Engine Controls - Tests W/codes - 3.4l Chevrolet Lumina I

INTRODUCTION

Most engine control problems are the result of mechanical breakdowns, poor electrical connections or damaged vacuum hoses. Before considering the computer system as a possible cause of problems, perform checks and inspections covered in the 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 the 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»(/chevrolet/lumina/i-1989-2001/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»(/chevrolet/lumina/i-1989-2001/remont/testing-diagnostics/#engine-controls-tests-wcodes-34l__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»(/chevrolet/lumina/i-1989-2001/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»(/chevrolet/lumina/i-1989-2001/remont/testing-diagnostics/#engine-controls-tests-wo-codes) article in this section. Doing so will help identify proper system or component to check in «SYSTEM/COMPONENT TESTS - 3.4L»(/chevrolet/lumina/i-1989-2001/remont/testing-diagnostics/#engine-controls-systemcomponent-tests-34l) 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". See DATA LINK CONNECTOR (DLC) TEST TERMINALS .

DATA LINK CONNECTOR (DLC) TEST TERMINALS

Scheme 62

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.

If scan tester is not available, reading flashes of SERVICE ENGINE SOON light is possible by grounding diagnostic test terminal "B" (if a wire is present) of DLC with ignition on and engine off. (Scheme 62) For example, "FLASH, FLASH, pause, FLASH, longer pause" identifies Code 21. First series of flashes is first digit of trouble code. Second series of flashes is second digit of trouble code. Trouble codes are displayed starting with lowest numbered code. Each code is displayed 3 times. Codes will continue to repeat as long as DLC test terminal is grounded.

TROUBLE CODE DEFINITIONS

TROUBLE CODE DEFIITIONS

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»(/chevrolet/lumina/i-1989-2001/remont/testing-diagnostics/#engine-controls-tests-wcodes-34l__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 - 3.4L article in this section.

Diagnostic Aids

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

Field Service Mode Check (If Available)

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

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

CODE 14, COOLANT TEMP SENS SGNL VLTGE LOW (HI TEMP INDICATED)

Code will set if PCM sees an extremely high temperature signal (low voltage). Most likely causes of code are: sensor signal circuit shorted to ground, faulty coolant temperature sensor or faulty PCM.

Note. This chart assumes engine cooling system is functioning properly (not overheating). Test numbers refer to numbers on diagnostic chart.

1. This checks if conditions for code still exist.
2. This tests for grounded sensor signal line between control module and coolant sensor.

After engine is started, temperature should rise steadily to about 90°C and then stabilize when thermostat opens. At normal operating temperature, signal voltage at control module terminal should be 1.5-2.0 volts. Check sensor for shifted calibration by using sensor TEMPERATURE-TO-RESISTANCE VALUES table. When code is set, control module will turn on electric cooling fan(s) if equipped.

CODE 14 PCM TERMINAL & CIRCUIT WIRING IDENTIFICATION

TEMPERATURE-TO-RESISTANCE VALUES (1)

1. For shared sensor ground tie-offs, see appropriate wiring diagram in WIRING DIAGRAMS section.

Code 14 Schematic (3.4L) Coolant Temperature Sensor Signal Voltage Low (High Temp. Indicated). Scheme 63

Code 14 Diagnostic Flow Chart (3.4L) Coolant Temperature Sensor Signal Voltage Low (High Temp. Indicated). Scheme 64

CODE 51, FAULTY PROM/MEM-CAL

Ensure all pins are fully inserted in socket. If pins are okay, replace PROM/MEM-CAL, clear memory and recheck. If code reappears, replace control module.

CODE 52, FAULTY CAL-PAK

Ensure all pins are fully inserted in socket. If pins are okay, replace CAL-PAK, clear memory and recheck. If Code 51 reappears, replace control module.

CODE 55, PCM ERROR

Ensure PCM grounds are okay. Ensure correct EPROM is being used and that it is properly installed. If okay, replace PCM. Clear codes, confirm closed loop operation and check operation of Malfunction Indicator Light (MIL).

