Engine Controls - Tests W/codes Buick LeSabre VII

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 appropriate BASIC TESTING article in this section. 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 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) may 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 store a numerical code and, in most cases, illuminate SERVICE ENGINE SOON light located on instrument panel. SERVICE ENGINE SOON light is also referred to as the Malfunction Indicator Light (MIL). Malfunctions are recorded as hard failures or as intermittent failures.

Note. Models equipped with OBD II diagnostic systems may have additional diagnostic information and procedures available; however, to fully utilize information and procedures requires the use of a Tech 1 scan tester. See tester owners manual for additional information.

HARD FAILURES

Most 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 display 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, 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 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/lesabre/vii-1992-1999/remont/testing-diagnostics/#engine-controls-basic-testing) article in this section.
2. If trouble codes were displayed, 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/lesabre/vii-1992-1999/remont/testing-diagnostics/#engine-controls-tests-wcodes__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/lesabre/vii-1992-1999/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/lesabre/vii-1992-1999/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»(/buick/lesabre/vii-1992-1999/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article in this section.
4. After necessary repairs are made, clear trouble codes, verify vehicle will enter "closed loop" operation and ensure code does not reset.

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

Note. Field service mode check can only be performed on vehicles equipped with 12-pin DLC with a wire present in test terminal "B".

DATA LINK CONNECTOR (DLC) TEST TERMINALS (16 PIN)

Scheme 8

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 (some models) 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.

TROUBLE CODE DEFINITION

TROUBLE CODE CONVERSION

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/lesabre/vii-1992-1999/remont/testing-diagnostics/#engine-controls-tests-wcodes__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.

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 conditions under which code will set.

CLEARING TROUBLE CODES

To clear trouble codes from memory, either to determine if malfunction will occur again or after making necessary repairs, disconnect power supply to PCM for at least 30 seconds or clear codes using a scan tester with code clearing capability.

PCM LOCATION

On most models, engine control module is located behind right or left side of dash, behind right or left kick panel or on left or right side of engine compartment. For more precise location, see COMPONENT LOCATIONS in SYSTEM/COMPONENT TESTS 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)

Note. 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.

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. On most models scan tester is REQUIRED to retrieve vehicle information. 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 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 chart. In addition, special jumper harnesses or testers may be required by manufacturer to facilitate diagnosis.

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 or ON-BOARD DIAGNOSTIC SYSTEM CHECK located in BASIC TESTING article in this section. If vehicle does not pass diagnostic 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.

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, DO NOT use scan tester for diagnosis. Contact tester manufacturer for additional information.

SCAN DATA

Note. Information contained in SCAN DATA 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, more often on most models. 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.

SCAN DATA

ECM/PCM CODE CHARTS

Note. In following diagnostic tests, schematics and illustrations

Circuit Description

Mass Airflow (MAF) sensor measures flow of air which passes through it in a given time. PCM uses this information to monitor operating condition of 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.

Set Condition

Code P0101 will set when the following conditions are present.

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

Test Description

Note. Test numbers refer to numbers on diagnostic chart.

1. 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 Mass Airflow (MAF) sensor circuit, or poor connection.
3. Verifies both ignition feed voltage and a good ground circuit are available.

Code P0101 Schematic (3.8L) Mass Air Flow (MAF) Sensor Circuit. Scheme 9

Code P0101 Diagnostic Flow Chart (3.8L) Mass Air Flow (MAF) Sensor Circuit. Scheme 10

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

1. Mis-Routed Harness

Inspect MAF sensor harness to ensure it is not too close to high voltage wires, such as spark plug wires.

1. Damaged Harness

Inspect harness for damage. If harness appears okay, observe scan tester while moving related connectors and wiring harness. A change in display would indicate intermittent fault location.

1. Plugged Air Intake Filter

A wide-open throttle acceleration from a stop should cause MAF reading on scan tester to range from about 4-7 grams per second at idle to 100 or greater at time of 1-2 shift. If not, check for restriction.

Intake Air Temperature (IAT) sensor is a thermistor. PCM applies and monitors a 5-volt reference signal 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 airflow 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 about -29°F (-34°C) for 5 seconds.

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 scan tester to display about -40°C. This test determines if wiring and PCM are okay.

Code P0112 Schematic (3.8L) IAT Sensor Circuit Low Temperature Indicated. Scheme 11

Code P0112 Flow Chart (3.8L) IAT Sensor Circuit Low Temperature Indicated. Scheme 12

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

Intake Air Temperature (IAT) sensor is a thermistor. PCM applies and monitors a 5-volt reference signal 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. Conditions are met for at least for 5 seconds.

Note. Test numbers refer to numbers on diagnostic chart.

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

Code P0113 Flow Chart (3.8L) IAT Sensor Circuit High Temperature Indicated. Scheme 13

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 short to ground in IAT signal circuit, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.

1. Intermittent Test

Observe IAT on scan tester while moving related connectors and wiring harness with warm engine running. If failure is induced, IAT display will change to a reading of about 147°C. This may assist in isolating location of malfunction.

ECT sensor uses a thermistor to control signal voltage to PCM. PCM applies and monitors a 5-volt reference signal to sensor. When engine coolant is cold, sensor (thermistor) resistance is high and PCM will sense a high signal voltage. As engine coolant increases, sensor resistance becomes less and PCM voltage drops.

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if conditions necessary to set Code P0117 exist.
2. Determines if sensor signal circuit is shorted to ground.

Code P0117 Schematic (3.8L) Coolant Temperature Sensor Low Temperature Indicated. Scheme 14

Code P0117 Flow Chart (3.8L) Coolant Temperature Sensor Low Temperature Indicated. Scheme 15

Tech 1 displays engine temperature in degrees celsius (°C). After engine is started, temperature should rise steadily to about 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 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

Using scan tester, monitor engine coolant temperature while moving related connectors and wiring harness. If failure is induced, display will change. This may assist in isolating location of malfunction.

1. Shifted Sensor

See TEMPERATURE-TO-RESISTANCE VALUES table to test ECT sensor at various temperature levels to evaluate possibility of a shifted (mis-scaled) sensor which may result in driveability complaints.

1. A faulty connection, or an open in sensor circuits will cause Code P0117 to set.

TEMPERATURE-TO-RESISTANCE VALUES (1)

ECT sensor uses a thermistor to control signal voltage to PCM. PCM applies and monitors a 5-volt reference signal to sensor. When engine coolant is cold, sensor (thermistor) resistance is high and PCM will sense a high signal voltage. As engine coolant warms, 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.

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if conditions necessary to set code 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 sensor circuits are open. If circuits are okay, check connections at PCM and ECT sensor.

