Engine Control System Troubleshooting - No Codes: Other Pontiac Bonneville X

Possible Cause & Correction

Check the following items

1. Check ignition wires for short or faulty insulation. Spray spark plug wires with a fine mist of water to check for shorts.
2. Using Spark Tester (J-26792), check for available secondary voltage.
3. Check ignition system for faulty ground and power feed circuits.
4. Ensure ignition control wiring harness is not routed too close to wiring which may cause induced voltage signals.
5. Check Transaxle Range (TR) switch input with vehicle in drive and shifter in drive or overdrive.
6. Remove spark plugs and check for correct heat range, wear, cracks, wetness, improper gap or heavy deposits.
7. Check for poor quality or alcohol contaminated fuel.
8. Check for improper fuel pressure. Check for restricted fuel filter. See FUEL SYSTEM PRESSURE TEST under BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
9. Check for plugged injectors. Perform injector balance test. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.
10. Check PCM for proper ground circuits. Check for internal PCM intermittents.
11. Check engine compression. Check for incorrect valve timing, bent push rods, broken valve springs or worn camshaft lobes.
12. Check for sticking EGR valve.
13. Check TP sensor for sticking and binding. Check for correct TP sensor voltage. See FUEL SYSTEMS in appropriate SERVICE & ADJUSTMENT SPECIFICATIONS article.
14. Using a scan tool, monitor the Knock Sensor (KS) system for any excessive spark retard activity.
15. Check MAF sensor and connections.
16. Check for proper Crankshaft Position (CKP) and Camshaft Position (CMP) sensor resistance.
17. Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter.
18. Check for faulty motor mounts.
19. Check injector drivers by disconnecting all injector harness connectors and connecting an injector test light (noid light) to each injector's harness terminal. Light should flash while cranking.
20. Check intake and exhaust manifold passages for casting flash.
21. Check PCM and engine grounds for correct locations, tight and clean connections. See WIRING DIAGRAMS article.

Check the following items

1. Check TP sensor adjustment and operation.
2. Check fuel system. Perform BASIC FUEL SYSTEM CHECKS. See appropriate BASIC DIAGNOSTIC PROCEDURES article.
3. Check fuel injectors. Perform injector balance test. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.
4. Check Knock Sensor (KS) system for no retard.
5. Check EGR system (insufficient).
6. Check Torque Converter Clutch (TCC) system operation (applying too soon).
7. Remove carbon from engine with top engine cleaner.
8. If excessive carbon exists in combustion chamber, check for excessive oil burning due to leaking valve guide seals.
9. Check for incorrect basic engine parts such as camshaft, cylinder heads and pistons.
10. Ensure the installed PCM program is correct for the particular vehicle. Check with dealer for latest application information.
11. Check for low engine coolant.
12. Check cooling fan for proper operation.
13. Check for restricted airflow to radiator or restricted coolant flow through radiator.
14. Check for loose water pump belt.
15. Check engine coolant sensor for shift in calibration. See appropriate SENSOR OPERATING RANGE CHARTS article.
16. Check for rich or lean running conditions.
17. Using Spark Tester (J-26792), check available output voltage of ignition coil.
18. Check for crossfire between spark plugs and spark plug wires. Check for shorts and faulty insulation by spraying spark plug wires with a fine water mist.
19. Check spark plugs for proper application and heat range.
20. Check engine compression.
21. Check Transaxle Range (TR) switch. Ensure scan tool indicates proper gear range as selected.
22. Check for alcohol contaminated or poor quality fuel.
23. Check vehicle operation using a higher octane fuel (minimum 87 octane).

Check the following items

1. Check for incorrect valve timing, bent push rods, broken valve springs or worn camshaft lobes.
2. Check for sticking or leaking valves.
3. Check EGR valve for leaking base gasket or valve hanging open.
4. Check for engine vacuum leaks and/or engine not tuned to specifications.
5. Check ignition module ground and power feed circuits for poor or loose connections.
6. Check air induction system for restrictions or air leaks. Also check for air leaks between Mass Airflow (MAF) sensor and throttle body. Check MAF sensor for proper operation.
7. Check fuel injectors. Perform injector balance test. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.
8. Check fuel system. Perform BASIC FUEL SYSTEM CHECKS. See appropriate BASIC DIAGNOSTIC PROCEDURES article.
9. Using Spark Tester (J-26792), check available output voltage of ignition coil.
10. Check for crossfire between spark plugs and spark plug wires.
11. Remove spark plugs and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits. Also, check condition of spark plug wires. Spray spark plug wires with a fine mist of water to check for shorts.
12. Check for proper Crankshaft Position (CKP) and Camshaft Position (CMP) sensor resistance.
13. Check ignition system for faulty ground and power feed circuits.
14. Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter.
15. Check intake and exhaust manifold passages for casting flash.
16. Check harmonic balancer interrupter rings for missing, broken or bent vanes.
17. Check for a low engine coolant level.
18. Check the engine thermostat for the correct operation and heat range.
19. Test the Torque Converter Clutch (TCC).
20. Check the charging system. A bad diode in the alternator can allow A/C noise to enter the electrical system. This may affect the engine controls system operation.
21. Check the transaxle range switch circuit and be sure the scan tool indicates the vehicle is in drive with the gear selector in Drive or in Overdrive.

