit senses a voltage other than what is expected, this DTC will set.

ECM will monitor circuit for short to ground, short to voltage, open or an internally shorted or excessively low resistance in circuit. When ECM detects any of these malfunctions, this DTC will set and affected driver will be disabled. ECM will continue to test circuit and if fault disappears, driver will be reactivated.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition on, with engine off. Using scan tool, command valve on and off. If valve turns on and off with each command, go to next step. If valve does not turn on and off with each command, go to step 5).
Turn ignition off. Disconnect ECM connector located in engine compartment, in relay center. Jumper main relay control circuit to ground. Using DVOM on 10-amp scale, measure current between ground and valve control circuit at ECM harness connector for 2 minutes. If current draw is 0.1-0.75 amp, see DIAGNOSTIC AIDS. If current draw is not 0.1-0.75 amp, go to next step.
Turn ignition off. Disconnect valve connector. Using DVOM, measure resistance between ground and valve control circuit at ECM harness connector. If resistance is infinite, go to step 11). If resistance is not infinite, go to step 9).
Turn ignition off. Disconnect valve connector. Connect test light between valve harness connector terminals. Turn ignition on. Using scan tool, command valve on and off. If test light turns on and off with each command, go to step 8). If test light does not turn on and off with each command, go to next step.
With test light connected to ground, probe switched battery feed circuit at valve harness connector. If test light is on, go to next step. If test light is off, go to step 10).
Turn ignition off. Reconnect valve connector. Disconnect ECM harness connector located in engine compartment relay center. Jumper main relay control circuit to ground. Using a fused jumper wire connected to ground, probe valve control circuit at ECM harness connector. If solenoid operates, go to step 12). If solenoid does not operate, go to step 9).
Check connections at valve. Repair as necessary. After repairs, go to step 14). If connections are okay, go to step 11).
Repair valve control circuit. After repairs, go to step 14).
Repair switched battery feed circuit to valve. After repairs, go to step 14).
Replace valve. After replacing valve, go to step 14).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 14). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P1112 is set, go to step 2). If DTC P1112 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault.

DTC P1113 - INTAKE RESONANCE SWITCHOVER VALVE CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition on, with engine off. Using scan tool, command valve on and off. If valve turns on and off with each command, go to next step. If valve does not turn on and off with each command, go to step 5).
Turn ignition off. Disconnect ECM connector located in engine compartment, in relay center. Jumper main relay control circuit to ground. Using DVOM on 10-amp scale, measure current between ground and valve control circuit at ECM harness connector for 2 minutes. If current draw is 0.1-0.75 amp, see DIAGNOSTIC AIDS. If current draw is not 0.1-0.75 amp, go to next step.
Turn ignition off. Disconnect valve connector. Using DVOM, measure resistance between ground and valve control circuit at ECM harness connector. If resistance is infinite, go to step 11). If resistance is not infinite, go to step 9).
Turn ignition off. Disconnect valve connector. Connect test light between valve harness connector terminals. Turn ignition on. Using scan tool, command valve on and off. If test light turns on and off with each command, go to step 8). If test light does not turn on and off with each command, go to next step.
With test light connected to ground, probe switched battery feed circuit at valve harness connector. If test light is on, go to next step. If test light is off, go to step 10).
Turn ignition off. Reconnect valve connector. Disconnect ECM connector located in engine compartment, in relay center. Jumper main relay control circuit to ground. Using a fused jumper wire connected to ground, probe valve control circuit at ECM harness connector. If solenoid operates, go to step 12). If solenoid does not operate, go to step 9).
Check connections at valve. Repair as necessary. After repairs, go to step 14). If connections are okay, go to step 11).
Repair valve control circuit. After repairs, go to step 14).
Repair switched battery feed circuit to switchover valve. After repairs are complete, go to step 14).
Replace valve. After replacing valve, go to step 14).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 14). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P1113 is set, go to step 2). If DTC P1113 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Check for switched harness. Ensure IAT sensor electrical connector and intake resonance switchover valve electrical connectors are not switched. This can cause IAT sensor reading to remain constant. Allow vehicle to idle a few minutes. Using scan tool, observe IAT sensor.

Check for damaged wiring harness. If harness appears to be okay, observe scan tool while moving related connectors and wiring harnesses. A change in scan tool display may help to locate fault.

If this DTC sets, and no misfire is currently present, vehicle may simply have been run low on fuel. This DTC being present with a properly functioning fuel sender circuit eliminates need for lengthy misfire diagnosis. Verify that there is an adequate fuel supply in tank.

