Engine Controls - Tests W/codes - 3.1l Buick Century V

INTRODUCTION

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

If no faults were found while performing BASIC TESTING , proceed with DIAGNOSTIC PROCEDURE under SELF-DIAGNOSTIC SYSTEM. If no fault codes or only a non-running Code 12 is present and driveability problems exist, proceed to TESTS W/O CODES article in this section 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 in this section.

SELF-DIAGNOSTIC SYSTEM

Note. Powertrain Control Module (PCM) is also be referred to as Electronic Control Module (ECM) in some diagnostic charts and figures. Terms are used interchangeably.

Control module is equipped with a self-diagnostic system, which detects system failures or abnormalities. When a malfunction occurs, control module will illuminate SERVICE ENGINE SOON light located on instrument panel. SERVICE ENGINE SOON light is also be referred to as the Malfunction Indicator Light (MIL). When malfunction is detected and light is turned on, a corresponding trouble code will be stored in control module memory. To retrieve stored codes, see RETRIEVING CODES (NON-SCAN) . Malfunctions are recorded as hard failures or as intermittent failures.

HARD FAILURES

Hard failures cause SERVICE ENGINE SOON light to glow and remain on until malfunction is repaired. If light comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined using diagnostic (code) charts. If a sensor fails, control module will use a substitute value in its calculations to continue engine operation. In this condition, vehicle is functional, but it will most likely encounter degraded driveability.

INTERMITTENT FAILURES

Intermittent failures cause SERVICE ENGINE SOON light to flicker or glow and go out about 10 seconds after intermittent fault goes away. Corresponding trouble code, however, will be retained in control module memory. If related fault does not reoccur within 50 engine starts, related 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 in this section.

DIAGNOSTIC PROCEDURE

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

1. Ensure all engine systems not related to computer system are operating properly. DO NOT q proceed with testing unless all other problems have been repaired. DIAGNOSTIC CIRCUIT CHECK must be performed before using trouble code charts. See «BASIC TESTING»(/buick/century/v-1982-1996/remont/testing-diagnostics/#engine-controls-basic-testing) article in this section.
2. If trouble codes were displayed (other than Code 12), determine whether codes are hard or intermittent trouble codes. Hard codes will cause SERVICE ENGINE SOON light to glow continuously while engine is running. See «HARD OR INTERMITTENT TROUBLE CODE DETERMINATION»(/buick/century/v-1982-1996/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__hard-or-intermittent-trouble-code-determination) . For diagnosing hard codes, proceed to appropriate trouble code chart. For diagnosing intermittent codes, proceed to INTERMITTENTS in «TESTS W/O CODES»(/buick/century/v-1982-1996/remont/testing-diagnostics/#engine-controls-tests-wo-codes) article in this section.
3. If no trouble codes are present and a driveability problem exists, refer to SYMPTOMS in «TESTS W/O CODES»(/buick/century/v-1982-1996/remont/testing-diagnostics/#engine-controls-tests-wo-codes) article in this section. Doing so will help identify proper system or component to check in «SYSTEM/COMPONENT TESTS - 3.1L»(/buick/century/v-1982-1996/remont/testing-diagnostics/#engine-controls-systemcomponent-tests-31l) article in this section.
4. After necessary repairs are made, clear trouble codes and perform FIELD SERVICE MODE CHECK in «BASIC TESTING»(/buick/century/v-1982-1996/remont/testing-diagnostics/#engine-controls-basic-testing) article in this section.

Note. For information on retrieving codes using a scan tester, refer to user and reference manuals supplied with tester.

RETRIEVING CODES (NON-SCAN)

Note. On models using a 12-terminal DLC (previously referred to as the ALDL), if a wire is present at terminal "B", inserting a jumper wire into test and ground terminals of DLC with engine running will cause fuel injected vehicles to enter field service mode. Flashes of SERVICE ENGINE SOON light will not indicate codes if this is done. See FIELD SERVICE MODE CHECK in BASIC TESTING article in the ENGINE PERFORMANCE section. On models not using a 12-terminal DLC or not having a wire present in terminal "B", codes must be retrieved using a hand-held scan tester.

DATA LINK CONNECTOR (DLC) TEST TERMINALS

1. Turn ignition on. DO NOT start engine. SERVICE ENGINE SOON light should glow. Locate DLC attached to control module wiring harness. Most DLC's are located under dash on driver side of vehicle. For exact location of DLC, refer to COMPONENT LOCATIONS in «SYSTEM/COMPONENT TESTS - 3.1L»(/buick/century/v-1982-1996/remont/testing-diagnostics/#engine-controls-systemcomponent-tests-31l) article in this section. Insert jumper wire from terminal "B" (diagnostic test terminal) to terminal "A" (ground) of DLC. (Scheme 3)
2. SERVICE ENGINE SOON light should begin to flash codes. Each code will be repeated 3 times. If codes are not flashed or SERVICE ENGINE SOON light does not glow, perform DIAGNOSTIC CIRCUIT CHECK in «BASIC TESTING»(/buick/century/v-1982-1996/remont/testing-diagnostics/#engine-controls-basic-testing) article in this section. To exit diagnostic mode, turn ignition off and remove jumper wire from DLC connector.

Scheme 3

READING TROUBLE CODES

Control module stores component failure information under a related trouble code which can be recalled for diagnosis and repair. Trouble codes may be read by counting flashes of SERVICE ENGINE SOON light or by reading digital display on a scan tester. Scan tester is faster to use, more accurate and capable of reading information which otherwise would necessitate testing individual control module and sensor/solenoid connector terminals using a digital voltmeter. See SCAN TESTER USAGE and SCAN DATA.

Note. When using most scan testers, a time delay exists between serial data updates. For instantaneous response, a digital voltmeter must be used.

If scan tester is not available, reading flashes of SERVICE ENGINE SOON light is possible by grounding diagnostic test terminal "B" (if a wire is present) of DLC with ignition on and engine off. (Scheme 3) For example, "FLASH, FLASH, pause, FLASH, longer pause" identifies Code 21. First series of flashes is first digit of trouble code. Second series of flashes is second digit of trouble code. Trouble codes are displayed starting with lowest numbered code. Each code is displayed 3 times. Codes will continue to repeat as long as DLC test terminal is grounded.

Note. Trouble codes will be recorded at various operating times. Some codes require operation of that sensor or switch for 5 seconds; others require operation for 5 minutes or longer at normal operating temperature, vehicle speed and load. Therefore, some codes may not set in a service bay operational mode and may require road testing vehicle in order to duplicate condition under which code will set.

TROUBLE CODE DEFINITION

PCM TROUBLE CODE CONVERSION (1)

Note. Use trouble code charts only if SERVICE ENGINE SOON light is illuminated (indicating a current problem exists).

HARD OR INTERMITTENT TROUBLE CODE DETERMINATION

During any diagnostic procedure, determine if codes are hard failure codes or intermittent failure codes. Diagnostic charts will not usually help analyze intermittent codes. To determine hard codes and intermittent codes

1. Enter diagnostic mode. Read and record all stored trouble codes. Exit diagnostic mode, and clear trouble codes. See «CLEARING TROUBLE CODES»(/buick/century/v-1982-1996/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__clearing-trouble-codes) .
2. Apply parking brake, and place transmission in Neutral or Park. Block drive wheels, and start engine. SERVICE ENGINE SOON light should go out. Run warm engine at specified curb idle for 2 minutes and note SERVICE ENGINE SOON light.
3. If SERVICE ENGINE SOON light comes on, enter diagnostic mode. Read and record trouble codes. This will reveal hard failure codes. Oxygen sensor related codes may require a road test to reset hard failure after trouble codes were cleared.
4. If SERVICE ENGINE SOON light does not come on, all stored trouble codes were intermittent failures, except as noted above.

CLEARING TROUBLE CODES

Note. On models not utilizing a 12-terminal DLC or if no wire is present in terminal "B", codes are cleared using a scan tester.