Code P0118 Flow Chart (3.8L) Coolant Temperature Sensor High Temperature Indicated. Scheme 16

Tech 1 displays engine temperature in degrees celsius (°C). After engine is started, temperature should rise steadily to about 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 insulation. Check the following for

1. A short to ground in coolant sensor signal circuit.
2. Intermittent Test

Using scan tester, monitor engine coolant temperature while moving related connectors and wiring harness. If failure is induced, display will change. This may assist in isolating location of malfunction.

1. Shifted Sensor

See TEMPERATURE-TO-RESISTANCE VALUES table to test ECT sensor at various temperature levels to evaluate possibility of a shifted (mis-scaled) sensor which may result in driveability complaints.

TEMPERATURE-TO-RESISTANCE VALUES (1)

Throttle Position (TP) sensor provides a voltage signal that changes relative to throttle blade angle. Signal voltage will vary from about .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 PCM control outputs.

Code P0122 will set when the following conditions are present.

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

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.

Code P0122 Flow Chart (3.8L) Throttle Position Sensor Signal Voltage Low. Scheme 17

Scan tester 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.

1. Intermittent Test

Monitor TP sensor voltage display on scan tester while moving related connectors and wiring harness. If failure is induced,display will change. This may assist in isolating location of malfunction.

1. 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 (about .20-.74 volt) to greater than 4 volts when throttle is held at WOT position.

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 about 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 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 airflow 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.

Note. Test numbers refer to numbers on diagnostic chart.

1. With closed throttle, ignition on or idling, voltage at PCM TP sensor signal circuit should be about .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.

Code P0123 Flow Chart (3.8L) Throttle Position Sensor Signal Voltage High. Scheme 18

Scan tester displays throttle position in volts. With closed throttle, ignition on, or at idle, voltage should be about .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.

1. Intermittent Test

Monitor TP sensor voltage display on scan tester while moving related connectors and wiring harness. If failure is induced, display will change. This may assist in isolating location of malfunction.

1. 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 (about .20-.74 volt) to greater than 4 volts when throttle is held at WOT position.

PCM supplies and monitors a voltage of about .45 volt between PCM sensor low reference circuit and sensor signal circuit. If read with a 10-megohm DVOM, voltage may read as low as .32 volt. Sensor varies voltage within a range of about 1.0 volt (rich) to .10 volt (lean). Sensor is like an open circuit and produces no voltage when less than about 600°F (316°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. Sensor signal voltage remains low (less than closed throttle voltage) for a predetermined amount of time.
2. System is operating in closed loop.

Action Taken

Code P0131 will cause system to operate in open loop.

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 sensor signal circuit and grounding sensor low circuit should result in a displayed voltage of .35-.55 volt. If display is still fixed less than .35 volt, fault is a short to ground in signal circuit, or faulty PCM.

Code P0131 Schematic (3.8L) Heated Oxygen Sensor Low Signal Voltage (Lean). Scheme 19

Code P0131 Flow Chart (3.8L) Heated Oxygen Sensor Low Signal Voltage (Lean). Scheme 20

Using scan tester, 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.

1. Check for intermittent ground in wire between connector and sensor.
2. Poor PCM to engine block ground.
3. MAF Sensor

System will go lean when MAF sensor output causes PCM to sense a lower than normal airflow. Disconnect MAF sensor. If lean condition no longer exists, replace MAF sensor.

1. Lean Injectors

Perform injector balance test.

1. 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.

1. 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.

1. Exhaust Leaks

If an exhaust leak above oxygen sensor is present, outside air may be allowed to be pulled into exhaust stream and flow past sensor.

1. Vacuum Or Crankcase Leak

Can cause a lean condition and/or possibly a high idle.

1. If all above components/systems are okay, heated oxygen sensor is faulty.
2. Faulty sensor heater or heater circuit

Refer to DIAGNOSTICS AIDS in Code P0134 chart.

PCM supplies and monitors a voltage of about .45 volt between PCM sensor low reference circuit and sensor signal circuit. If read with a 10-megohm DVOM, voltage may read as low as .32 volt. Sensor varies voltage within a range of about 1.0 volt (rich) to .10 volt (lean). Sensor is like an open circuit and produces no voltage when less than about 600°F (316°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. Sensor voltage on signal circuit remains greater than .75 volt for at least 2 minutes while in closed loop.
2. Throttle angle is 2-40 percent.
3. Codes P0122 or P0123 are not set.

Note. Test numbers refer to numbers on diagnostic chart.

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

Code P0132 Flow Chart (3.8L) Heated Oxygen Sensor High Signal Voltage (Rich). Scheme 21

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.

1. Rich Injectors Perform injector balance test.
2. Leaking Injectors Check for fuel contaminated oil.
3. EVAP Canister Purge

Check for fuel saturation. If full of fuel, check canister control and hoses.

1. MAF Sensor

System will go rich when MAF sensor output causes PCM to sense a higher than normal airflow. Disconnecting MAF sensor will allow PCM to set a fixed value for sensor. If rich condition no longer exists, replace MAF sensor.

1. Check for leaking fuel pressure regulator diaphragm by checking vacuum line to regulator for fuel.
2. TP Sensor

An intermittent TP sensor output will cause system to go rich due to a false indication of throttle movement.

1. False rich indication due to silicone contamination of heated oxygen sensor. This will be indicated by Code P0131 accompanied by lean driveability conditions and a powdery White deposit on sensor.
2. Heated Oxygen Sensor (HO2S)

If sensor is internally shorted, sensor voltage displayed on Tech 1 will be greater than one volt. Disconnect sensor with ignition on and engine running. If displayed voltage decreases from greater than 1.0 volt to about .45 volt, replace sensor.

1. Faulty Sensor Heater Or Heater Circuit

See DIAGNOSTICS AIDS in Code P0134 chart.

PCM supplies and monitors voltage of about .45 volt between PCM sensor low reference circuit (Tan wire) and sensor signal circuit (Purple wire). If read with a 10-megohm DVOM, voltage may read as low as .32 volt. Sensor varies voltage within a range of about one volt (rich) to .10 volt (lean). Sensor is like an open circuit and produces no voltage when less than about 600°F (316°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. Sensor signal voltage is steady at .35-.56 volt.
4. Throttle angle is greater than 3 percent.
5. All conditions are met for about 30 or more seconds.

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.

Code P0134 Flow Chart (3.8L) Heated Oxygen Sensor Open Circuit. Scheme 22

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

1. Faulty Sensor Heater Or Heater Circuit

With ignition on and engine off, sensor 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 sensor 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 sensor.

1. Intermittent Test

Using scan tester, monitor sensor signal voltage while moving related connectors and wiring harness with engine running at part throttle in closed loop. If failure is induced, sensor signal voltage reading will change from normal fluctuating voltage (greater than .6 volt and less than .30 volt) to a fixed value of about .45 volt. This may assist in isolating location of malfunction.