Conditions required to set DTC are

Fuel level signal greater than 6.82 volts.

Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . If OBD system check was performed previously, go to DTC P0300 .

When ignition switch is turned to on position, and ECM lights MIL (bulb check), voltage change on MIL control circuit is used as a wake up signal to theft deterrent module. If a problem with this circuit prevents theft deterrent module from receiving wake up signal, this DTC will set.

Head of ignition key contains a transponder which is matched to a code in theft deterrent system. If a key is used that has the wrong or no code, vehicle will not start, and this DTC will set. DTC can also indicate theft deterrent module has detected a problem within theft deterrent system. Theft deterrent module sends a signal to ECM, causing this DTC to set.

Conditions required to set DTC are

Requested by theft deterrent module.

Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . If OBD system check was performed previously, perform theft deterrent system diagnosis.

DTC P1502 - THEFT DETERRENT SYSTEM NO PASSWORD RECEIVED

Note. For circuit reference, see WIRING DIAGRAMS article.

This DTC will set if ECM has not been programmed with frequency code of theft deterrent module, or if there is a problem with circuit used for transmitting data (vehicle speed signal circuit).

Conditions required to set DTC are

ECM has not received frequency code from theft deterrent module.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step. NOTE: Support lower control arms to ensure drive axles are in normal horizontal position or drive axles will be damaged.
Turn ignition off. Raise and support drive axles. Start engine. Turn traction control system off, if equipped. With engine idling, place transmission in gear. Using scan tool, monitor vehicle speed. If displayed vehicle speed is greater than zero MPH, see DIAGNOSTIC AIDS. If displayed vehicle speed is zero MPH, go to next step.
Turn ignition off. Disconnect ECM connector located in engine compartment, in relay center. Connect test light between battery voltage and vehicle speed signal circuit at ECM harness connector. Turn ignition on, with engine off. Using DVOM set to AC, Hz, 4 volt scale, check voltage between ground and vehicle speed signal circuit at ECM harness connector. If DVOM indicates frequency 100-900 Hz, go to step 5). If DVOM does not indicate frequency 100-900 Hz, go to next step.
Turn ignition off. Disconnect theft deterrent module harness connector. Check vehicle speed signal circuit for open, short to ground or short to voltage. Repair as necessary, then go to step 6). If circuit is okay, go to step 7).
Turn ignition off. Reconnect ECM connector. Disconnect theft deterrent module connector. Connect Signal Generator Tester (J-33431-B) between ground and vehicle speed signal circuit at theft deterrent module harness connector. Turn ignition on. Turn tester on. Set tester to generate a VSS signal. Using scan tool, monitor vehicle speed. If displayed vehicle speed is greater than zero MPH, diagnose anti-lock brake system. If displayed vehicle speed is zero MPH, go to step 8).
Repair vehicle speed signal circuit between theft deterrent module harness connector and ECM. After repairs, go to step 10).
Check for poor connections and terminal tension at theft deterrent module harness connector. Repair as necessary. After repairs, go to step 10). If connections and terminals are okay, diagnose theft deterrent system.
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 10). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P1502 is set, go to step 2). If DTC P1502 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

If ECM and theft deterrent module have not been properly programmed, this DTC may set and vehicle will not start.

This DTC indicates that ECM has been programmed with a frequency code that does not match code in theft deterrent module.

Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . If OBD system check was performed previously, see DIAGNOSTIC AIDS.

Wrong ignition key, or use of a key without transponder will cause this DTC to set as well as no-start condition. If ECM and theft deterrent module have not been properly programmed, this DTC may set and vehicle will not start.

A complete loss of battery voltage at ECM will cause a no-start condition with no MIL. However, an intermittent loss of battery voltage can also set this DTC. If ECM has been disconnected, or battery power was interrupted during service procedure, this DTC will set.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
If engine starts and runs, fault is not present. See DIAGNOSTIC AIDS. If engine does not start and run, see BASIC TESTING article.

Extremely high temperatures can affect ECM, thus reducing reliability. ECM is enclosed within relay center in engine compartment. A small fan, located in left front fender, directs fresh air through relay center to reduce ECM temperature. This fan is not ECM controlled and is designed to operate in conjunction with engine cooling fans. An inoperative fan, or an obstructed airflow may allow ECM to overheat. If ECM detects it is getting too hot, this DTC will set.

Conditions required to set DTC are

ECM temperature is greater than 221°F (105°C), or internal temperature sensor value is less than -58°F (-50°C) or greater than 284°F (140°C).