Turn ignition switch to ON position, and ground diagnostic test terminal "B" at DLC. (Scheme 3) Turn ignition switch to OFF position, and remove control module fuse from fuse block for 10 seconds. Replace fuse. Remove diagnostic terminal ground lead. If fuse cannot be located, pigtail at battery can be disconnected. When power to ECM is remove, degraded driveability may be exhibited until control module "relearns" optimum operational parameters.

ECM/PCM LOCATION

On most models, engine control module is located behind right or left side of dash or behind right or left kick panel. See COMPONENT LOCATIONS in SYSTEM/COMPONENT TESTS - 3.1L article in this section.

Diagnostic Aids

Diagnostic aids (located in many trouble code charts) 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.

Field Service Mode Check (If Available)

If DLC test terminal "B" is grounded with engine running, SERVICE ENGINE SOON light will indicate operational mode of engine. This test confirms proper operation of fuel system and verifies "closed loop" operation. Clear codes and perform this test after any repair is completed. Some models require the use of a scan tester to enter field service mode. Field service mode check can be found by proceeding to FIELD SERVICE MODE CHECK in BASIC TESTING article in this section.

SPECIAL TOOLS (DIAGNOSTIC)

Note. A scan tester plugged into DLC may be used to read trouble codes and check voltages in system on serial data line (terminal "E", or terminal "M"). This can save a great deal of time. For additional information, see SCAN TESTER USAGE and SCAN DATA.

Computerized engine control system is most easily diagnosed using scan tester; however, other tools may aid in diagnosing problems if a scan tester is unavailable. These tools are a tachometer, test light, ohmmeter, digital voltmeter with 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 chart.

SCAN TESTER USAGE

Note. Before connecting scan tester to vehicle, diagnostic system should be checked to determine if system is operating properly and if information received will be accurate. This is done by performing DIAGNOSTIC CIRCUIT CHECK located in BASIC TESTING article in this section. If vehicle does not pass diagnostic circuit check, information received may be invalid.

Scan tester 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 tester cuts down diagnostic time dramatically by furnishing input data (voltage signals) which can be compared to specification parameters. See SCAN DATA. They may also furnish information on output device (solenoids and motors) status. However, status parameters only indicate output signals have been sent to devices by control module; they do not indicate whether devices have responded properly to signal. Verify proper response at output device using a voltmeter or test light. Vehicles utilizing a 16-terminal DLC or 12-terminal DLC with terminal "B" not used, must use a scan tester for retrieving codes or enter Field Service Mode.

Note. Code 12 should always exist when DLC terminal "B" is grounded with key on and engine not running, but it may not be indicated by all makes of scan testers.

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

Using a scan tester is the easiest method of checking sensor specifications and other data parameters. Tester 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, turn ignition off, remove tester, turn ignition on and ground DLC test terminal "B". Same codes flashed by SERVICE ENGINE SOON light should be indicated by scan tester.

SCAN DATA

Note. Information contained in following tables is typical of readings taken on vehicle with engine idling, upper radiator hose hot, closed throttle, transmission in Park or Neutral, "closed loop" status achieved and all accessories off (except as noted in tables). Data parameters are updated a minimum of every 1 1/4 seconds. On systems using P-4 computers, parameter updates are more frequent. Not all devices and systems are used on all models; following lists only represent most commonly used parameters. For additional information, refer to owner manual furnished with tester.

MULTIPORT FUEL INJECTION (MFI)

ECM/PCM CODE CHARTS

Note. In following diagnostic tests, schematics and illustrations are courtesy of General Motors Corp.

CODE P0101, MAF SENSOR CIRCUIT

The Mass Air Flow (MAF) sensor measures the flow of air which passes through it in a given time. PCM uses this information to monitor the operating condition of the engine for fuel delivery calculations. A large quantity of air movement indicates acceleration, while a small quantity indicates deceleration or idle. MAF sensor produces a frequency signal, which cannot be easily measured. Diagnose sensor using procedures on this chart.

Code P0101 will set when the following conditions are present.

1. Engine is running.
2. No MAF signal for over 4 seconds.

With Code P0101 set, PCM will use a default value for airflow based on throttle position, IAC motor position and engine speed. PCM will illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. This step checks to see if PCM recognizes a problem.
2. Voltage reading at sensor harness terminal "A" of less than 4 volts or greater than 6 volts indicates a fault in circuit No. 492 (Yellow wire), or poor connection.
3. Verifies that both ignition feed voltage and a good ground circuit are available.

An intermittent may be caused by a poor connection, mis-routed harness, rubbed through wire insulation or a wire broken inside the insulation. Check for

1. Poor Connection At PCM pin Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
2. Mis-Routed Harness Inspect MAF sensor harness to ensure it is not too close to high voltage wires, such as spark plug wires.
3. Damaged Harness Inspect harness for damage. If harness appears okay, observe Tech-1 while moving related connectors and wiring harness. A change in display would indicate intermittent fault location.
4. Plugged Air Intake Filter A wide-open throttle acceleration from a stop should cause MAF reading on Tech-1 to range from approximately 4-7 grams per second at idle to 100 or greater at time of 1-2 shift. If not, check for restriction.

Code P0101 Schematic (3.1L) MAF Sensor Circuit. Scheme 4

Code P0101 Flow Chart (3.1L) MAF Sensor Circuit. Scheme 5

CODE P0112, IAT SENSOR CKT LOW TEMPERATURE INDICATED

The Intake Air Temperature (IAT) sensor is a thermistor. PCM applies and monitors 5 volts to sensor. When air is cold, sensor resistance is high and PCM will measure a high signal voltage. If air is warm, sensor resistance is low causing PCM to measure low voltage. Code P0112 will set when the following conditions are present.

1. Engine coolant temperature is greater than 140°F (60°C).
2. Mass air flow is less than 12 grams per second.
3. Vehicle speed is less than 25 MPH.
4. IAT signal voltage indicates an intake air temperature less than -29°F (-34°C) for 5 seconds.

With Code P0112 set, PCM will substitute a default value of 61°F (16°C) for intake air temperature. Code P0112 does not illuminate the Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. An open sensor, wire or connection will cause Code P0112 to set. An open circuit would cause Tech-1 to display approximately -40°F (-40°C). This test determines if wiring and PCM are okay.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for

1. Poor Connection Or Damaged Harness

Inspect PCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.

1. Intermittent Test

Observe IAT on Tech-1 while moving related connectors and wiring harness with warm engine running. If failure is induced, IAT display will change to a -40° temperature reading. This may assist in isolating the location of the malfunction.

Code P0112 Schematic (3.1L) IAT Sensor Ckt Low Temperature Indicated. Scheme 6

Code PO112 Flow Chart (3.1L) IAT Sensor Ckt Low Temperature Indicated. Scheme 7

CODE P0113, IAT SENSOR CKT HIGH TEMPERATURE INDICATED

The Intake Air Temperature (IAT) sensor is a thermistor. PCM applies and monitors 5 volts on circuit to sensor. When air is cold, sensor resistance is high and PCM will measure a high signal voltage. If air is warm, sensor resistance is low causing PCM to measure low voltage.

Code P0113 will set when the following conditions are present.

1. Signal voltage indicates an intake air temperature greater than 284°F (140°C).
2. Vehicle speed is greater than 35 MPH.
3. Above conditions are met for at least for 5 seconds.

With Code P0113 set, PCM will use a default value of 61°F (16°C) for intake air temperature. Code P0113 does not illuminate the Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. Tech-1 may be used to diagnose this fault since PCM transmits actual values when the fault is present. A grounded circuit will cause Tech-1 to display a temperature of approximately 297°F (147°C).
2. If Tech-1 displays -40° with IAT sensor disconnected, PCM and wiring are okay. Replace IAT sensor.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for

1. Poor Connection Or Damaged Harness Inspect PCM harness for short to ground in circuit No. 472 (Tan wire), improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.
2. Intermittent Test Observe IAT on Tech-1 while moving related connectors and wiring harness with warm engine running. If failure is induced, IAT display will change to a 297°F (147°C) temperature reading. This may assist in isolating the location of the malfunction.