CODE P0101, MASS AIR FLOW (MAF) SENSOR CIRCUIT

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.

Code P0101 will set when the following conditions are present.

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

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.

Code P0101 Schematic (3.4L) Mass Air Flow (MAF) Sensor Circuit. Scheme 65

Code P0101 Flow Chart (3.4L) Mass Air Flow (MAF) Sensor Circuit. Scheme 66

CODE P0112, IAT SENSOR CIRCUIT LOW TEMPERATURE INDICATED

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.

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.

Code P0112 Schematic (3.4L) IAT Sensor Circuit Low Temperature Indicated. Scheme 67

Code P0112 Flow Chart (3.4L) IAT Sensor Circuit Low Temperature Indicated. Scheme 68

CODE P0113, IAT SENSOR CIRCUIT HIGH TEMPERATURE INDICATED

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.

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.

Code P0113 Flow Chart (3.4L) IAT Sensor Circuit High Temperature Indicated. Scheme 69

CODE P0117, COOLANT TEMP. SENSOR LOW TEMPERATURE INDICATED

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.

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)

Code P0117 Flow Chart (3.4L) Coolant Temperature Sensor Low Temperature Indicated. Scheme 70

CODE P0118, COOLANT TEMP. SENSOR HIGH TEMPERATURE INDICATED

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.

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)

Code P0118 Flow Chart (3.4L) Coolant Temperature Sensor High Temperature Indicated. Scheme 71

CODE P0122, THROTTLE POSITION SENSOR SIGNAL VOLTAGE LOW

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.

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.

Code P0122 Flow Chart (3.4L) Throttle Position Sensor Signal Voltage Low. Scheme 72

CODE P0123, THROTTLE POSITION SENSOR SIGNAL VOLTAGE HIGH

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.

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.

Code P0123 Flow Chart (3.4L) Throttle Position Sensor Signal Voltage High. Scheme 73

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

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.

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.

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.

Code P0131 Schematic (3.4L) Heated Oxygen Sensor Low Signal Voltage (Lean). Scheme 74

Code P0131 Flow Chart (3.4L) Heated Oxygen Sensor Low Signal Voltage (Lean). Scheme 75

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

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.

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.

Code P0132 Flow Chart (3.4L) Heated Oxygen Sensor High Signal Voltage (Rich). Scheme 76

CODE P0134, HEATED OXYGEN SENSOR OPEN CIRCUIT

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.

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 hrottle 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.

Code P0134 Flow Chart (3.4L) Heated Oxygen Sensor Open Circuit. Scheme 77

CODE P0321, IGNITION CONTROL 24X SIGNAL CIRCUIT ERROR

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

Code P0321 will set when the following conditions are present.

1. 150 or more 3X reference pulses seen without a 24X signal pulse received.
2. Engine speed is less than 1200 RPM.
3. Engine is running. NOTE: Test numbers refer to numbers on diagnostic chart.

1. Determines if signal voltage is present up to PCM.
2. Determines if 12 volts at sensor input.
3. By applying battery voltage to 24X crankshaft sensor circuit, harness and sensor integrity can be determined.
4. Checks ground path continuity.

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

Code P0321 Schematic (3.4L) Ignition Control 24X Signal Circuit Error. Scheme 78

Code P0321 Diagnostic Flow Chart (3.4L) Ignition Control 24X Signal Circuit Error. Scheme 79

CODE P0325, KNOCK SENSOR ERROR (SINGLE SENSOR)

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.

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

Code P0325 Schematic (3.4L) Knock Sensor Error (Single Sensor). Scheme 80

Code P0325 Diagnostic Flow Chart (3.4L) Knock Sensor Error (Single Sensor). Scheme 81

CODE P0341, CAM SIGNAL ERROR

During cranking, Ignition Control Module (ICM) monitors 3X crankshaft position sensor signal. The 3X signal is used to determine correct cylinder pair to spark first. ICM processes 3X signal then sends a fuel control reference pulse to PCM. When PCM receives this pulse, all 6 injectors will be commanded to open for one priming shot of fuel in all cylinders. After 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 the following conditions are present.