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Allow ECM to cool down. Start engine and operate vehicle. Check for DTCs. If DTC P01601 is set, go to step 4). If DTC P01601 is not set, go to next step.
Ensure ECM and/or other components are properly mounted in engine compartment relay center. Ensure relay center cover is installed properly and that relay center is not damaged. Check for debris and other obstructions in airflow path. Check for debris in fan and fan air inlet. Repair as necessary. If no problem is found, and fans do not operate, see SYSTEM/COMPONENT TESTS article to diagnosis electric cooling fans.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle.

ECM employs an internal circuit to continuously monitor knock control evaluation circuit. Knock Sensor (KS) module circuit contains circuitry that allows ECM to utilize KS signals and diagnose KS sensors and circuitry. KS module is not a replaceable component. If ECM detects a fault in ability of circuit to sample these signals, this DTC will set.

Conditions required to set DTC are

ECM detects a fault in internal knock sensor control circuit.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P1602 is set, go to step 2). If DTC P1602 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

This DTC indicates that a transmission related OBD-II failure has occurred. Transmission Control Module (TCM) controls a dedicated service transmission light, which is illuminated when a failure is reported by certain non-emission related TCM diagnostics. TCM has no direct control of engine MIL, but if transmission fault occurs that is emission related, MIL must illuminate. A MIL request circuit between ECM and TCM provides a means for illuminating MIL, even though fault was detected by TCM. This circuit is increased to battery voltage within ECM. To illuminate MIL, TCM lowers circuit voltage. ECM detects this and DTC is set, which illuminates MIL.

Conditions required to set DTC are

An OBD-II transmission DTC has been stored by TCM.

Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . If OBD system check was performed previously, diagnose transmission malfunction. See the AUTO TRANS DIAGNOSIS article in the AUTO TRANS DIAGNOSIS section.

Conditions required to set DTC are

A short to ground, open or short to voltage detected on MIL request circuit.
Condition is present for at least 2.5 seconds.

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition off. Disconnect TCM connector. Turn ignition on, with engine off. Using DVOM, measure voltage between ground and MIL request circuit at TCM harness connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step 4).
Using test light connected to ground, probe TCM harness connector MIL request circuit. If test light is on, go to step 7). If test light is off, go to step 6).
Turn ignition off. Disconnect ECM connector located in engine compartment, in relay center. Using DVOM, check harness continuity of MIL request circuit. If continuity is present, go to next step. If continuity is not present, go to step 8).
Using DVOM, check harness continuity between ground and MIL request circuit. If continuity is present, go to step 9). If continuity is not present, go to step 11).
Turn ignition off. Reconnect TCM connector. Disconnect ECM connector located in engine compartment, in relay center. Using test light connected to battery voltage, probe TCM harness connector MIL request circuit. If test light is on, go to step 10). If test light is off, fault is not present. See DIAGNOSTIC AIDS.
Repair short to voltage in request circuit. After repairs, go to step 13).
Repair open or high resistance in request circuit. After repairs, go to step 13).
Repair short to ground in request circuit. After repairs, go to step 13).
Replace TCM. After replacing TCM, go to step 13).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 13). If connections and terminals are okay, go to next step.
Replace ECM. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P1701 is set, go to step 2). If DTC P1701 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

DTC P1740 - TORQUE CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article.

On traction control, ECM pulls this circuit up to 12 volts and monitors this circuit. The TCM also monitors this circuit. Circuit provides unidirectional communication between ECM and TCM. Messages are sent every 25 milliseconds. This data is used to reduce engine torque during transmission shift events in order to improve shift feel. If ECM detects a problem on this circuit, DTC will set.

On traction control, ECM pulls this circuit down to zero volts and monitors this circuit. The ABS/TC module also monitors this circuit. Circuit provides unidirectional communication between the 2 controllers. This data is used to reduce engine torque during a wheel spin/slipping condition where traction control is needed. If ECM detects a problem on this circuit, DTC will set.

Conditions required to set DTC are

For transmission control
Circuit is tested continuously.
Signal remains low for at least 2 seconds.
Signal is low 3 times for at least 2.5 seconds.
Above conditions met within 10 seconds.
For traction control
Engine speed greater than 600 RPM.
Circuit is tested continuously.
Signal is out of range.
Conditions met for 2.5 seconds.