Code P0113 Flow Chart (3.1L) IAT Sensor Circuit High Temperature Indicated. Scheme 8

CODE P0117, COOLANT TEMP SENSOR LOW TEMP INDICATED

ECT sensor uses a thermistor to control signal voltage to PCM. PCM applies and monitors a 5 volts to ECT sensor. When engine coolant is cold, sensor (thermistor) resistance is high and PCM will sense a high signal voltage. As engine coolant warms up, sensor resistance becomes less and PCM voltage drops. With Code P0117 set, PCM will turn cooling fans on and use a default engine coolant temperature value based on run time. PCM will illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. Code 14 reference applies to 5.7L "Y" body only. This step determines if conditions necessary to set Code P0117 exist.
2. Determines if circuit is shorted to ground.

Tech 1 displays engine temperature in degrees Celsius (°C) and Fahrenheit (°F). After engine is started, temperature should rise steadily to 194°F (90°C), then stabilize when thermostat opens. An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for

1. Poor Connection Or Damaged Harness Inspect PCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.
2. Intermittent Test Using Tech 1, monitor engine coolant temperature while moving related connectors and wiring harness. If failure is induced, display will change. This may assist in isolating the location of the malfunction.
3. Shifted Sensor See TEMPERATURE-TO-RESISTANCE VALUES table to test ECT sensor at various temperature levels to evaluate the possibility of a shifted (mis-scaled) sensor which may result in driveability complaints.
4. A faulty connection, or an open in sensor circuits will cause Code P0117 to set.

TEMPERATURE-TO-RESISTANCE VALUES (1)

Code P0117 Flow Chart (3.1L) Coolant Temperature Sensor Low Temperature Indicated. Scheme 9

CODE P0118, COOLANT TEMP SENSOR HIGH TEMP INDICATED

ECT sensor uses a thermistor to control signal voltage to PCM. PCM applies and monitors a 5 volts to ECT sensor. When engine coolant is cold, sensor (thermistor) resistance is high and PCM will sense a high signal voltage. As engine coolant warms up, sensor resistance becomes less and PCM voltage drops. With Code P0118 set, PCM will turn cooling fans on and use a default engine coolant temperature value based on run time. PCM will illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. Code 15 reference applies to 5.7L "Y" body only. This step determines if conditions necessary to set Code P0118 exist.
2. This test will determine if signal circuit is shorted to ground which will cause conditions for Code P0118.
3. This test will determine if circuit is open. If circuits are okay, check connections at PCM and ECT sensor.

Tech 1 displays engine temperature in degrees Celsius (°C) and Fahrenheit (°F). After engine is started, temperature should rise steadily to 194°F (90°C), then stabilize when thermostat opens. An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check the following for

1. A short to ground in circuit No. 410 (Yellow wire).
2. Intermittent Test Using Tech 1, monitor engine coolant temperature while moving related connectors and wiring harness. If failure is induced, display will change. This may assist in isolating the location of the malfunction.
3. Shifted Sensor See TEMPERATURE-TO-RESISTANCE VALUES table to test ECT sensor at various temperature levels to evaluate the possibility of a shifted (mis-scaled) sensor which may result in driveability complaints.

TEMPERATURE-TO-RESISTANCE VALUES (1)

Code P0118 Flow Chart (3.1L) Coolant Temperature Sensor High Temperature Indicated. Scheme 10

CODE P0122, THROTTLE POSITION SENSOR SIGNAL VOLTAGE LOW

The Throttle Position (TP) sensor provides a voltage signal that changes relative to throttle blade angle. Signal voltage will vary from .20-.74 volt at idle to greater than 4 volts at Wide Open Throttle (WOT). TP sensor signal is one of the most important inputs used by PCM for fuel control and for most of the PCM control outputs.

Code P0122 will set when the following conditions are present.

1. Ignition on.
2. TP sensor signal voltage is less than .2 volt for a precalibrated time.

With Code P0122 set, Tech 1 will continue to display the actual throttle sensor voltage, but ignore TP signal and read mass air flow value for other PCM controlled functions, PCM will not allow 4th gear, TCC or cruise control operation, 1st, 2nd, and 3rd allowed. PCM will illuminate Malfunction Indicator Light (MIL). If signal circuit is open or grounded when engine is started, a high idle may occur. Tech 1 may read as follows with signal open or grounded.

1. TP equals .2 volt or less.
2. MIL is illuminated.
3. Code P0122 is set. NOTE: Test numbers refer to numbers on diagnostic chart.

1. Determines if conditions necessary to set Code P0122 exist.
2. Simulates Code P0123 (high voltage). If PCM recognizes high signal voltage and sets Code P0123, PCM and wiring are okay.
3. Simulates a high signal voltage. Checks signal circuit for an open.

Tech 1 displays throttle position in volts. Voltage should increase steadily as throttle is moved toward WOT.

An open or short to ground in reference and signal circuits will cause Code P0122 to set. Check for

1. Poor Connection Or Damaged Harness Inspect PCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.
2. Intermittent Test Monitor TP sensor voltage display on Tech 1 while moving related connectors and wiring harness. If failure is induced, display will change. This may assist in isolating the location of the malfunction.
3. TP Sensor Scaling Observe TP sensor voltage display while depressing accelerator pedal with engine stopped and ignition Display should vary from closed throttle TP sensor voltage when throttle is closed (.20-.74 volt) to greater than 4 volts when throttle is held at WOT position.

Code P0122 Flow Chart (3.1L) Throttle Position Sensor Signal Voltage Low. Scheme 11

CODE P0123, THROTTLE POSITION SENSOR SIGNAL VOLTAGE HIGH

The Throttle Position (TP) sensor provides a voltage signal that changes relative to throttle blade angle. Signal voltage will vary from .20-.74 volt at idle to approximately 5 volts at Wide Open Throttle (WOT). TP sensor signal is one of the most important inputs used by PCM for fuel control and for most of the PCM control outputs.

Code P0123 will set when the following conditions are present.

1. TP sensor voltage is greater than 4.8 volts at any time, or engine is running and air flow is less than 17 grams per second.
2. Engine speed is greater than 600 RPM.
3. TP sensor signal voltage is greater than 1.06 volts.
4. Code P0101 is not present.
5. All conditions are met for 5 seconds.

With Code P0123 set, Tech 1 will continue to display the actual throttle sensor voltage, but ignore TP signal and read mass air flow value for other PCM controlled functions, PCM will not allow 4th gear, TCC or cruise control operation, 1st, 2nd, and 3rd allowed. PCM will illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. With closed throttle, ignition on, or at idle, voltage at PCM TP sensor signal circuit should be .20-.74 volt.
2. With TP sensor disconnected, TP sensor voltage should decrease and Code P0122 will set. This test verifies that PCM and wiring are okay.
3. Probing ground circuit with a test light check sensor ground circuit. A faulty sensor ground circuit will cause Code P0123 to set.

Tech 1 displays throttle position in volts. With closed throttle, ignition on, or at idle, voltage should be .20-.74 volt. If voltage is not as specified, replace TP sensor. An open in sensor ground circuit will cause Codes P0112, P0712, P0117 and P0123 to set. Check for

1. Poor Connection Or Damaged Harness Inspect PCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.
2. Intermittent Test Monitor TP sensor voltage display on Tech 1 while moving related connectors and wiring harness. If failure is induced, display will change. This may assist in isolating the location of the malfunction.
3. TP Sensor Scaling Observe TP sensor voltage display while depressing accelerator pedal with engine stopped and ignition on. Display should vary from closed throttle TP sensor voltage when throttle is closed (.20-.74 volt) to greater than 4 volts when throttle is held at WOT position.

Code P0123 Flow Chart (3.1L) Throttle Position Sensor Signal Voltage High. Scheme 12

Code P0123, TPS Signal Voltage High Flow Chart (3.1L). Scheme 13

CODE P0131, HEATED O2 SENSOR LOW SIGNAL VOLTAGE (LEAN)

The PCM supplies and monitors a voltage of approximately .45 volt between PCM HO2S low reference circuit and HO2S signal circuit. If read with a 10-megohm DVOM, voltage may read as low as .32 volt. HO2S varies voltage within a range of approximately 1.0 volt (rich) to .10 volt (lean). Sensor is like an open circuit and produces no voltage when less than approximately 600°F (360°C). Open loop operation is caused by Codes P0131 or P0132, an open sensor circuit, or a cold sensor. Code P0131 will set when the following conditions are present.