A closed loop air/fuel metering system is used to provide best possible combination of driveability, fuel economy and emission control. While in closed loop, PCM monitors oxygen sensor signal voltage and adjusts fuel delivery based on signal voltage. Scan tester monitors fuel trim values, and will indicate a change made to fuel delivery by long and short term fuel trim values.

Ideal fuel trim values are about 128. If oxygen sensor signal indicates a lean condition, PCM will add fuel, resulting in a fuel trim value greater than 128. If a rich condition is detected, fuel trim values will be less than 128, indicating that PCM is reducing amount of fuel delivered. PCM will set Code P0171 if an excessively lean condition is detected.

Code P0171 will set when the following conditions are present.

1. Codes P0101, P0117, P0118, P0122, P0123, P0134, P0501 and P0502 are not set.
2. Engine coolant temperature is between 176°F (80°C) and 230°F (110°C).
3. Steady throttle less than 91 percent.
4. Vehicle speed is less than 70 MPH.
5. On VIN L, engine RPM is between 1000-4000 RPM, or on VIN 1, engine RPM is 0-4000 RPM.
6. EVAP canister purge duty cycle is less than 80 percent.
7. Long term fuel trim is greater than 158.
8. Short term fuel trim is 180.
9. All conditions exist for more than 25 seconds.

Preliminary Inspection

1. Check exhaust for corrosion, loose or missing components.
2. Ensure oxygen sensor is installed properly and pigtail is not contacting hot exhaust or ignition wires.
3. Check vacuum hoses for splits, kinks and proper routing and connections.
4. Check for vacuum leaks at throttle body, intake manifold and EGR valve.
5. Check for proper operation of IAC system.
6. Check proper operation of PCV system.
7. Check throttle body inlet screen for damage and/or foreign objects.
8. Check fuel for excessive water, alcohol, or other contaminates.
9. Ensure PCM and sensor grounds are clean and tight. NOTE: To complete a trip cycle for fuel trim diagnostic, fuel trim diagnostic test must be enabled and run according to conditions required to set Code P0171. A trip is not considered complete until fuel trim diagnostics have been run by PCM.

Note. Test numbers refer to numbers on diagnostic chart.

1. Visually/physically checking components/systems which may cause a lean condition may determine cause of Code P0171.
2. MAF sensor which causes PCM to read a lower than actual airflow can cause a lean condition, and Code P0171 to set.
3. Check for faults in EVAP purge system that may cause Code P0171 to set.

Code P0171 Diagnostic Flow Chart - 1 Of 2 (3.8L) Fuel Trim Lean. Scheme 23

Code P0171 Diagnostic Flow Chart - 2 Of 2 (3.8L) Fuel Trim Lean. Scheme 24

If problem can not be isolated using diagnostic charts, monitor LT fuel trim and fuel trim cell while operating vehicle under various loads. This may isolate condition which caused Code P0171 to set.

A condition that causes Code P0300 (MISFIRE DETECTED) may also set Code P0171. An extremely lean condition which sets Code P0171 can cause a misfire at idle and Code P0300 to set. If cause of Code P0171 can not be determined and Code P0300 is also set, refer to Code P0300 chart.

A closed loop air/fuel metering system is used to provide best possible combination of driveability, fuel economy and emission control. While in closed loop, PCM monitors oxygen sensor signal voltage and adjusts fuel delivery based on signal voltage. Scan tester monitors fuel trim values, and will indicate a change made to fuel delivery by long and short term fuel trim values.

Ideal fuel trim values are about 128. If oxygen sensor signal indicates a lean condition, PCM will add fuel, resulting in a fuel trim value greater than 128. If a rich condition is detected, fuel trim values will be less than 128, indicating PCM is reducing amount of fuel delivered. PCM will set Code P0172 if an excessively rich condition is detected.

Code P0172 will set when the following conditions are present.

1. Codes P0101, P0117, P0118, P0122, P0123, P0501 and P0502 are not set.
2. Engine coolant temperature is between 176°F (80°C) and 230°F (110°C).
3. Steady throttle less than 91 percent.
4. Vehicle speed is less than 70 MPH.
5. On VIN L, engine RPM is 1000-4000 RPM, or on VIN 1, engine RPM is 0-4000 RPM.
6. EVAP canister purge duty cycle is less than 80 percent.
7. Long term fuel trim is less than 100.
8. Short term fuel trim is less than 94.
9. All conditions exist for more than 25 seconds.

1. Ensure air intake duct is not collapsed or restricted and air filter is not plugged.
2. Check for damaged or partially plugged throttle body inlet screen.
3. Check for proper operation of IAC system.
4. Check fuel pressure regulator operation, ensuring diaphragm is not ruptured.
5. Check for proper operation and mounting of throttle position sensor. NOTE: To complete a trip cycle for fuel trim diagnostic, fuel trim diagnostic test must be enabled and run according to conditions required to set Code P0172. A trip is not considered complete until fuel trim diagnostic has been run by PCM.

Note. Test numbers refer to numbers on diagnostic chart.

1. Visually/physically checking components/systems which may cause a rich condition may determine cause of Code P0172.
2. MAF sensor which causes PCM to read a higher then actual airflow can cause a rich condition, and Code P0172 to set.
3. Silicone contamination of Heated Oxygen Sensor (HO2S) can cause a false rich indication that will be sensed by PCM. PCM will then reduce amount of fuel delivered, possibly causing severe driveability symptoms.

Code P0172 Diagnostic Flow Chart - 1 Of 2 (3.8L) Fuel Trim Rich. Scheme 25

Code P0172 Diagnostic Flow Chart - 2 Of 2 (3.8L) Fuel Trim Rich. Scheme 26

If problem can not be isolated using diagnostic charts, monitor LT fuel trim and fuel trim cell while operating vehicle under various loads. This may isolate condition which caused Code P0172 to set.

PCM uses spark reference signal circuit to improve ignition timing accuracy during crank and at engine speeds up to 1200 RPM. Spark reference circuit allows use of ignition control mode at speeds less than 400 RPM, eliminating need to utilize module mode during start-up, and also allows PCM to calculate true crankshaft position in 1/6 the time that use of fuel control reference signal would permit.

During normal operation, PCM uses spark reference signal to control ignition timing until engine speed exceeds 1200 RPM, at which time fuel control reference signal circuit is used.

Code P0321 will set when the following conditions are present.

1. PCM detects 150 fuel control reference pulses (50 crank revolutions) and no spark reference pulses.
2. Engine speed is less than 1200 RPM.
3. Engine is running.

Fuel reference signal is used by PCM to control ignition timing advance when conditions for setting Code P0321 are present. This condition will cause module mode to be used for ignition timing less than 400 RPM and PCM controlled ignition timing to be degraded less than 1200 RPM.

Note. Test numbers refer to numbers on diagnostic chart.