Diagnostic Procedures (Transmission Control)

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition off. Disconnect Transmission Control Module (TCM) harness connector. Turn ignition on, with engine off. Using DVOM, check voltage between ground and torque management request circuit at TCM harness connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step 4).
Using test light connected to ground, probe torque management request circuit at TCM harness connector. If test light illuminates, go to step 7). If test light does not illuminate, go to step 6).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check harness continuity of torque management request circuit. If continuity is present, go to next step. If continuity is not present, go to step 8).
Using DVOM, check harness continuity between ground and torque management request circuit. If continuity is present, go to step 9). If continuity is not present, go to step 11).
Turn ignition off. Reconnect TCM harness connector. Disconnect ECM harness connector located in engine compartment relay center. Using test light connected to battery voltage, probe torque management request circuit at TCM harness connector. If test light illuminates, go to step 10). If test light does not illuminate, fault is not present. See DIAGNOSTIC AIDS.
Repair short to voltage in request circuit. After repairs, go to step 13).
Repair open or high resistance in request circuit. After repairs, go to step 13).
Repair short to ground in request circuit. After repairs, go to step 13).
Replace TCM. After replacing TCM, go to step 13).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 13). If connections and terminals are okay, go to next step.
Replace ECM. NEW ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P1740 is set, go to step 2). If DTC P1740 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Diagnostic Procedures (Traction Control)

Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
Turn ignition off. Disconnect ABS/TC module connector. Turn ignition on, with engine off. Using DVOM, check voltage between ground and torque management request circuit at ABS/TC module harness connector. If zero volts is present, go to next step. If zero volts is not present, go to step 4).
Using test light connected to ground, probe torque management request circuit at ABS/TC module harness connector. If test light illuminates, go to step 7). If test light does not illuminate, go to step 6).
Turn ignition off. Disconnect ECM harness connector located in engine compartment relay center. Using DVOM, check harness continuity of torque management request circuit. If continuity is present, go to next step. If continuity is not present, go to step 8).
Using DVOM, check harness continuity between ground and torque management request circuit. If continuity is present, go to step 9). If continuity is not present, go to step 11).
Turn ignition off. Reconnect ABS/TC module connector. Disconnect ECM harness connector located in engine compartment relay center. Using test light connected to battery voltage, probe torque management request circuit at ABS/TC module harness connector. If test light illuminates, go to step 10). If test light does not illuminate, fault is not present. See DIAGNOSTIC AIDS.
Repair short to voltage in request circuit. After repairs, go to step 13).
Repair open or high resistance in request circuit. After repairs, go to step 13).
Repair short to ground in request circuit. After repairs, go to step 13).
Replace TCM. After replacing TCM, go to step 13).
Check for poor connections and terminal tension at ECM harness connector. Repair as necessary. After repairs, go to step 13). If connections and terminals are okay, go to next step.
Replace ECM. NEW ECM must be programmed with theft deterrent module frequency code currently on vehicle. After replacing ECM, go to next step.
Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P1740 is set, go to step 2). If DTC P1740 is not set, go to next step.
If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.

Use Connector Test Adapter (J 35616-A) for any test that requires probing ECM/TCM harness connector to prevent damage to harness connector terminals. Check for poor connections at ECM, TCM or related components. Check harness connectors and terminals for proper connections.

See also:
• DIAGNOSTIC PROCEDURE
• POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK
• HARD OR INTERMITTENT TROUBLE CODE DETERMINATION
• P0100
• P0101
• P0110
• P0115
• P0116
• P0120
• P0130
• P0131
• P0132
• P0133
• P0134
• P0135
• P0136
• P0137
• P0138
• P0140
• P0141
• P0150
• P0151
• P0152
• P0153
• P0155
• P0156
• P0157
• P0158
• P0160
• P0161
• P0171
• P0172
• P0174
• P0175
• P0201
• P0202
• P0203
• P0204
• P0205
• P0206
• P0230
• P0300
• P0301
• P0302
• P0303
• P0304
• P0305
• P0306
• P0325
• P0330
• P0335
• P0336
• P0340
• P0410
• P0411
• P0412
• P0422
• P0440
• P0441
• P0443
• P0446
• P0450
• P0455
• P0501
• P0506
• P0507
• P0560
• P1112
• P1113
• P1502
• P1740
• CLEARING DIAGNOSTIC TROUBLE CODES (DTC)

Engine Control System - Tests W/codes Cadillac Catera I

INTRODUCTION

DIAGNOSTIC SYSTEM

Hard Failures

Intermittent Failures

DTC INFO MODE

DTC STATUS

FAIL THIS IGN.

HISTORY

LAST TEST FAIL

MIL REQUEST

NOT RUN SCC

TEST FAIL SCC

FAILED SINCE CLEAR

NOT RUN SINCE CL.