1. HO2S signal voltage remains less than .248 volt for at least 4.2 minutes.
2. System is operating in closed loop.

Code P0131 will cause system to operate in open loop. PCM will illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. Running engine at 1200 RPM keeps oxygen sensor hot to ensure oxygen sensor remains active and can read exhaust oxygen content accurately.
2. Opening HO2S signal circuit and grounding HO2S low circuit should result in a displayed voltage between .35-.55 volt. If display is still fixed less than .35 volt, fault is a short to ground in signal circuit, or faulty PCM.

Using Tech 1, observe LT fuel trim values at different RPM and air flow conditions. Tech 1 also displays fuel trim cells allowing LT fuel trim values to be checked in each cell, determining when Code P0131 may have been set. LT fuel trim values will be around 158 or greater if conditions exist for Code P0131 to set.

1. Heated Oxygen Sensor Wire Sensor pigtail may be mispositioned and contacting exhaust manifold.
2. Check for intermittent ground in wire between connector and sensor.
3. Poor PCM to engine block ground.
4. MAF Sensor System will go lean when MAF sensor output causes PCM to sense a lower than normal air flow. Disconnect MAF sensor. If lean condition no longer exists, replace MAF sensor.
5. Lean Injectors Perform injector balance test.
6. Fuel Contamination Water near in-tank fuel pump inlet causing fuel contamination in fuel delivered to injectors. Water causes a lean exhaust and can set Code P0131.
7. Fuel Pressure If pressure is too low, system will be lean. To confirm, monitor fuel pressure while driving at various speeds and/or load conditions.
8. Exhaust Leaks If an exhaust leak above the oxygen sensor is present, outside air may be allowed to be pulled into exhaust stream and flow past sensor.
9. Vacuum Or Crankcase Leak Can cause a lean condition and/or possibly a high idle.
10. If all above components/systems are okay, heated oxygen sensor is faulty.
11. Faulty HO2S Heater or Heater Circuit Refer to DIAGNOSTICS AIDS in Code P0134 chart.

Code P0131 Schematic (3.1L) Heated O2 Sensor Low Signal Voltage (Lean). Scheme 14

Code P0131 Flow Chart (3.1L) Heated O2 Sensor Low Signal Voltage (Lean). Scheme 15

CODE P0132, HEATED O2 SENSOR HIGH SIGNAL VOLTAGE (RICH)

The PCM supplies and monitors a voltage of approximately .45 volt between PCM HO2S low reference circuit and HO2S signal circuit. If read with a 10-megohm DVOM, voltage may read as low as .32 volt. HO2S varies voltage within a range of approximately 1.0 volt (rich) to .10 volt (lean). Sensor is like an open circuit and produces no voltage when less than approximately 600°F (360°C). Open loop operation is caused by Codes P0131, P0132 or P0134, or a cold sensor.

Code P0132 will set when the following conditions are present.

1. HO2S voltage on signal circuit remains greater than .75 volt for at least 2 minutes while in closed loop.
2. Throttle angle is between 6-40 percent.
3. Codes P0122 or P0123 are not set.

Code P0132 will cause system to operate in open loop. PCM will illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if conditions necessary to set Code P0132 exist
2. When grounding circuits, Tech 1 should read less than .35 volt. If display is not as specified, check for short to voltage in signal circuit.

1. Fuel Pressure If pressure is too high, system will be rich. PCM can compensate for some increase. However, Code P0132 will set if pressure gets too high.
2. Rich Injectors Perform injector balance test.
3. Leaking Injectors Check for fuel contaminated oil.
4. EVAP Canister Purge Check for fuel saturation. If full of fuel, check canister control and hoses.
5. MAF Sensor System will go rich when MAF sensor output causes PCM to sense a higher than normal air flow. Disconnecting MAF sensor will allow PCM to set a fixed value for sensor. If rich condition no longer exists, replace MAF sensor.
6. Check for leaking fuel pressure regulator diaphragm by checking vacuum line to regulator for fuel.
7. TP Sensor An intermittent TP sensor output will cause system to go rich due to a false indication of throttle moving.
8. False rich indication due to silicon contamination of heated oxygen sensor. This will be indicated by Code P0131 accompanied by lean driveability conditions and a powdery White deposit on sensor.
9. Heated Oxygen Sensor (HO2S) If HO2S is internally shorted, HO2S voltage displayed on Tech 1 will be greater than 1 volt. Disconnect HO2S with ignition on and engine running. If displayed voltage decreases from greater than 1.0 volt to approximately .45 volt, replace HO2S.
10. Faulty HO2S Heater Or Heater Circuit Refer to DIAGNOSTICS AIDS in Code P0134 chart.

Code P0132 Flow Chart (3.1L) Heated O2 Sensor High Signal Voltage (Rich). Scheme 16

CODE P0134, HEATED OXYGEN SENSOR OPEN CIRCUIT

The PCM supplies and monitors voltage of approximately .45 volt between PCM HO2S low reference circuit (Tan wire) and HO2S signal circuit (Purple wire). If read with a 10 megohm DVOM, voltage may read as low as .32 volt. HO2S varies voltage within a range of approximately 1 volt (rich) to .10 volt (lean). Sensor is like an open circuit and produces no voltage when less than approximately 600°F (360°C). Open loop operation is caused by open oxygen sensor circuit or a cold sensor. Code P0134 will set when the following conditions are present.

1. Engine coolant temperature is greater than 110°F (43°C).
2. Engine run time is more than 40 seconds.
3. HO2S signal voltage is steady between .35-.56 volt.
4. Throttle angle is greater than 3 percent.
5. All conditions are met for approximately 30 or more seconds.

Code P0134 will cause system to operate in open loop. PCM will illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. If conditions necessary to set Code P0132 exist, system will not go into closed loop.
2. This will determine if sensor or wiring is cause of Code P0134.
3. This test checks continuity in reference circuit.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for

1. Poor Connection Or Damaged Harness Inspect PCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.
2. Faulty HO2S Heater Or Heater Circuit With ignition on and engine off, HO2S voltage displayed on Tech 1 should gradually decrease to less than .25 volt, indicating heater is functioning properly. If display does not read as specified, disconnect HO2S and connect test light between terminals "C" and "D". If test light does not light, repair open in suspect wire. If test light lights, replace HO2S.
3. Intermittent Test Using Tech 1, monitor HO2S signal voltage while moving related connectors and wiring harness with engine running at part throttle in closed loop. If failure is induced, HO2S signal voltage reading will change from normal fluctuating voltage (greater than .6 volt and less than .30 volt) to a fixed value of approximately .45 volt. This may assist in isolating the location of the malfunction.

Code P0134 Flow Chart (3.1L) Heated Oxygen Sensor Open Circuit. Scheme 17

CODE P0321, IGNITION CONTROL 24X SIGNAL CIRCUIT ERROR

The 24X Crankshaft Position (CKP) sensor is used to improve idle spark control at low speeds. The 24X CKP is located behind harmonic balancer on front of engine and picks up pulses from reluctor wheel on crankshaft. 24X CKP signal is conditioned by PCM and used to more accurately control spark at lower engine speeds (less than 1200 RPM) where spark control is critical for idle quality.

Code P0321 will set when the following conditions are present.

1. 150 or more 3X reference pulses seen without a 24X signal pulse received.
2. Engine speed is less than 1200 RPM.
3. Engine running.

PCM will disregard 24X sensor input and base timing from 3X low resolution CKP sensor. Code P0321 does not illuminate the Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. 24X signal RPM should be same as engine speed up to about 1200 RPM at which time it stops. This test determines if PCM is putting out a 24X signal.
2. This test determines if signal voltage is present up to PCM.
3. This test determines if 12 volts is present at sensor input.
4. Pigtail and sensor integrity can be determined by applying 12 volts to 24X CKP sensor pigtail circuit.