1. Verifies short to ground is not present in spark reference circuit, or an open is not present in ignition jumper harness.
2. Ignition control module will ground spark reference signal if a window on harmonic balancer is interfacing with 18X Hall Effect switch. Starter may have to be bumped several times to obtain a voltage reading.
3. Voltage reading should be lower than that obtained with engine not running, indicating a pulsed reference signal.

Code P0321 Schematic (3.8L) Spark Reference Circuit. Scheme 27

Code P0321 Diagnostic Flow Chart (3.8L) Spark Reference Circuit. Scheme 28

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

1. Backed out connector terminals or broken down insulation.
2. If connections and harness are okay, monitor voltage on spark reference circuit using DVOM while moving related wiring harness and connectors with engine idling. This may assist in isolating any malfunctions.

Knock sensor is used to detect engine detonation and allow PCM to retard Ignition Control (IC) timing based on signal being received. 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 about 2.5 volts DC. Knock sensor produces an AC signal which rides on 2.5 volts DC voltage. Amplitude and signal frequency is dependent upon 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 respectively.

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.

Note. Test numbers refer to numbers on diagnostic chart.

1. If Code P0325 is detected, PCM will retard spark timing. If an audible knock 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.
3. Determines if knock sensor is faulty or if knock sensor portion of PROM is faulty.

Code P0325 Schematic (3.8L) Knock Sensor Error (Single Sensor). Scheme 29

Code P0325 Diagnostic Flow Chart (3.8L) Knock Sensor Error (Single Sensor). Scheme 30

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.

Knock sensor is used to detect engine detonation and allow PCM to retard Ignition Control (IC) timing based on signal being received. 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 about 2.5 volts DC. Knock sensor produces an AC signal which rides on 2.5 volts DC voltage. Amplitude and signal frequency is dependent upon 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 respectively.

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.

Note. Test numbers refer to numbers on diagnostic chart.

1. If Code P0325 is detected, PCM will retard spark timing. If an audible knock 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 both knock sensor terminals.
3. Determines if knock sensor is faulty or if knock sensor portion of PROM is faulty.
4. Check knock sensor circuit for an intermittent open or short to ground. Also check for proper PROM installation.

Code P0325 Schematic (3.8L) Knock Sensor Error (Dual Sensors). Scheme 31

Code P0325 Diagnostic Flow Chart (3.8L) Knock Sensor Error (Dual Sensors). Scheme 32

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.

During cranking, Ignition Control Module (ICM) monitors crankshaft position sensor signal. Signal is used to determine correct cylinder pair to spark first. ICM processes 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 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 fuel from priming shot.

During this waiting period, a cam pulse will have been received by PCM. PCM will now begin to operate 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 ratio of fuel control pulses to cam pulses does not equal 6 for 10 occurrences during key cycle.

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if conditions necessary to set Code P0341 exist.
2. If 5 volts are not present at PCM harness connector terminal cam signal circuit, camshaft position senor may be interfacing with magnet in camshaft sprocket. Bumping starter should correct this condition.
3. If a failure is induced in fuel control reference circuit, 5 volts on circuit should change when faulty wiring or connection is manipulated.

Code P0341 Diagnostic Flow Chart (3.8L) Cam/Crank Error. Scheme 33

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 of 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.

A poor connection or fault in fuel control circuit, crankshaft position sensor circuits, 18X portion of crankshaft position sensor, or damaged vanes on harmonic balancer interrupter rings will cause PCM to stop pulsing injectors when fault occurs, causing an intermittent stumble or stall.

During cranking, Ignition Control Module (ICM) monitors crankshaft position sensor signal. Signal is used to determine correct cylinder pair to spark first. ICM processes 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 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 fuel from priming shot.

During this waiting period, a cam pulse will have been received by PCM. PCM will now begin to operate injectors sequentially based on true camshaft position. However, if cam signal is not present at start-up, Code P0342 will set and PCM will start sequential fuel delivery in random pattern with a one in 6 chance that fuel delivery is correct.

Code P0342 will set when engine is running and cam signal is not received by PCM for last 5 seconds.

Note. Test numbers refer to numbers on diagnostic chart.

1. This step verifies integrity of sensor circuits.
2. This step verifies integrity of circuit between ICM and PCM.
3. Voltage reading will be zero if camshaft gear magnet is interfacing with camshaft position sensor.
4. If voltage reading of cam signal circuit is constantly varying and connection to PCM is good, PCM is faulty.

Code P0342 Diagnostic Flow Chart (3.8L) Cam Signal Circuit. Scheme 34

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

1. Poor Connection Or Damaged Harness

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

1. Intermittent Test

If connections and harness are okay, monitor a DVOM connected between PCM cam signal circuit terminal and ground while moving related connectors and wiring harness. If failure is induced, voltage reading will change. This may assist in isolating location of malfunction.

PCM tests exhaust gas recirculation valve by momentarily commanding valve on while monitoring engine RPM. PCM will illuminate Malfunction Indicator Light (MIL) and store Code P0401 if expected drop is not seen for a calibrated number of tests.

Monitor Condition

PCM will run EGR test when the following conditions are present.

1. Codes P0122, P0123 or P0501 are not set.
2. Brake has been applied.
3. Engine coolant temperature is greater than 185°F (85°C).
4. Throttle angle is less than one percent.
5. Vehicle speed is greater than 25 MPH.
6. Engine speed is 900-1100 RPM.

Code P0401 will set when PCM does not detect a decrease in engine speed of at least 50 RPM for 6 out of 8 tests. Once 3 tests are run during an ignition cycle, PCM will not run any further flow tests until next ignition cycle. Thus, 3 or more ignition cycles will be necessary to set Code P0401.

Note. Test numbers refer to numbers on diagnostic chart.

1. Ensures EGR valve is allowing EGR flow and PCM is capable of controlling EGR valve.
2. Ensures control circuit is not shorted to ground.
3. Ensures control circuit is not open and that PCM quad-driver for circuit is properly functioning.

Code P0401 Schematic (3.8L) (EGR) Flow Test Failure. Scheme 35

Code P0401 Diagnostic Flow Chart (3.8L) (EGR) Flow Test Failure. Scheme 36

An intermittent may be caused by a broken wire inside insulation. Check for

1. Poor Connection Or Damaged Harness

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

1. Intermittent Test

If connections and harness are okay, monitor a DVOM connected between PCM EGR control circuit terminal and ground while moving related connectors and wiring harness. If failure is induced, voltage reading will change.

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 stuck open may be due to stuck injector pintle, grounded driver circuit or possible faulty PCM. If conditions are not present, oil should be checked for possible fuel contamination.

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

Function of 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.

Set Condition P0501

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.

Set Condition P0502

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.

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.