Check the following items

1. Check for leaking fuel injectors. Perform injector balance test. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.
2. Check for alcohol contaminated fuel, correct fuel pressure or a restricted fuel injector.
3. Check for fuel in pressure regulator vacuum hose. Replace pressure regulator if fuel is present.
4. Check injector harness locations. Ensure injectors are connected to correct injector/cylinder according to firing order.
5. Check for faulty PCV valve.
6. Check Idle Air Control (IAC) system. Check for vacuum leak or high idle. Check for foreign material in IAC bore of throttle body. Check for proper connection of IAC valve electrical connector.
7. Check for short between battery voltage and ignition feed circuits. See WIRING DIAGRAMS article.

Check the following items

1. Check fuel pump relay by connecting test light between fuel pump relay connector ignition feed circuit and ground. Turn ignition on. Light should illuminate for 2 seconds. If light does not illuminate for 2 seconds, see RELAYS under MODULES, RELAYS & SOLENOIDS in appropriate SYSTEM & COMPONENT TESTING article. For location of fuel pump test connector, see COMPONENT LOCATIONS in appropriate SYSTEM & COMPONENT TESTING article.
2. Check for open injector fuse(s).
3. Check for poor quality or alcohol contaminated fuel.
4. Check for binding or sticking TP sensor, or high TP sensor voltage with throttle closed.
5. Check EGR operation.
6. Check for leaking fuel injector.
7. Ensure resistance of Engine Coolant Temperature (ECT) sensor circuit is within specification. See appropriate SENSOR OPERATING RANGE CHARTS article.
8. Check resistance of ECT and Intake Air Temperature (IAT) sensors. On a cold engine, ECT and IAT sensor readings should be within 5°F of each other.
9. Check for proper spark output using Spark Tester (J-26792).
10. Remove spark plugs and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits.
11. Check fuel pressure. See FUEL SYSTEM PRESSURE TEST under BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
12. Check for plugged injectors. Perform injector balance test. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.
13. Check for loose ignition coil ground and power feed circuit connections. Also check ignition coil fuse.
14. Check for faulty in-tank fuel pump check valve (if equipped). A faulty in-tank fuel pump check valve will allow fuel to drain back to tank after engine is stopped. To check this condition, turn ignition off, disconnect fuel pressure line at fuel rail and remove filler cap. Using a radiator pressure tester, apply 15 psi (1.0 kg/cm 2 ). If pressure holds for 60 seconds, check valve is okay.
15. Ensure the installed PCM program is correct for the particular vehicle. Check with dealer for latest application information.
16. Check for restricted exhaust system, such as a damaged or collapsed pipe, muffler or catalytic converter.
17. Check Idle Air Control (IAC) system. Check for vacuum leak at high idle. Check for binding of throttle blade or linkage. Check for foreign material in IAC bore of throttle body. Check for proper connection of IAC valve electrical connector. Check for failure of A/C compressor or relay.
18. Check Manifold Absolute Pressure (MAP) and/or Mass Airflow (MAF) sensor. Check air intake tube for air leaks, blockage or damage.
19. Inspect Crankshaft Position (CKP) sensor clearance and resistance. Check harmonic balancer interrupter rings for bent or missing vanes.
20. Check if PCV valve is stuck open.
21. Using a scan tool, check the Idle Air Control (IAC) operation.
22. Check basic engine mechanical problems (i.e., compression, head gasket(s), valves). Check for incorrect valve timing, bent push rods, broken valve springs or worn camshaft lobes.
23. Check PCM and engine grounds for correct locations, tight and clean connections. See WIRING DIAGRAMS article.