An intermittent 24X signal error can be caused by poor connections. Ignition feed, reference low and signal circuits should all be checked for poor connections.

Code P0321 Schematic (3.1L) Ignition Control 24X Signal Circuit Error. Scheme 18

Code P0321 Flow Chart (3.1L) Ignition Control 24X Signal Circuit Error. Scheme 19

Code P0321, Ignition Control 24X Signal Ckt Error Flow Chart (3.1L). Scheme 20

CODE P0325, KNOCK SENSOR ERROR

Knock sensor is used to detect engine detonation and allow PCM to retard Ignition Control (IC) timing based on signal being received. The circuitry within knock sensor causes PCM's supplied 5 volts signal to be pulled down, so that under a no knock condition circuit would measure approximately 2.5 volts. Knock sensor produces an AC signal which rides on the 2.5 volts DC voltage. Amplitude and signal frequency is dependent upon the knock level.

If circuit becomes open or shorted to ground, voltage will either become greater than 3.5 volts or less than 1.5 volts. Code P0325 will set if either one of these conditions are present for 20 seconds.

Code P0325 will set when the following conditions are present.

1. Voltage on signal circuit becomes greater than 3.5 volts or less than 1.5 volts.
2. Either condition is present for 20 seconds.

With Code P0325 set, PCM will illuminate Malfunction Indicator Light (MIL) for remainder of the key cycle and retard spark timing (knock retard) by 15 degrees.

Note. Test numbers refer to numbers on diagnostic chart.

1. If Code P0325 is detected, PCM will retard spark timing by 15 degrees. If an audible is heard from engine, repair internal engine problem. Normally no knock should be detected at idle.
2. PCM applies 5 volts through a pull-up resistor which should be present at knock sensor terminal.

Check signal circuit for a intermittent open or short to ground. Also check for proper installation of PROM. If knock sensor circuit is routed too close to secondary ignition wires it may induce a voltage and cause a false knock signal.

Code P0325 Schematic (3.1L) Knock Sensor Error. Scheme 21

Code P0325 Flow Chart (3.1L) Knock Sensor Error. Scheme 22

CODE P0341, CAMSHAFT POSITION SENSOR EXTRA CAM PULSES

During cranking, the Ignition Control Module (ICM) monitors the 3X crankshaft position sensor signal. The 3X signal is used to determine correct cylinder pair to spark first. ICM processes the 3X signal then sends a fuel control reference pulse to PCM. When PCM receives this pulse, all 6 injectors will be commanded to open for one priming shot of fuel in all cylinders. After the priming, injectors remain off for the next 6 fuel control reference pulses from ICM (2 crankshaft revolutions). This allows each cylinder a chance to use the fuel from the priming shot.

During this waiting period, a cam pulse will have been received by PCM. PCM will now begin to operate the injectors sequentially based on true camshaft position. With engine running, PCM monitors cam and fuel control references pulses received and expects to detect 6 fuel control pulses for each cam pulse.

Code P0341 will set when the following conditions are present.

1. Ratio of fuel control pulses to cam pulses does not equal 6.
2. Above condition for 10 occurrences during key cycle.

Code P0341 will illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if conditions necessary to set Code P0341 exist.
2. Determines if fault is in wiring, camshaft sensor or PCM.

Code P0341 indicates an intermittent fault and may not set immediately or under all conditions. Customer comments of symptom experienced may assist in isolating cause of condition. A poor connection or fault in camshaft position sensor circuits, or a faulty camshaft position sensor, may cause PCM to reinitialize injector sequence when fault occurs, causing a possible stumble or miss.

Code P0341 Flow Chart (3.1L) Camshaft Position Sensor Extra Cam Pulses. Scheme 23

CODE P0342, CAMSHAFT POSITION SENSOR CKT (LOSS OF CAM PULSES)

During cranking, the Ignition Control Module (ICM) monitors the 3X crankshaft position sensor signal. 3X signal is used to determine correct cylinder pair to spark first. ICM processes the 3X signal then sends a fuel control reference pulse to PCM. When PCM receives this pulse, all 6 injectors will be commanded to open for one priming shot of fuel in all cylinders. After the priming, injectors remain off for the next 6 fuel control reference pulses from ICM (2 crankshaft revolutions). This allows each cylinder a chance to use the fuel from the priming shot.

During this waiting period, a cam pulse will have been received by PCM. PCM will now begin to operate the injectors sequentially based on true camshaft position. With engine running, PCM monitors cam and fuel control references pulses received and expects to detect 6 fuel control pulses for each cam pulse. Code P0342 will set when the following conditions are present.

1. Cam reference pulses are not detected by PCM for 5 seconds while engine is running.
2. Code P0342 is looking for loss of cam pulses.

PCM will pulse injectors sequentially though possibly not in the correct sequence. Code P0342 will illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if conditions necessary to set Code P0342 exist.
2. By repeatedly bumping the starter, camshaft interrupter and camshaft position sensor will align with each other. At this point, voltage from sensor applied to PCM should temporarily decrease to near zero. This indicates that camshaft position sensor is capable of sending a signal to PCM.
3. Inspect camshaft position sensor for proper installation before replacement.

An intermittent cam reference signal can be caused by poor connections, cracked sensor or internal engine problem.

Code P0342 Flow Chart (3.1L) Camshaft Position Sensor Circuit (Loss Of CAM Pulses). Scheme 24

CODES P0501/P0502, VSS CIRCUIT

The Vehicle Speed Sensor (VSS) in transaxle provides vehicle speed information to PCM. Voltage level and number of pulses increase with vehicle speed. PCM converts the pulsing voltage to MPH, and the MPH can be displayed using a Tech 1.

The function of the VSS buffer, used in past models, has been incorporated into PCM. PCM supplies necessary signal for instrument cluster (4004 pulses per mile) for operating speedometer and odometer.

Code P0501 will set when the following conditions are present.

1. Engine is running.
2. Code P0703 is not set.
3. Transmission is out of Park or Neutral for more than 4 seconds.
4. Vehicle speed is greater than 18 MPH.
5. Brake is not applied.
6. All conditions are met for 2 seconds.

Code P0502 will set when the following conditions are present.

1. Vehicle speed goes from less than 3 to zero MPH in less than 2 seconds, brake not applied.
2. Engine is running.
3. Engine speed is greater than 3000 RPM.
4. Transmission is out of Park or Neutral for more than 4 seconds.

With Codes P0501 or P0502 set, cruise control operation will not be allowed. Code will remain set for remainder of that ignition cycle, and PCM will command only 2nd and 3rd gear based on RPM and TP sensor. TCC will not be allowed to engage. Instrument cluster speedometer may be inoperative. Codes P0501 and P0502 will illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. VSS signal generator only produces a signal if drive wheels are turning greater than 3 MPH.
2. Check PROM for correct application before replacing PCM.

When vehicle is moving greater than 3 MPH, Tech 1 should indicate a vehicle speed. Code P0502 indicates an intermittent and may not set immediately or under all conditions. Check sensor circuits for proper connections. Ensure they are clean and tight and harness is correctly routed.

Code P0501/P0502 Schematic (3.1L) VSS Circuit. Scheme 25

Code P0501/P0502 Flow Chart (3.1L) VSS Circuit. Scheme 26

CODE P0703, TCC BRAKE SWITCH INPUT

PCM monitors status of TCC brake switch input. Code P0703 will set when the following conditions are present.

1. Code P0501 is not present.
2. Vehicle speed has been greater than 35 MPH for 10 seconds and back to zero MPH 5 times.
3. TCC brake switch input status has not changed from released to applied, or applied to released as displayed on Tech 1.

When Code P0703 is set, PCM will not allow 4th gear, cruise control or TCC operation. Code P0703 does not illuminate the Malfunction Indicator Light (MIL).