Codes P0501/P0502 Schematic (3.8L) VSS Circuit. Scheme 37

Codes P0501/P0502 Diagnostic Flow Chart (3.8L) VSS Circuit. Scheme 38

When vehicle speed is greater than about 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.

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 scan tester.

Code P0703 Schematic (3.8L) TCC Brake Switch Input. Scheme 39

Code P0703 Diagnostic Flow Chart (3.8L) TCC Brake Switch Input. Scheme 40

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 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

Monitor scan tester 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 location of malfunction.

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 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

1. 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.

Note. Test numbers refer to numbers on diagnostic chart.

1. & 2) 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.

Code P0705 Schematic (3.8L) Transaxle Range Switch. Scheme 41

Code P0705 Diagnostic Flow Chart (3.8L) Transaxle Range Switch. Scheme 42

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 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

Monitor scan tester 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 location of malfunction.

Transaxle temperature sensor uses a thermistor to vary signal voltage to PCM according to temperature. PCM applies and monitors a 5-volt reference signal 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 68-194°F (20-90°C) transaxle temperature signal will measure about 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 about -40°F (-40°C).
3. Above conditions for over 1.6 second.

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.
3. Determines if transaxle fluid temperature sensor signal circuit is open. There should be 5 volts present at sensor connector.

Code P0712 Diagnostic Flow Chart (3.8L) Transaxle Temperature Sensor Low Temperature Indicated. Scheme 43

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 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

Monitor scan tester 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.

1. Shifted Sensor

See TEMPERATURE-TO-RESISTANCE VALUES table to test sensor at various temperature levels to evaluate possibility of a shifted sensor which may result in driveability complaints.

1. A faulty connection, or an open in sensor circuits will cause Code P0117 to set.

TEMPERATURE-TO-RESISTANCE VALUES (1)

Transaxle temperature sensor uses a thermistor to vary signal voltage to PCM according to temperature. PCM applies and monitors a 5-volt reference signal 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 68-194°F (20-90°C) transaxle temperature signal will measure about 2-4 volts.

Code P0713 will set when the following conditions are present.

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

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.

Code P0713 Diagnostic Flow Chart (3.8L) Transaxle Temperature Sensor High Temperature Indicated. Scheme 44

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 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

Monitor scan tester 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.

1. Shifted Sensor

See TEMPERATURE-TO-RESISTANCE VALUES table to test sensor at various temperature levels to evaluate possibility of a shifted (mis-scaled) sensor which may result in driveability complaints.

TEMPERATURE-TO-RESISTANCE VALUES (1)

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

TCC is applied when 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. All conditions exist for over 10 seconds.

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.

Code P0740 Diagnostic Flow Chart (3.8L) Torque Converter Clutch. Scheme 45

Scan tester 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 tester indicates TCC has been turned on. If diagnosis indicates all electrical circuits and components are okay, check for hydraulic and mechanical problems.

The 4T60E is an electronically shifted transaxle. Within 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 about 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-to-vehicle speed does not indicate 1st gear. - Conditions exist 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-to-vehicle speed does not indicate 4th gear (LV8 less than 80). - Conditions exist for 2 seconds.

Code P0755 Diagnostic Flow Chart "B" (3.8L) Transmission Shift Solenoid. Scheme 46

PCM controls and monitors injector driver circuits. If any injector feed or control circuit malfunctions, code will set.

Note. Test numbers refer to numbers on diagnostic chart.

1. Ensures no faults exist in injector control and ignition feed wiring.
2. Checks for open or grounded injector feed circuit.
3. Checks for grounded injector drive circuit.
4. Checks for an open injector drive circuit.

Code P1200 Diagnostic Flow Chart (3.8L) Injector Circuit Fault. Scheme 47

An intermittent may be caused by rubbed through wire insulation. Check for

1. Boost control driver circuit shorted to ground.

Intermittent Test

Disconnect PCM Blue connector and install a DVOM to monitor voltage between PCM harness boost control driver circuit terminal and ground. With ignition on, observe voltage while moving related connectors and wiring harness. If failure is induced, voltage reading will change.

Under most conditions, PCM commands boost control solenoid to operate at a 100 percent duty cycle (on) to allow full intake boost pressure upon demand. However, if reverse gear is selected, PCM detects rapid deceleration or engine load is extremely high, reduced boost is desired. Under these conditions, PCM commands boost control solenoid to operate at a zero percent duty cycle (off), which opens by-pass valve to reduce boost pressure by recirculating it back through supercharger inlet.

Code P1257 will set when the following conditions are present.

1. Intake air temperature is greater than 0°F (-18°C).
2. Boost duty cycle less than 100 percent.
3. Engine torque exceeds a calibrated maximum torque value. This value varies depending on commanded gear and engine RPM.
4. Conditions exist for at least 6 seconds.

Note. Test numbers refer to numbers on diagnostic chart.

1. Circuit shorted to ground will keep by-pass valve closed when PCM is commanding it open, possibly causing an overboost condition during high engine load situations.
2. No inlet vacuum to by-pass valve actuator may cause by-pass valve to remain closed during deceleration. This condition may be perceived as a sail-on, possibly accompanied by a rough idle.

Code P1257 Schematic (3.8L (VIN 1)) Boost Control Problem. Scheme 48

Code P1257 Diagnostic Flow Chart (3.8L (VIN 1)) Boost Control Problem. Scheme 49

An intermittent may be caused by rubbed through wire insulation. Check for

1. Boost control driver circuit shorted to ground.

Disconnect PCM Blue connector and install a DVOM to monitor voltage between PCM harness boost control driver circuit terminal and ground. With ignition on, observe voltage while moving related connectors and wiring harness. If failure is induced, voltage reading will change.

When engine is cranking, Ignition Control Module (ICM) sends a spark reference and a fuel control signal to PCM. At start of crank, ICM controls ignition timing (module mode). PCM sends a 5-volt signal on by-pass circuit to switch timing to PCM control when second fuel control pulse is recognized by PCM. Code P1350 will set at start-up if an open is present in ignition control circuit. Code P1361 will set if an open in Ignition Control (IC) circuit, or an open or grounded by-pass circuit is present during time when engine is started. Engine may be started but will run on module mode timing.

Code P1350 will set when the following condition is present.

1. IC circuit opens during engine run mode.

Code P1361 will set when following condition is present.

1. IC circuit grounded during start-up.

or

1. PCM not commanding IC mode (open or grounded by-pass circuit) when engine is started.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks if PCM recognizes a problem. If Codes P1350/P1361 are not set, problem is intermittent and could be caused by a loose connection.
2. With PCM disconnected, ohmmeter reading should be less than 2000 ohms, which is normal resistance of IC circuit through ICM. A higher resistance indicates a fault in IC circuit, a poor ignition module connection, or a faulty ICM.
3. If test light lights when connected between 12 volts and PCM by-pass circuit terminal, then either by-pass circuit is shorted to ground, or ICM is faulty.
4. Checks if ICM switches when by-pass circuit is energized by 12 volts through test light. If ICM switches, ohmmeter reading should shift to greater than 6000 ohms.
5. Disconnecting ICM should make ohmmeter read as if an open circuit was being monitored (infinite reading). Otherwise, IC circuit is shorted to ground.