1. Cam signal is intermittent.
2. Ratio of fuel control pulses to cam pulses does not equal 6.
3. Above condition for 10 occurrences during key cycle. NOTE: Test numbers refer to numbers on diagnostic chart.

1. If a failure is induced in fuel control reference circuit, voltage on circuit should change when faulty wiring or connection is manipulated.
2. Checks for an intermittent problem with fuel control reference signals to PCM.

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

Code P0341 Diagnostic Flow Chart (3.4L) Cam Signal Error. Scheme 82

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

During cranking, Ignition Control Module (ICM) monitors 3X crankshaft position sensor signal. The 3X signal is used to determine correct cylinder pair to spark first. ICM processes 3X signal then sends a fuel control reference pulse to PCM. When PCM receives this pulse, all 6 injectors will be commanded to open for one priming shot of fuel in all cylinders. After 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 P0342 will set when the following conditions are present.

1. Cam reference pulses are not detected by PCM for 5 seconds while engine is running. NOTE: Test numbers refer to numbers on diagnostic chart.

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

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

Code P0342 Diagnostic Flow Chart (3.4L) Camshaft Position Sensor Circuit (Loss Of Cam Pulses). Scheme 83

CODES P0501/P0502, VSS CIRCUIT

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.

Code P0501 will set when the following conditions are present.

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

Code P0502 will set when the following conditions are present.

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

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

When vehicle 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.

Codes P0501/P0502 Schematic (3.4L) VSS Circuit. Scheme 84

Codes P0501/P0502 Diagnostic Flow Chart (3.4L) VSS Circuit. Scheme 85

CODE P0703, TCC BRAKE SWITCH INPUT

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

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

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.

Code P0703 Schematic (3.4L) TCC Brake Switch Input. Scheme 86

Code P0703 Diagnostic Flow Chart (3.4L) TCC Brake Switch Input. Scheme 87

CODE P0705, TRANSAXLE RANGE SWITCH

Transmission range switch is part of Transmission Mounted Neutral Start Switch (TMNSS) mounted on transaxle assembly. Transmission range switch is a multi-signal switch that sends information, relative to gear selector position, to PCM. PRNDL input consists of 4 discrete circuits to pull 4 PCM voltages low in various combinations to indicate each gear range. Voltage level of each of 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. This step checks for proper operation of transmission range switch.
2. This test checks for an open or grounded circuit. When Code P0705 is present, PCM assumes drive-4 position until a correct combination is received by PCM. Some gear select positions may not be possible until fault is repaired.

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

Code P0705 Schematic (3.4L) Transaxle Range Switch. Scheme 88

Code P0705 Diagnostic Flow Chart (3.4L) Transaxle Range Switch. Scheme 89

CODE P0712, TRANSAXLE TEMP SENSOR LOW TEMPERATURE INDICATED

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.

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)

Code P0712 Diagnostic Flow Chart (3.4L) Transaxle Temperature Sensor Low Temperature Indicated. Scheme 90

CODE P0713, TRANSAXLE TEMP SENSOR HIGH TEMPERATURE INDICATED

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.

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)

Code P0713 Diagnostic Flow Chart (3.4L) Transaxle Temperature Sensor High Temperature Indicated. Scheme 91

CODE P0740, TORQUE CONVERTER CLUTCH

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.

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.

Code P0740 Diagnostic Flow Chart (3.4L) Torque Converter Clutch. Scheme 92

CODE P0755, TRANS. SHIFT SOLENOID "B"

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" (3.4L) Transmission Shift Solenoid. Scheme 93

CODES P1350/P1361, IC CIRCUIT

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.

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.