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for

1. Poor Connection Or Damaged Harness Inspect PCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
2. Intermittent Test Monitor Tech 1 while moving related connectors and wiring harness. If failure is induced, scan data will change from released to applied, or applied to released. This may assist in isolating the location of the malfunction.

Code P0703 Schematic (3.1L) TCC Brake Switch Input. Scheme 27

Code P0703 Flow Chart (3.1L) TCC Brake Switch Input. Scheme 28

CODE P0705, TRANSAXLE RANGE SWITCH

Transmission range switch is part of Transmission Mounted Neutral Start Switch (TMNSS) mounted on transaxle assembly. Transmission range switch is a multi-signal switch that sends information, relative to gear selector position, to PCM. PRNDL input consists of 4 discrete circuits to pull 4 PCM voltages low in various combinations to indicate each gear range. Voltage level of each of the circuits is represented as low equals grounded circuit and high equals open circuit. The 4 states displayed represent decoder parity, "A", "B"and "C" respectively.

Code P0705 will set when the following conditions are present.

1. Ignition is on and engine off.
2. Vehicle speed is zero MPH.
3. PRNDL inputs indicate a gear other than Park and Neutral.
4. All conditions are met for a predetermined time for 3 consecutive start-ups. Or
5. PRNDL inputs status indicators ("P", "A", "B"and "C") indicate an incorrect combination of low and high. PCM will also command stepper motor cruise control to be inhibited.

Code P0705 will cause PCM to command a drive-4 shift position. Code P0705 does not illuminate the Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. This step checks for proper operation of transmission range switch.
2. This test checks for an open or grounded circuit. When Code P0705 is present, PCM assumes drive-4 position until a correct combination is received by PCM. Some gear select positions may not be possible until fault is repaired.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for

1. Poor Connection Or Damaged Harness Inspect PCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
2. Intermittent Test Monitor Tech 1 while moving related connectors and wiring harness. If failure is induced, scan data will change from low to high, or high to low. This may assist in isolating the location of the malfunction.

Code P0705 Schematic (3.1L) Transaxle Range Switch. Scheme 29

Code P0705 Flow Chart (3.1L) Transaxle Range Switch. Scheme 30

CODE P0712, TRANSAXLE TEMP SENSOR LOW TEMP INDICATED

Transaxle temperature sensor uses a thermistor to vary signal voltage to PCM according to temperature. PCM applies and monitors a voltage to sensor. When transaxle fluid is cold sensor resistance is high. Thus, PCM will monitor a high signal voltage. As transaxle fluid warms, sensor resistance becomes less and voltage drops. At normal operating temperature of 68°F-194°F (20°C-90°C) transaxle temperature signal will measure approximately 2-4 volts.

Code P0712 will set when the following conditions are present.

1. Engine run time is over 2 minutes.
2. Transaxle temperature sensor signal indicates a temperature less than -40°F (-40°C).
3. Above conditions for over 1.6 second.

With Code P0712 set, PCM will substitute coolant sensor temperature value for transaxle temperature. Tech 1 will continue to display actual transaxle sensor value. Code P0712 does not illuminate the Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if conditions necessary to set Code P0712 exist.
2. Simulates conditions to set Code P0713. If PCM recognizes low signal voltage and sets Code P0713, wiring and PCM are okay.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for

1. Poor Connection Or Damaged Harness Inspect PCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
2. Intermittent Test Monitor Tech 1 while moving related connectors and wiring harness. If failure is induced, scan data will change from low to high, or high to low. This may assist in isolating malfunction.
3. Shifted Sensor See TEMPERATURE-TO-RESISTANCE VALUES table to test sensor at various temperature levels to evaluate the possibility of a shifted sensor which may result in driveability complaints.
4. A faulty connection, or an open in sensor circuits will cause Code P0117 to set.

TEMPERATURE-TO-RESISTANCE VALUES (1)

Code P0712 Flow Chart (3.1L) Transaxle Temperature Sensor Low Temperature Indicated. Scheme 31

CODE P0713, TRANSAXLE TEMP SENSOR HIGH TEMP INDICATED

Transaxle temperature sensor uses a thermistor to vary signal voltage to PCM according to temperature. PCM applies and monitors a voltage to sensor. When transaxle fluid is cold sensor resistance is high. Thus, PCM will monitor a high signal voltage. As transaxle fluid warms, sensor resistance becomes less and voltage drops. At normal operating temperature of 68°F-194°F (20°C-90°C) transaxle temperature signal will measure approximately 2-4 volts.

Code P0713 will set when the following conditions are present.

1. Engine run time is over 1 minute.
2. Transaxle temperature sensor signal indicates a temperature greater than 284°F (140°C).
3. Above conditions for over 1.6 second.

With Code P0713 set, PCM will substitute ECT sensor value for transaxle temperature. Tech 1 will continue to display actual transaxle sensor value. Code P0713 does not illuminate the Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if conditions necessary to set Code P0713 exist.
2. This test determines if input circuit is shorted to ground which will cause conditions necessary for Code P0713.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for

1. Poor Connection Or Damaged Harness Inspect PCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
2. Intermittent Test Monitor Tech 1 while moving related connectors and wiring harness. If failure is induced, scan data will change from low to high, or high to low. This may assist in isolating malfunction.
3. Shifted Sensor See TEMPERATURE-TO-RESISTANCE VALUES table to test sensor at various temperature levels to evaluate the possibility of a shifted (mis-scaled) sensor which may result in driveability complaints.

TEMPERATURE-TO-RESISTANCE VALUES (1)

Code P0713 Flow Chart (3.1L) Transaxle Temperature Sensor High Temperature Indicated. Scheme 32

Code P0713, Transaxle Temp Sensor High Temp Indicated Flow Chart (3.1L). Scheme 33

CODE P0740, TORQUE CONVERTER CLUTCH

The Torque Converter Clutch (TCC) eliminates the loss of power to torque converter when cruise control is engaged. This allows the convenience of the automatic and the fuel economy of a manual transaxle. The main components of the system are 2 PCM controlled solenoids located inside the transaxle.

TCC is applied when the TCC apply solenoid coil is activated (on) resulting in a straight through mechanical coupling from engine to wheels. TCC is released when TCC apply solenoid coil is deactivated (off) allowing torque converter to operate in conventional manner (fluid coupling between engine and transaxle).

TCC PWM solenoid is used to vary hydraulic pressure to converter clutch regulator valve, allowing a smoother engagement of converter clutch.

Code P0740 will set when the following conditions are present.

1. TP sensor throttle angle greater than 10 percent.
2. Vehicle is in 3rd or 4th gear.
3. VSS signal greater than 35 MPH for a 10 second minimum.
4. TCC is commanded on by PCM.
5. Engine RPM/vehicle speed ratio indicates TCC is not locked.
6. Above conditions for over 10 seconds.

With Code P0740 set, PCM will not allow 4th gear and TCC operation, only 1st, 2nd, and 3rd gear operation. Code P0740 does not illuminate the Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines whether fault is caused by a bad solenoid or control circuit.
2. Checks availability of battery voltage.
3. Checks PCM's ability to pulse PWM solenoid on and Off.

Tech 1 only indicates when PCM has commanded TCC driver on, this does not confirm that TCC is actually engaged. Road test vehicle to determine if TCC is properly functioning. Engine RPM should decrease when Tech 1 indicates TCC has been turned on. If diagnosis indicates all electrical circuits and components are okay, check for hydraulic and mechanical problems.

Code P0740 Flow Chart (3.1L) Torque Converter Clutch. Scheme 34

Code P0740, Torque Converter Clutch Flow Chart (3.1L). Scheme 35

CODE P0755, TRANSMISSION SHIFT SOLENOID "B"

The 4T60E is an electronically shifted transaxle. Within the transaxle are 4 solenoids for shift and TCC control. Solenoid "A" is energized for 1st and 4th gear operation. Solenoid "B" is energized for 1st gear as well as 2nd gear operations. The other 2 solenoids are for TCC operation. This diagnostic chart deals with shift control solenoids only.