Codes P1350/P1361 Schematic (3.8L) IC Circuit. Scheme 50

Codes P1350/P1361 Diagnostic Flow Chart (3.8L) IC Circuit. Scheme 51

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 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

Monitor a DVOM connected between affected terminal and ground while moving related connectors and wiring harness. If failure is induced, voltage reading will change.

PCM constantly monitors linear EGR valve pintle position sensor to ensure valve is responding properly to commands from PCM.

Code P1406 will set when the following conditions are present.

1. EGR pintle position signal indicates a voltage out of normal range of pintle position sensor, or a signal that is 10 percent greater or less than PCM commanded position.
2. Either condition for up to 20 seconds.

Note. Test numbers refer to numbers on diagnostic flow chart (1 Of 2). see scheme 60: Code P1406 Schematic (3.8L) EGR Valve Pintle Position see scheme 61: Code P1406 Diagnostic Flow Chart - 1 Of 2 (3.8L) EGR Valve Pintle Position

1. Checks for an EGR valve sticking partially open or an incorrect pintle position sensor feedback signal.
2. Ensures PCM is capable of controlling EGR pintle position and is reading pintle position feedback signal properly.
3. Checks EGR valve driver in circuit and PCM.

Note. Test numbers refer to numbers on diagnostic chart (2 Of 2).

Code P1406 Diagnostic Flow Chart - 2 Of 2 (3.8L) EGR Valve Pintle Position. Scheme 52

1. Checks will diagnose an incorrect EGR pintle position sensor input signal. This test verifies a 5-volt reference at EGR valve.
2. Ensures position signal circuit is not shorted to ground.
3. Checks position signal circuit for an open.

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 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

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.

Code will set if switch indicates and open for 3 consecutive start-up cycles or if input circuit is grounded, Code P0703 is not set, transaxle is in 3rd or 4th gear, TCC is locked and conditions exist for one second.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks for closed switch in Park.
2. Checks for on open switch in Drive.
3. Ensure scan tester does not indicate P/N "actual" as yes even when wiggling shifter. This tests for an intermittent or misadjusted switch.

Code P1520 Schematic (3.8L) Park/Neutral Switch. Scheme 53

Code P1520 Diagnostic Flow Chart (3.8L) Park/Neutral Switch. Scheme 54

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

Perform intermittent check by monitoring circuit and code status while wiggling related wiring and connectors. If failure is induced, monitored circuit status will change rapidly and/or related code will set.

A/C head pressure switch opens at 200-220 psi. When head pressure switch interrupts ground at PCM, left fan should run at high speed.

Code P1530 will set when the following conditions are present.

1. Fan request circuit is grounded during first 6 seconds of engine run time.
2. Engine coolant temperature is less than 88°F (31°C).
3. Ambient air temperature is less than 82°F (28°C).
4. RPM is less than 1800.
5. Codes P0101, P0112, P0113, P0117 or P0118 are not set.
6. All conditions must be met at same time.

Code P1530 Schematic (3.8L) A/C Head Pressure Switch. Scheme 55

Code P1530 Diagnostic Flow Chart (3.8L) A/C Head Pressure Switch. Scheme 56

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

PCM controlled cruise control system is designed to be self-monitored to ensure desired cruise servo position and actual cruise servo position are equal to one another.

PCM will set Code P1558 when actual servo position is too low when maximum servo is commanded.

Code P1558 will set when the following conditions are present.

1. Throttle angle less than 50 percent.
2. Desired servo position is 90 percent.
3. Actual servo position is less than 2 percent.
4. Above conditions for 3 seconds.

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks servo position sensor. If signal is not being received at PCM, use Code P1565 to diagnose problem.
2. Verifies vacuum portion of cruise system is operational.
3. Checks for faulty brake switch.

Code P1558 Schematic (3.8L) Cruise System Problem SPS Indicated Low. Scheme 57

Code P1558 Diagnostic Flow Chart (3.8L) Cruise System Problem SPS Indicated Low. Scheme 58

Code P1558 may set if cruise control throttle cable binds or intermittently sticks. Outside interference such as a CB antenna lead near PCM wiring harness may induce a false SPS signal and set Code P1558.

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

Cruise switch within turn signal lever receives ignition voltage from a 15-amp fuse to turn signal lever cruise switches. Cruise ON/OFF, SET/COAST and RESUME/ACCEL switches are inputs to cruise portion of PCM.

Cruise servo vent and vacuum solenoids output are controlled by high side drivers in PCM. When ignition is on, PCM looks at these output lines and will set codes if an incorrect status is seen on any line.

Vent solenoid is a normally-open (de-energized) solenoid valve that allows vacuum in cruise servo to be depleted. When solenoid is on (energized), cruise servo holds vacuum allowing servo to remain retracted and hold throttle open.

Code P1561 will set when the following conditions are present.

1. Vent driver circuit is shorted to voltage when vent solenoid is commanded off.
2. Vent driver circuit is open.
3. Vent driver circuit is shorted to ground when vent solenoid is commanded on.
4. One of above conditions are met for more than half of a second.

Code P1561 Diagnostic Flow Chart (3.8L) Cruise Vent Solenoid. Scheme 59

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

Cruise switch within turn signal lever receives ignition voltage from a 15-amp fuse to turn signal lever cruise switches. Cruise ON/OFF, SET/COAST and RESUME/ACCEL switches are inputs to cruise portion of PCM.

Cruise servo vent and vacuum solenoids output are controlled by high side drivers in PCM. When ignition is on, PCM looks at these output lines and will set codes if an incorrect status is seen on any line.

Vacuum solenoid is a normally closed solenoid valve that blocks flow of vacuum to cruise servo. When solenoid is on (energized), solenoid valve opens allowing vacuum to be drawn into servo.

Code P1562 will set when the following conditions are present.

1. Solenoid driver circuit is shorted to voltage when vacuum solenoid is commanded off.
2. Solenoid driver circuit is open.
3. Solenoid driver circuit is shorted to ground when vacuum solenoid is commanded on.
4. One of above conditions are met for more than half of a second.

Code P1562 Diagnostic Flow Chart (3.8L) Cruise Vacuum Solenoid. Scheme 60

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

PCM applies and monitors 5 volts to cruise control servo position sensor through PCM servo position sensor terminal and receives a returned frequency from servo terminal "B" on same circuit. Depending on actual servo position, AC frequency will vary indicating to PCM position of servo blade. PCM uses this information to control servo position when cruise is engaged.