Check the following items

1. Visually check vacuum hoses for splits, kinks and proper connections as shown on vehicle emission control information label.
2. Check ignition wires for cracking, hardness and proper connections at spark plugs. Spray spark plug wires with a fine mist of water to check for shorts.
3. Check wires for pinches, cuts and proper connections.
4. Check fuel pressure. See FUEL SYSTEM PRESSURE TEST under BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
5. Check for poor quality or alcohol/water contaminated fuel.
6. Check for fouled spark plugs.
7. Ensure the installed PCM program is correct for that particular vehicle. Check with dealer for latest application information.
8. Check for a binding or sticking TP sensor. Voltage should increase steadily as throttle is moved toward Wide Open Throttle (WOT). Also check related wiring.
9. Ensure PCM-controlled idle speed is correct.
10. Check EGR operation.
11. Check engine cooling system thermostat for proper operation and heat range.
12. Check ignition control system ground and power feed circuits.
13. Check canister purge system for proper operation.
14. Check charging system output. Repair charging system if voltage is less than 9 volts or more than 16 volts.
15. Check fuel injectors. Perform injector balance test. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.
16. Check injector harness locations. Ensure injectors are connected to correct injector/cylinder according to firing order.
17. Check for proper Crankshaft Position (CKP) and Camshaft Position (CMP) sensor resistance. Check for intermittent ignition feed or ground circuits.
18. Check Heated Oxygen Sensor (HO2S) ground (corroded threads in exhaust manifold or pipe).
19. Check for air leaks between Mass Airflow (MAF) sensor and throttle body.
20. Check air induction system for damage, restriction or air leaks.
21. Check for intake valve deposits.
22. Check Manifold Absolute Pressure (MAP) and MAF sensor values and related wiring.
23. Check for excessive exhaust system backpressure.
24. Check for proper operation of the Transmission Fluid Pressure (TFP) manual valve switch.

Check the following items

1. Ensure air filter and fuel filter are not plugged. Replace if necessary. Check for incorrect fuel pressure. Also check for contaminated fuel.
2. Check shift solenoid system and Torque Converter Clutch (TCC) system for proper operation.
3. Check Knock Sensor (KS) system for excessive retard.
4. Check ignition control system for proper operation.
5. Check the spark plugs.
6. Check the fuel pressure. See FUEL SYSTEM PRESSURE TEST under BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
7. Check for plugged injectors. Perform injector balance test. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.
8. Ensure EGR valve is not open all the time.
9. Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter.
10. Check charging system output. Repair charging system if voltage is less than 9 volts or more than 16 volts.
11. Check for A/C clutch cutout at Wide Open Throttle (WOT).
12. Check Manifold Absolute Pressure (MAP) sensor.
13. Using Spark Tester (J-26792), check for available secondary voltage.
14. Check air induction system for restrictions or air leaks.
15. Ensure the installed PCM program is correct for the particular vehicle. Check with dealer for latest application information.
16. Check engine compression. Check for incorrect valve timing, bent push rods, broken valve springs or worn camshaft lobes.
17. Check for excessive fuel additives.
18. Check for binding accelerator cable.
19. Check engine supercharger (if equipped).
20. Check if engine is operating in torque management mode (if equipped).
21. Check boost control system components and connections (if equipped).
22. Check for proper operation of the Transmission Fluid Pressure (TFP) manual valve switch.
23. Check PCM and engine grounds for correct locations, tight and clean connections. See WIRING DIAGRAMS article.

Check the following items

1. Visually check vacuum hoses for splits, kinks and proper connections as shown on vehicle emission control information label.
2. Check for dirty or clogged air filter.
3. Check coolant level. Check engine cooling system thermostat for proper heat range and operation.
4. Check engine compression. Check for incorrect valve timing, bent push rods, broken valve springs or worn camshaft lobes.
5. Check Engine Coolant Temperature (ECT) sensor for shift in calibration. See appropriate SENSOR OPERATING RANGE CHARTS article.
6. Check A/C for "full time" operation.
7. Ensure initial ignition timing is properly set, and check for proper operation of ignition control and knock sensor systems.
8. Check Torque Converter Clutch (TCC) for proper operation.
9. Check air intake system and crankcase for air leaks.
10. Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter.
11. Check Heated Oxygen Sensor (HO2S) for silicone or lead contamination.
12. Check for proper ignition voltage output. Check the ignition coils for cracks, or damage.
13. Remove spark plugs and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits.
14. Ensure speedometer is properly calibrated.
15. Check fuel pressure. See FUEL SYSTEM PRESSURE TEST under BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
16. Check for poor quality or alcohol contaminated fuel.
17. Check fuel injectors. Perform injector balance test. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.
18. Check injector harness locations. Ensure injectors are connected to correct injector/cylinder according to firing order.
19. Check for fuel in pressure regulator vacuum hose. If fuel is present, replace regulator.
20. Check Camshaft Position (CMP) and Crankshaft Position (CKP) sensors for proper operation.
21. Check for air leaks between Mass Airflow (MAF) sensor and throttle body. Check air induction system for damage, restriction or air leaks.
22. Check boost control system (if equipped).
23. Check engine compression.
24. Check the exhaust system for possible restrictions.
25. Check for dragging brakes.
26. Check for conditions that cause the engine torque management system to reduce engine power.
27. Check for incorrect tire pressure.
28. Check for uneven or excessive tire wear from suspension misalignment.
29. Check with operator to see if vehicle is operated under excessive acceleration or is heavily loaded.