Codes P1350/P1361 Schematic (3.4L) IC Circuit. Scheme 94

Codes P1350/P1361 Diagnostic Flow Chart (3.4L) IC Circuit. Scheme 95

CODES P1403/P1404/P1405, EGR ERROR

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

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

1. A change in engine RPM should be detected as each solenoid is cycled on.
2. If test light lights, PCM and wiring are okay.

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 connector 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.

1. Check for a restriction in EGR tube or passage. Also, ensure excessive carbon has not built up on EGR valve orifices.

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

Codes P1403/P1404/P1405 Schematic (3.4L) EGR Error. Scheme 96

Codes P1403/P1404/P1405 Diagnostic Flow Chart (3.4L) EGR Error. Scheme 97

CODE P1530, A/C PRESSURE SENSOR

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

Signal is a voltage which is proportional to pressure. Sensor's range of operation is zero to 454 psi. At zero psi, signal will be about .1 volt, varying up to about 4.9 volts at 454 psi or more. Code P1530 will set if voltage is greater than 4.9 volts (454 psi) or less than .3 volt (7.5 psi) for 5 or more seconds. A/C compressor clutch is disabled by PCM if fault is present.

Note. Test numbers refer to numbers on diagnostic chart.

1. This step checks voltage signal being received by PCM from A/C refrigerant pressure sensor.
2. Checks if high voltage signal is from a shorted sensor or a short to voltage in circuit. Normally, disconnecting sensor would make a normal circuit go to near zero volt.
3. Checks if low voltage signal is from sensor or circuit. Jumpering sensor circuits together checks circuit, connections and PCM.
4. This step checks if low voltage signal was due to an open in sensor circuit or 5-volt reference circuit since previous step eliminated pressure sensor.
5. The 5-volt reference for Throttle Position (TP) sensor connects to same 5-volt power supply in PCM. If 5-volt reference circuit to TP sensor has a short to ground, MAP sensor and A/C refrigerant pressure sensor 5-volt reference circuit will also have a short to ground because they connect to same power supply in PCM. A short to ground on either 5-volt reference circuit does not damage PCM's 5-volt power supply. When short is repaired, PCM's 5-volt supply will return to normal.

At temperatures of about -20°F and less, A/C pressure can drop below .3 volt (7.5 psi) threshold. If this happens, Code P1530 will set and disable A/C system. Clear Code P1530 and check A/C pressure in a heated garage. If A/C pressure is between .3 volt (7.5 psi) and 4.9 volts (454 psi), A/C pressure transducer is properly functioning.

Code P1530 sets when signal voltage falls outside normal possible range of sensor. If signal voltage is greater than .1 volt, but less than .3 volt, there could be a low refrigerant pressure problem with A/C system.

Code P1530 Schematic (3.4L) A/C Pressure Sensor. Scheme 98

Code P1530 Diagnostic Flow Chart (3.4L) A/C Pressure Sensor. Scheme 99

CODE P1550, CRUISE STEPPER MOTOR

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

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

If PCM detects any of these conditions, it will interrupt ground at cruise inhibit signal circuit to request that cruise control disengage.

Note. Test numbers refer to numbers on diagnostic chart.

1. Ensures PCM is detecting a current fault.
2. Ensures cruise status circuit is not open or grounded, or shorted to voltage, and proper voltage is being supplied by SMCC module.

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

1. Poor Connection Or Damaged Harness

Inspect PCM harness for open or short to voltage in status circuit, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection and damaged harness.

1. Intermittent Test

Observe SMCC status on scan tester while moving related connectors and wiring harness with engine running. If failure is induced, SMCC status display will change to engaged. This may assist in isolating location of malfunction.

Code P1550 Schematic (3.4L) Cruise Stepper Motor. Scheme 100

Code P1550 Diagnostic Flow Chart (3.4L) Cruise Stepper Motor. Scheme 101

CODE 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.

CODES P1626/1629, PASS-KEY II FUEL ENABLE CIRCUIT

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.

Code P1626 will set when the following condition is present.

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

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.

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.