Code P1565 will set when the following conditions are present.

1. Servo position signal circuit is open, grounded or shorted to voltage.

or

1. Ground circuit (low) is open.

Code P1565 Diagnostic Flow Chart (3.8L) Cruise Servo Position. Scheme 61

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

Power is supplied to cruise control switches and cruise brake switch as well as other circuits by ignition switch. Circuit is protected by a 15-amp fuse.

Code P1567 will set when the following conditions are present.

1. ON/OFF switch is open between cruise engage switch and PCM.
2. SET/COAST switch is indicated closed for more than 7 1/2 minutes (switch problem).
3. RESUME/ACCEL switch is indicated closed for more than 7 1/2 minutes (switch problem).
4. Cruise brake signal is open to PCM (no change in status of cruise brake switch) when vehicle makes 5 stops from 35 MPH (for more than 10 seconds) down to zero MPH.
5. Any circuit is shorted to voltage.
6. One of the listed conditions are met.

Code P1567 Schematic (3.8L) Cruise Switches Circuit. Scheme 62

Code P1567 Diagnostic Flow Chart (3.8L) Cruise Switches Circuit. Scheme 63

Note. A short to ground in cruise ON/OFF circuit, SET/COAST, cruise/brake or RESUME/ACCELL will cause a failure of cruise engagement switch. It will not blow 15-amp fuse.

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

PCM controlled cruise control system is designed to be self monitored to ensure desired cruise servo position and actual cruise servo position are equal to one another. When Code P1568 is set, vehicle may operate in power management mode and Code P1599 will set. While in power management, PCM will shut off fuel to 3 cylinders to avoid over-revving engine in case throttle is being held open by a sticking cruise control throttle cable, brake vacuum release valve, or cruise control servo. Power management may be perceived as a severe engine miss or lack of power.

Code P1568 will set when the following conditions are present.

1. Actual servo position is greater than 15 percent above desired servo position of zero percent for one second.

Code P1568 Diagnostic Flow Chart (3.8L) Cruise System Problem (SPS Indicated High). Scheme 64

Most solenoids leak a small amount of vacuum when closed; however, they should not leak enough to allow servo to reach WOT in 15 seconds with vent closed. When vacuum solenoid is forced on, vacuum will vent to atmosphere unless vent valve is stuck closed.

Code P1568 may set if cruise control throttle cable binds or intermittently sticks. Code P1568 can also be set by manually compressing cruise servo to raise engine speed. Outside interference such as a CB antenna lead near PCM wiring harness may induce a false SPS signal and set Code P1568.

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

Traction control system uses anti-lock brake system in conjunction with PCM fuel and ignition controls to limit drive wheel slippage during acceleration. PCM controlled portion of traction control system reduces engine torque by any or all of following methods.

1. Retarding spark advance.
2. Altering air/fuel ratio.
3. Altering boost duty cycle (VIN 1 only).
4. Shutting off up to 3 injectors.

To determine amount of torque reduction required, PCM monitors desired torque PWM signal circuit from Electronic Brake and Traction Control Module (EBTCM). PCM also provides a delivered torque PWM signal, informing EBTCM how much torque is being produced by engine. Code P1571 will set when the following condition is present.

1. If desired torque signal PWM duty cycle is less than 5 percent or greater than 95 percent. Code P1571 will set indicating a problem with desired torque input on circuit.

When Code P1571 is set, PCM will command EBTCM via serial data circuit to set ABS/TCS DTC 75, turn off traction control, and illuminate TRACTION OFF indicator. P1571 does not illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks circuit for an open or short to ground.
2. Ensures EBTCM is proving a proper PWM signal to PCM.

Code P1571 Schematic (3.8L) Traction Control Desired Torque Out Of Range. Scheme 65

Code P1571 Diagnostic Flow Chart (3.8L) Traction Control Desired Torque Out Of Range. Scheme 66

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 an open or short to ground in desired torque circuit, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection and damaged harness.

1. Intermittent Test

Using a DVOM observe voltage between PCM desired torque terminal and ground while moving related connectors and wiring harness with warm engine running. If failure is induced, voltage reading will change. This may assist in isolating location of malfunction.

PCM uses serial data line to communicate with various other components and systems within vehicle. If PCM does not receive data from Electronic Brake and Traction Control Module (EBTCM), PCM will store Code P1573 indicating loss of communication with ABS/TCS system.

Code P1573 will set when the following conditions are present.

1. Code P1630 is not set.
2. PCM has detected communication error for .5 second.

When Code P1573 is set, PCM will not be able to communicate with EBTCM. This will cause EBTCM to set ABS DTC 76, disable traction control, and illuminate TRACTION OFF indicator. P1573 does not illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks if EBTCM is able to transmit data and ensures serial data circuit to EBTCM is not open.

Code P1573 Diagnostic Flow Chart (3.8L) Traction Control Fault Loss Of ABS/TCS Serial Data. Scheme 67

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 wiring harness for an open or short to ground in serial data circuit, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection and damaged harness.

1. Intermittent Test

Observe ABS data on Tech 1 while moving related connectors and wiring harness. If failure is induced, Tech 1 data will stop updating. This may assist in isolating location of malfunction.

PCM controlled cruise control system is designed to be self monitored to ensure desired cruise servo position and actual cruise servo position are equal to one another. If actual servo position is too high, PCM will set Code P1568, and vehicle will operate in power management mode. While in power management, PCM will shut off fuel to 3 cylinders to avoid over-revving engine in case throttle is being held open by a sticking cruise control throttle cable, brake vacuum release valve, or cruise control servo. Code P1599 is an information code included to alert service that vehicle has operated in power management mode.

Code P1599 will set when vehicle has operated in power management mode.

Most solenoids leak a small amount of vacuum when closed; however, they should not leak enough to allow servo to reach WOT in 15 seconds with vent closed. When vacuum solenoid is forced on, vacuum will vent to atmosphere unless vent valve is stuck closed.

A cruise control throttle cable which binds or intermittently sticks may cause vehicle to operate in power management and Code P1599 to set. Code P1599 can also be set by manually compressing cruise servo to raise engine speed.

Outside interference such as a CB antenna lead near PCM wiring harness may induce a false SPS signal and set Code P1599.

To determine engine oil life remaining, PCM monitors engine coolant temperature, number of crankshaft revolutions, vehicle speed, engine speed, and calculated oil temperature. When PCM determines engine oil is near end of its useful life, it will command instrument cluster via serial data circuit to illuminate CHANGE OIL SOON indicator or CHANGE OIL SOON/NOW message after start-up. PCM will command CHANGE OIL SOON indicator or CHANGE OIL SOON/NOW message on after each start-up until engine oil life monitor is reset by grounding oil life monitor reset input circuit through oil life monitor reset switch for more than 5 seconds.