When ignition is on, both solenoids "A" and "B" receive 12 volts. PCM will ground "A" and "B" circuits for 1st gear until a shift to 2nd gear is commanded. When vehicle speed and TP sensor reach calibrated values, PCM will turn off ground for solenoid "A" and 2nd gear is engaged. Further increase in vehicle speed will cause PCM to turn off ground for solenoid "B", engaging 3rd gear. In 3rd gear, both solenoids are de-energized. In 4th gear, only solenoid "A" is energized.

All PRNDL indications are ignored as far as transaxle shifting is concerned except for manual low gear. If PRNDL inputs indicate manual low has been selected, PCM will keep both solenoids "A" and "B" energized until approximately 5400 RPM, when PCM will force a shift by de-energizing solenoid "A". Manual 2nd and manual 3rd are controlled hydraulically within transaxle.

Code P0755 will set when the following conditions are present.

1. Shift "B" is failed in off position, causing transaxle to be in 4th gear and: - Desired gear is 1st. - Throttle angle is greater than 3 percent. - VSS is greater than 5 MPH. - Codes P0122, P0123, P0501 or P0502 are not set. - Engine speed divided by vehicle speed does not indicate 1st gear. - Above conditions for 3.5 seconds.

Or

1. Shift "B" is failed in on position, causing transaxle to be in 1st gear and: - Desired gear is 4th. - PRNDL is in 3rd 0r 4th. - Throttle angle is greater than 10 percent. - Codes P0122, P0123 or P0705 are not set. - Engine speed divided by vehicle speed does not indicate 4th gear (LV8 less than 80). - Above conditions for 2 seconds.

When Code P0755 is set, transaxle will be forced into 3rd gear and will not allow TCC. If Code P0755 is set due to a grounded "B" solenoid circuit, only 1st, 2nd and 3rd gear operation will be available. If circuit is open, only 3rd and 4th gear operation will be available. When the fault goes away, normal operation will be available for the balance of the key cycle. Code P0755 does not illuminate the Malfunction Indicator Light (MIL).

Code P0755 Flow Chart (3.1L) Transmission Shift Solenoid "B". Scheme 36

CODE P1350/1361, IC CIRCUIT OPEN

For Code 1361 diagnosis, see CODE 1350/1361 Chart. PCM provides Ignition Control (IC) spark timing on circuit. PCM correctly calculates optimum spark timing based on inputs received from several engine sensors. Engine load is calculated from MAF sensor, engine RPM is derived from the 3X crankshaft position sensor, engine operating temperature from ECT and IAT sensors, and engine knock activity from knock sensor. Other engine functions modify spark to a lesser degree such as TCC engagement and EGR activity.

The by-pass circuit controls an internal switch in the electronic Ignition Control Module (ICM). By-pass circuit will have 5 volts applied to it unless vehicle is in backup spark (base timing mode). This 5 volt signal from PCM allows a solid state switch to direct IC timing pulses to ICM for sequencing and energizing the coil packs. If by-pass circuit is not energized, IC pulses from ICM are shunted to ground, and electronic ICM uses it's own base timing schedule to time and energize the coil packs. Code P1350 will set when the following conditions are present.

1. IC pulses are detected on IC circuit when vehicle is in by- pass (no voltage applied to by-pass should allow IC pulses to be grounded by electronic ICM). Test will either pass or fail within first 100 milliseconds of engine running. If test passes, test will not run until next key cycle.

PCM will allow electronic ICM to control timing using it's own base timing schedule. PCM will illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. For Code 1361 diagnosis, see CODE 1350/1361 chart. This test confirms Code P1350 is present and conditions necessary to set Code P1350 exist.
2. Checks for normal IC ground path through ICM. Code P1350 indicates PCM has detected an open or short to voltage in IC circuit, or a short to voltage in by-pass circuit. An IC circuit shorted to ground will also read less than 500 ohms. However, this should cause Code P1350 to set.

Tech 1 does not have any ability to assist in diagnosis of a Code P1350.

1. EST Line Code P1350 will set if IC circuit is shorted to voltage or open during crank. Code P1350 will also set if by-pass circuit is shorted to voltage during crank.
2. By-pass Line Code P1361 will set during engine run operation if by-pass circuit is shorted to ground or open. Code P1350 will not set if Code P1361 is stored. If Code P1350 is stored, Code P1361 can also set.

Code P1350 Schematic (3.1L) IC Circuit Open. Scheme 37

Code P1350 Flow Chart (3.1L) IC Circuit Open. Scheme 38

Code P1350/1361, IC Circuit Open Flow Chart (3.1L). Scheme 39

CODES P1403/P1404/P1405, EGR ERROR

Codes P1403, P1404 and P1405 are EGR flow test failures. PCM tests the medium and large EGR solenoid valves by cycling each of them on momentarily while monitoring engine RPM. When a solenoid is on, PCM expects to see a drop in engine RPM. Codes P1403, P1404 and P1405 will set when the following conditions are present.

1. Engine coolant temperature is greater than 183°F (84°C).
2. Vehicle is in coast down condition.
3. Vehicle not in decel fuel cutoff.
4. Heated oxygen sensor voltage greater than .57 volt.
5. Vehicle in 1st or 2nd gear.
6. Vehicle speed is greater than 20 MPH.
7. A/C clutch not engaged.
8. RPM 925-1063 (to run EGR No. 1 test).
9. RPM 975-1188 (to run EGR No. 2 test).
10. RPM 1000-1488 (to run EGR No. 3 test).

Code P1403 will set if expected drop is not seen 10 out of 12 times when EGR solenoid No. 1 is tested. Code P1404 will set if expected drop is not seen 9 out of 12 times when medium EGR solenoid No. 2 is tested. Code P1405 will set if expected drop is not seen 4 out of 5 times when large EGR solenoid No. 3 is tested. PCM will illuminate Malfunction Indicator Light (MIL) when codes set.

Note. Test numbers refer to numbers on diagnostic chart.

1. A change in engine RPM should be detected as each solenoid is cycled on.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for

1. Poor Connection Or Damaged Harness Inspect PCM harness connector for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
2. Intermittent Test If connections and harness are okay, monitor a DVOM connected between affected terminal and ground while moving related connectors and wiring harness. If failure is induced, voltage reading will change.
3. Check for a restriction in EGR tube or passage. Also, ensure excessive carbon has not built up on EGR valve orifices.

Note. Check exhaust system for blockage (possibly a plugged converter) if EGR valve shows signs of excessive heat. Repair cause of restricted exhaust system as necessary. Injector open due to following condition may be cause: Stuck, grounded driver circuit or possible faulty PCM. If conditions are not present, oil should be checked for possible fuel contamination.

Code P1403/P1404/P1405 Schematic (3.1) EGR Error. Scheme 40

Code P1403/P1404/P1405 Flow Chart (3.1L) EGR Error. Scheme 41

CODE P1530, A/C REFRIGERANT PRESSURE

A/C refrigerant pressure sensor is located in the high side of A/C cooling system and signals PCM of refrigerant pressure changes. This input indicates how much load A/C compressor is putting on engine. PCM uses this input to determine IAC valve position for idle speed control. This 3 wire sensor has a 5 volts reference input, a signal line and a ground.

When pressure is low, a low signal is sensed at PCM. As pressure rises, voltage increases at PCM which is translated by PCM into a rising pressure. Code P1530 will set if signal voltage remains below a calibrated value, indicating a sensor or circuit failure.

Code P1530 will set when the following conditions are present.

1. Signal voltage sensed at PCM is less than .1 volt for 25.4 seconds when A/C is selected on and engine is running, or signal voltage sensed at PCM is greater than 4.92 volts for 25.4 seconds when A/C is selected on and engine is running. Code P1530 does not illuminate the Malfunction Indicator Light (MIL) and A/C compressor will be disabled. NOTE: Test numbers refer to numbers on diagnostic chart.

1. This step checks voltage signal being received by PCM from A/C pressure sensor.
2. Checks if low voltage signal is from sensor or circuit. Jumpering sensor circuit to 5 volts checks circuit, connections and PCM.
3. This step checks if low signal voltage was due to an open in sensor circuit or 5 volts reference circuit since previous step eliminated pressure sensor.
4. Checks if high voltage signal is from a shorted sensor or a short to voltage in circuit, or ground open. Normally, disconnecting sensor would make a normal circuit go to near zero volt.