NOT RUN THIS IGN.

TEST RAN AND PASSED

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

POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK

MIL DIAGNOSIS

DLC DIAGNOSIS OR NO SCAN TOOL DATA

READING TROUBLE CODES

TROUBLE CODE DEFINITION

HARD OR INTERMITTENT TROUBLE CODE DETERMINATION

CLEARING DIAGNOSTIC TROUBLE CODES (DTC)

ECM/PCM/VCM LOCATION

Diagnostic Aids

SPECIAL TOOLS (DIAGNOSTIC)

SCAN TOOL USAGE

SUMMARY

DIAGNOSTIC TROUBLE CODES

DTC P0100 - MAF SENSOR CIRCUIT

Circuit Description

Conditions required to set DTC are

Diagnostic Procedures

DTC P0101 - MAF SENSOR SYSTEM PERFORMANCE

DTC P0110 - IAT SENSOR CIRCUIT

IAT TEMPERATURE-TO-RESISTANCE VALUES

DTC P0115 - ECT SENSOR CIRCUIT

DTC P0116 - ECT SENSOR CIRCUIT PERFORMANCE

ECT TEMPERATURE-TO-RESISTANCE VALUES

DTC P0120 - TP SENSOR CIRCUIT

DTC P0130 - HO2S CIRCUIT BANK 1, SENSOR 1

DTC P0131 - HO2S CIRCUIT LOW VOLTAGE BANK 1, SENSOR 1

DTC P0132 - HO2S CIRCUIT HIGH VOLTAGE BANK 1, SENSOR 1

DTC P0133 - HO2S SLOW RESPONSE BANK 1, SENSOR 1

DTC P0134 - HO2S INSUFFICIENT ACTIVITY BANK 1, SENSOR 1

DTC P0135 - HO2S HEATER CIRCUIT BANK 1, SENSOR 1

DTC P0136 - HO2S CIRCUIT BANK 1, SENSOR 2

DTC P0137 - HO2S CIRCUIT VOLTAGE LOW BANK 1, SENSOR 2

DTC P0138 - HO2S CIRCUIT VOLTAGE HIGH BANK 1, SENSOR 2

DTC P0140 - HO2S INSUFFICIENT ACTIVITY BANK 1, SENSOR 2

DTC P0141 - HO2S HEATER CIRCUIT BANK 1, SENSOR 2

DTC P0150 - HO2S CIRCUIT BANK 2, SENSOR 1

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

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

DTC P0153 - HO2S SLOW RESPONSE BANK 2, SENSOR 1

DTC P0154 - HO2S INSUFFICIENT ACTIVITY BANK 2, SENSOR 1

DTC P0155 - HO2S HEATER CIRCUIT BANK 2, SENSOR 1

DTC P0156 - HO2S CIRCUIT BANK 2, SENSOR 2

DTC P0157 - HO2S CIRCUIT VOLTAGE LOW BANK 2, SENSOR 2

DTC P0158 - HO2S CIRCUIT VOLTAGE HIGH BANK 2, SENSOR 2

DTC P0160 - HO2S INSUFFICIENT ACTIVITY BANK 2, SENSOR 2

DTC P0161 - HO2S HEATER CIRCUIT BANK 2, SENSOR 2

DTC P0171 - FUEL TRIM SYSTEM LEAN, BANK 1

DTC P0172 - FUEL TRIM SYSTEM RICH, BANK 1

DTC P0174 - FUEL TRIM SYSTEM LEAN, BANK 2

DTC P0175 - FUEL TRIM SYSTEM RICH, BANK 2

DTC P0201 - INJECTOR NO. 1 CONTROL CIRCUIT

DTC P0202 - INJECTOR NO. 2 CONTROL CIRCUIT

DTC P0203 - INJECTOR NO. 3 CONTROL CIRCUIT

DTC P0204 - INJECTOR NO. 4 CONTROL CIRCUIT

DTC P0205 - INJECTOR NO. 5 CONTROL CIRCUIT

DTC P0206 - INJECTOR NO. 6 CONTROL CIRCUIT

DTC P0230 - FUEL PUMP CONTROL CIRCUIT

DTC P0300 - ENGINE MISFIRE DETECTED

DTC P0301 - CYLINDER NO. 1 MISFIRE DETECTED

DTC P0302 - CYLINDER NO. 2 MISFIRE DETECTED

DTC P0303 - CYLINDER NO. 3 MISFIRE DETECTED

DTC P0304 - CYLINDER NO. 4 MISFIRE DETECTED