Code P1619 will set when the following condition is present.

1. Oil life monitor reset input circuit is grounded for more than 60 seconds.

P1619 does not illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks circuit for a short to ground.
2. Checks for a faulty PCM or an intermittent condition.

Code P1619 Schematic (3.8L) Engine Oil Life Monitor Reset Circuit. Scheme 68

Code P1619 Diagnostic Flow Chart (3.8L) Engine Oil Life Monitor Reset Circuit. Scheme 69

DTC P1623: PROM ERROR

Ensure PROM is correctly inserted in PCM 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.

When ignition is on, theft deterrent module reads key resistor pellet. If proper resistance is recognized by theft deterrent module, it sends a PWM fuel enable signal to PCM. PCM looks for this signal during crank and allows fuel delivery by enabling injectors when signal is recognized.

Set Condition Code P1626

Code P1626 will set when the following condition is present.

1. Fuel enable signal is lost after engine has started.

Set Condition Code P1629

Code P1629 will set when the following condition is present.

1. Fuel enable signal is not present during crank.

If fuel enable signal is not seen during crank, injectors will be disabled and PCM will store Code P1629, indicating a problem with theft deterrent system or fuel enable input circuit. Code P1629 will result in a cranks but will not run condition. P1629 does not illuminate Malfunction Indicator Light (MIL).

If fuel enable signal is lost while engine is running, PCM will store Code P1626 and vehicle will run normally. As long as Code P1626 is stored, PCM will ignore any absence of fuel enable signal and vehicle will restart and run as long as problem is isolated to fuel enable circuit only. P1626 does not illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. If vehicle does not crank with Code P1626 or P1629 stored, problem affects entire theft deterrent system and is not isolated to fuel enable circuit.
2. PCM supplies 5 volts to fuel enable input circuit which theft deterrent module pulses to ground when correct key resistance is recognized. This test ensures PCM is supplying 5 volts and circuit is not open or shorted to ground.
3. Checks signal from theft deterrent module. DC frequency on circuit should measure approximately 50 hertz.
4. Checks for a faulty PCM or intermittent condition by clearing Code P1626 or P1629. Since PCM ignores absence of a fuel enable signal only when Code P1626 or P1629 is stored, vehicle should not start if problem is present and Code P1626 or P1629 has been cleared.

Codes P1626/1629 Schematic (3.8L) Pass-Key II Fuel Enable Circuit. Scheme 70

Codes P1626/1629 Diagnostic Flow Chart (3.8L) Pass-Key II Fuel Enable Circuit. Scheme 71

An intermittent Code P1626 or P1629 and/or a possible no-start may be caused by the following.

1. Loss Of Power Or Ground To Theft Deterrent Module

A loose ground or poor ignition or battery condition could cause an intermittent loss of PASS-Key II fuel enable signal and Codes P1626 and P1629 to be set.

1. Dirty, Damaged, Or Loose Connections Or Damaged Harness -Check for any damage to harness which could cause an intermittent open or short to ground, backed out terminals at PCM and theft deterrent module connectors, broken locks, improperly formed or damaged terminals.

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.

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 reading is less than 9 volts or greater than 17.3 volts, repair generator.

Code P1630 Schematic (3.8L) System Voltage High/Low. Scheme 72

Code P1630 Diagnostic Flow Chart (3.8L) System Voltage High/Low. Scheme 73

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.

1. Intermittent Test

Using scan tester, monitor system volts display while moving related connectors and wiring harness. If failure is induced, display will abruptly change. This may assist in isolating location of 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.

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 No. 1 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 No. 1.
3. Brake not applied.
4. All conditions met for 5 seconds.

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.
2. If QDM No. 1 symptoms are present, checks on Code P1640 (2 Of 2) chart should isolate cause of fault.
3. This test will determine which circuit is out of specification.
4. Determines if problem is circuit or component.
5. As factory installed PCM is protected with an internal circuit breaker, it is highly unlikely that PCM needs to be replaced.

Code P1640 Schematic (3.8L) QDM No. 1 Circuit. Scheme 74

Code P1640 Diagnostic Flow Chart (3.8L) QDM No. 1 Circuit. Scheme 75

Monitor voltage at each QDM terminal 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 used to control several components as shown in wiring schematic. PCM controls these devices 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 No. 2 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 No. 2.
3. Above conditions met for 5 seconds.

Code P1650 will not 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 P1650 also.
2. This test will determine which circuit is out of specification.
3. Determines if problem is circuit or component.
4. As factory installed PCM is protected with an internal circuit breaker, it is highly unlikely that PCM needs to be replaced.

Code P1650 Schematic (3.8L) QDM No. 2. Scheme 76

Code P1650 Diagnostic Flow Chart (3.8L) QDM No. 2. Scheme 77

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 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 No. 4 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 P1670 will set.

Code P1670 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 No. 4.
3. Conditions are met for 5 seconds.

Note. Test numbers refer to numbers on diagnostic chart.

1. If QDM No. 4 related symptoms are present, checks on Code P1670 (2 OF 2) chart should isolate cause of fault.
2. Determines which circuit is out of specification.
3. Determines if problem is circuit or component.
4. As factory installed PCM is protected with an internal circuit breaker, it is highly unlikely that PCM needs to be replaced.

Code P1670 Schematic (3.8L) QDM No. 4. Scheme 78

Code P1670 Diagnostic Flow Chart (3.8L) QDM No. 4. Scheme 79

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.

Code will set if incorrect voltage level is detected on TCC PWM circuit for over 5 seconds.

Note. Test numbers refer to numbers on diagnostic chart.

1. Ensures PCM is capable of controlling solenoid.
2. Checks TCC PWM driver circuit for short to ground.

Code 1860 Schematic (3.8L) TCC PWM Solenoid. Scheme 80

Code 1860 Diagnostic Flow Chart (3.8L) TCC PWM Solenoid. Scheme 81

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

Perform intermittent check by monitoring circuit and code status while wiggling related wiring and connectors. If failure is induced, monitored circuit status will change rapidly and/or related code will set.

SUMMARY

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

3.8L (VIN K, L & 1) PCM Wiring Diagram (1 Of 3). Scheme 82

3.8L (VIN K, L & 1) PCM Wiring Diagram (2 Of 3). Scheme 83

3.8L (VIN K, L & 1) PCM Wiring Diagram (3 Of 3). Scheme 84

See also:
• BASIC TESTING
• TESTS W/O CODES
• SYSTEM/COMPONENT TESTS
• HARD OR INTERMITTENT TROUBLE CODE DETERMINATION
• SCAN TESTER USAGE
• SCAN DATA
• DTC P0101
• DTC P1623
• CLEARING TROUBLE CODES