Code P1530 sets when signal voltage falls outside normal possible range of sensor and is not due to a refrigerant system problem. If problem is intermittent, check for opens or shorts in harness, or poor connections.

Code P1530 Schematic (3.1L) A/C Refrigerant Pressure. Scheme 42

Code P1530 Flow Chart (3.1L) A/C Refrigerant Pressure. Scheme 43

CODE P1550, CRUISE STEPPER MOTOR

The stepper motor cruise system differs from the up integrated (PCM-controlled) cruise system previously used in that it is a stand-alone system. PCM still retains the ability to disable cruise if conditions are detected which would make cruise control operation undesirable. PCM may inhibit cruise control if the following conditions are present.

1. Engine not running long enough for cruise control operation.
2. Codes P0705 or P1630 set.
3. Engine speed too high or too low.
4. Vehicle speed too high or too low.
5. Transmission range input indicates Park, Neutral, Low or Reverse gear selected.

If PCM detects any of these conditions, it will interrupt the ground at cruise status signal circuit 3.1L to request that cruise control disengage. Code P1550 will set when the following condition is present.

1. Cruise status signal circuit indicates an open or a short to voltage while cruise is engaged and vehicle speed is less than 7 MPH. NOTE: Test numbers refer to numbers on diagnostic chart.

1. Ensures PCM is detecting a current fault.
2. On 3.1L, this ensures cruise status circuit is not open or grounded, or shorted to voltage, and status circuit is being switched on and off by SMCC module.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside insulation. Check for

1. Poor Connection Or Damaged Harness Inspect PCM harness for open or short to voltage in status circuit, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
2. Intermittent Test Observe SMCC status on Tech 1 while moving related connectors and wiring harness with engine running. If failure is induced, SMCC status display will change to engaged. This may assist in isolating the location of the malfunction.
3. On 3.1L, SMCC is a stand-alone system, once software has seen a valid cruise engagement, it has learned cruise is on vehicle.

Code P1550 Schematic (3.1L) Cruise Stepper Motor. Scheme 44

Code P1550 Flow Chart (3.1L) Cruise Stepper Motor. Scheme 45

CODE P1623, PROM ERROR

Check that PROM is correctly inserted in the socket. If okay, replace PROM, clear memory and recheck. If Code P1623 reappears, replace PCM.

Note. To prevent possible electrostatic discharge damage to PCM or PROM, DO NOT touch component leads. DO NOT remove integrated circuit from carrier.

CODE P1630, SYSTEM VOLTAGE HIGH/LOW

PCM monitors system voltage on PCM ignition feed terminal. Code P1630 will set when the following condition is present.

1. PCM detects voltage greater than 17.3 volts or less than 9 volts for more than 10 seconds while engine is running.

With Code P1630 set, transaxle will be forced to 3rd gear and TCC will not be allowed to engage. This is to avoid erratic shifting due to improper voltages. PCM will illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. Test generator output to determine proper operation of voltage regulator. Run engine at moderate speed and measure voltage across battery. If less than 9 volts or greater than 17.3 volts, repair generator.

An intermittent may be caused by a poor connection, rubbed through wire insulation, a wire broken inside insulation or poor PCM grounds. Check for

1. Poor Connection Or Damaged Harness Inspect PCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
2. Intermittent Test Using Tech 1, monitor SYSTEM VOLTS display while moving related connectors and wiring harness. If failure is induced, display will abruptly change. This may assist in isolating the location of the malfunction. An engine stall while manipulating harness indicates PCM has lost voltage at ignition feed terminal (Pink wire). Check for loose connectors in power feed circuit.

Note. Charging with a battery charger while starting engine may set Code P1630.

Code P1630 Schematic (3.1L) System Voltage High/Low. Scheme 46

Code P1630 Flow Chart (3.1L) System Voltage High/Low. Scheme 47

Code P1623, PROM Error Flow Chart (3.1L). Scheme 48

CODE P1640, QDM "A" CIRCUIT

PCM is used to control several components as shown in wiring schematic. PCM controls these devises through use of a Quad-Driver Module (QDM). When PCM is commanding a component on, voltage potential of output circuit will be low (near zero volt). When PCM is commanding output circuit to a component off, voltage potential of circuit will be high (near battery voltage). Primary function of QDM is to supply ground for component being controlled.

Each QDM has a fault line which is monitored by PCM. Fault line signal is available on data stream for scan tool test equipment display on Tech 1. PCM will compare voltage at QDM based on accepted values of fault line. If QDM "A" fault detection circuit senses a voltage other than accepted value, fault line will go from a low signal on data stream to a high signal and Code P1640 will set. Code P1640 will set when the following conditions are present.

1. Engine is running.
2. PCM detects an improper voltage level on a circuit connected to QDM "A".
3. Above conditions met for 5 seconds.
4. If brake is applied, QDM "A" ignores fault.

QDM "A" controls EVAP canister solenoid, fan No. 2 and TCC. PCM will illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. If QDM related code is stored, diagnose that code first. Repair made to related code will repair Code P1640 also.

Monitor voltage at each terminal shown above while moving related harness connectors, including PCM harness. If failure is induced, voltage will change. This may assist in isolating an intermittent condition. Check for bent pins at PCM and PCM connector terminals. If code reoccurs with no apparent connector problem, replace PCM. PCM is protected by an internal circuit breaker. PCM replacement is not necessary after repairing QDM "A" quad-driver controlled circuit or component.

Code P1640 Schematic (3.1L) P1640, QDM "A" Circuit. Scheme 49

Code P1640 Flow Chart (3.1L) P1640, QDM "A" Circuit. Scheme 50

CODE P1650, QDM "B" CIRCUIT

PCM is used to control several components as shown in wiring schematic. PCM controls these devises through use of a Quad-Driver Module (QDM). When PCM is commanding a component on, voltage potential of output circuit will be low (near zero volt). When PCM is commanding output circuit to a component off, voltage potential of circuit will be high (near battery voltage). Primary function of QDM is to supply ground for component being controlled.

Each QDM has a fault line which is monitored by PCM. Fault line signal is available on data stream for scan tool test equipment display on Tech 1. PCM will compare voltage at QDM based on accepted values of fault line. If QDM "B" fault detection circuit senses a voltage other than accepted value, fault line will go from a low signal on data stream to a high signal and Code P1650 will set. Code P1650 will set when the following conditions are present.

1. Engine is running.
2. PCM detects an improper voltage level on a circuit connected to QDM "B".
3. Above conditions met for 5 seconds.

QDM "B" controls transmission shift solenoids "A" and "B", TCC PWM solenoid and 3 EGR solenoids. PCM will illuminate Malfunction Indicator Light (MIL).

Monitor voltage at each terminal shown above while moving related harness connectors, including PCM harness. If failure is induced, voltage will change. This may assist in isolating an intermittent condition. Check for bent pins at PCM and PCM connector terminals. If code reoccurs with no apparent connector problem, replace PCM.

1. PCM is protected by an internal circuit breaker.
2. PCM replacement is not necessary after repairing QDM "B" quad-driver controlled circuit or component.

Code P1650 Schematic (3.1L) QDM "B" Circuit. Scheme 51

Code P1650 Flow Chart (3.1L) QDM "B" Circuit. Scheme 52

SUMMARY

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

3.1L (VIN M) PCM Wiring Diagram (1 Of 3). Scheme 53

3.1L (VIN M) PCM Wiring Diagram (2 Of 3). Scheme 54

3.1L (VIN M) PCM Wiring Diagram (3 Of 3). Scheme 55

See also:
• BASIC TESTING
• TESTS W/O CODES
• SYSTEM/COMPONENT TESTS - 3.1L
• RETRIEVING CODES (NON-SCAN)
• HARD OR INTERMITTENT TROUBLE CODE DETERMINATION
• CLEARING TROUBLE CODES