Codes P1626/1629 Schematic (3.4L) Pass-Key II Fuel Enable Circuit. Scheme 102

Codes P1626/1629 Diagnostic Flow Chart (3.4L) Pass-Key II Fuel Enable Circuit. Scheme 103

CODE P1630, SYSTEM VOLTAGE HIGH/LOW

PCM monitors system voltage on PCM ignition feed terminal.

Code P1630 will set when the following condition is present.

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

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.

Code P1630 Schematic (3.4L) System Voltage High/Low. Scheme 104

Code P1630 Diagnostic Flow Chart (3.4L) System Voltage High/Low. Scheme 105

CODE P1640, QDM "A" ERROR

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

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

Code P1640 will set when the following conditions are present.

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

PCM will illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. PCM does not know which controlled circuit caused Code P1640. This chart will go through each of circuits to determine which is at fault. If QDM related codes are present, use applicable code chart first.
2. QDM "A" related code will include Code P0740.
3. QDM "A" symptoms: Cooling fan No. 2 always on or will not come on at all. Poor driveability due to 100 percent canister purge. TCC does not engage. Low oil light always on.
4. This test will determine if problem is circuit or component.
5. This test will determine which circuit is out of specification.
6. As factory installed PCM is protected with an internal circuit breaker, it is highly unlikely that PCM needs to be replaced.

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.

Code P1640 Schematic (3.4L) QDM "A" Error. Scheme 106

Code P1640 Diagnostic Flow Chart (3.4L) QDM "A" Error. Scheme 107

CODE P1650, QDM "B" ERROR

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 display on Tech 1. PCM will compare voltage at QDM based on accepted values of fault line. If QDM "B" fault detection circuit senses a voltage other than accepted value, fault line will go from a low signal on data stream to a high signal and Code P1650 will set. Code P1650 will set when the following conditions are present.

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

Code P1650 will not illuminate Malfunction Indicator Light (MIL).

Note. Test numbers refer to numbers on diagnostic chart.

1. PCM does not know which controlled circuit caused Code P1650. This chart will go through each circuit to determine which is at fault. If QDM related codes are present, use applicable code chart first.
2. If QDM "B" related symptoms are present, checks on Code P1650 (2 OF 2) chart should isolate cause of fault. QDM "B" symptoms: Improper shifting. TCC will not apply or TCC harsh engagement. Poor driveability due to EGR constantly on.
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.

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 P1650 Schematic (3.4L) QDM "B" Error. Scheme 108

Code P1650 Diagnostic Flow Chart (3.4L) QDM "B" Error. Scheme 109

SUMMARY

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

3.4L (VIN X) PCM Wiring Diagram (All Models - 1 Of 3). Scheme 110

3.4L (VIN X) PCM Wiring Diagram (All Models - 2 Of 3). Scheme 111

3.4L (VIN X) PCM Wiring Diagram (All Models - 3 Of 3). Scheme 112

See also:
• BASIC TESTING
• TESTS W/O CODES
• SYSTEM/COMPONENT TESTS - 3.4L
• HARD OR INTERMITTENT TROUBLE CODE DETERMINATION
• DATA LINK CONNECTOR (DLC) TEST TERMINALS
• SCAN TESTER USAGE
• SCAN DATA
• CODE P0101
• CODE P0112
• CODE P0113
• CODE P0117
• CODE P0118
• CODE 14
• CODE P0122
• CODE P0123
• CODE P0131
• CODE P0132
• CODE P0134
• CODE P0321
• CODE P0325
• CODE P0341
• CODE P0342
• CODE 55
• CODES P0501/P0502
• CODE P0703
• CODE P0705
• CODE P0712
• CODE P0713
• CODE P0740
• CODE P0755
• CODES P1350/P1361
• CODES P1403/P1404/P1405
• CODE P1530
• CODE P1550
• CODE P1623
• CODE 51 or
• CODE 52
• CODES P1626/1629
• CODE P1630
• CODE P1640
• CODE P1650
• CLEARING TROUBLE CODES