Check the following items

1. Fill limiter vent valve stuck closed.
2. EVAP canister restricted.
3. EVAP vent valve stuck closed.
4. Restricted vapor lines.
5. High reid vapor pressure or high fuel temperature.
6. Fuel filler hose is pinched or kinked.
7. Ignition switch on (EVAP vent valve closed).

Check the following items

1. Pressure relief valve is stuck open or leaking.
2. Fill limiter vent valve is stuck open or leaking.

Cause & Correction

Check the following items

1. Fill limiter vent valve stuck closed.
2. EVAP canister restricted.
3. EVAP vent valve stuck closed.
4. Restricted vapor lines.
5. High reid vapor pressure or high fuel temperature.
6. Ignition switch on (EVAP vent valve closed).

Check the following items

1. The check valve is stuck open.
2. The check valve is stuck closed.
3. The check valve is leaking.
4. High reid vapor pressure or high fuel temperature.
5. Ignition switch on (EVAP vent valve closed).

Check the following items

1. Fill limiter vent valve stuck open or leaking.

Check the following items

1. The pressure relief valve in the fill limiter vent valve is stuck open or leaking.
2. Fuel filler pipe loose or ruptured.
3. The fill limiter vent valve is stuck open.

Check the following items

1. The pressure relief valve in the fuel limiter vent valve is stuck open or leaking.
2. The EVAP canister is saturated.

Check the following items

1. Ensure throttle linkage and/or TP sensor is not sticking or binding. Ensure throttle bore is free of foreign material.
2. Check for vacuum leaks.
3. Check engine idle speed (both base idle and PCM idle).
4. Check Idle Air Control (IAC) system. Check for vacuum leak or high idle. Check for alcohol contaminated fuel, incorrect fuel pressure or a restricted injector. Check for foreign material in IAC bore of throttle body. Check for proper connection of IAC valve electrical connector. Check for failure of A/C compressor or relay.
5. Check for proper operation of EGR system.
6. Check Transaxle Range (TR) switch circuit. Ensure TR switch is properly adjusted.
7. Check Power Steering Pressure (PSP) switch operation.
8. Check charging system output. Repair charging system if voltage is less than 9 volts or more than 16 volts.
9. Check for fuel in pressure regulator vacuum hose. If fuel is present, replace regulator.
10. Check evaporative emission control system.
11. Check for proper spark plug gap.
12. Check PCM grounds for clean and tight connections.
13. Check A/C signal to PCM. If problem exists only when A/C is on, check A/C system operation and pressures.
14. Ensure the installed PCM program is correct for the particular vehicle. Check with dealer for latest application information.
15. Check Manifold Absolute Pressure (MAP) or Mass Airflow (MAF) sensors for proper operation.
16. Check Heated Oxygen Sensor (HO2S) operation. Check for silicone contamination or incorrect RTV sealant.
17. Check for excessive fuel additives.
18. Check for shorted or open injector windings.
19. Check for leaking injectors. Perform injector balance test. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.
20. Check injector harness locations. Ensure injectors are connected to correct injector/cylinder according to firing order.
21. If rough idle only occurs when engine is hot, check PCV valve operation. Check for manifold vacuum at inlet end of crankcase vent tube assembly with engine idling.
22. Using a scan tool, monitor the Knock Sensor (KS) system for any excessive spark retard activity.
23. Test the crankcase ventilation valve for proper operation. Place a finger over the inlet hole of the valve end several times. The valve should snap back. If not, replace the valve.
24. Check ignition system. Check for moisture, dust, cracks, burns, etc. Check for shorts and faulty insulation by spraying spark plug wires with a fine water mist.
25. Using Spark Tester (J-26792), check for available secondary voltage.
26. Check to see if condition is caused by engine running either rich or lean.
27. Check engine compression. Check for incorrect valve timing, bent push rods, broken valve springs or worn camshaft lobes.
28. Check Engine Coolant Temperature (ECT) sensor for proper temperature-to-resistance values.
29. Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter.
30. Check the Torque Converter Clutch (TCC) operation. A scan tool should indicate an RPM drop when the TCC is commanded ON.
31. Check the charging system. A bad diode in the alternator can allow A/C noise to enter the electrical system. This may affect the engine controls system operation.
32. Check the transaxle range switch circuit. Ensure the scan tool indicates the vehicle is in drive with the gear selector in Drive or in Overdrive.
33. Check for weak or broken motor mounts.

Check the following items

1. Visually check vacuum hoses for splits, kinks and proper connections as shown on vehicle emission control information label.
2. Check canister purge system for proper operation.
3. Check ignition control system for proper operation.
4. Check EGR system for proper operation.
5. Ensure the installed PCM program is correct for that particular vehicle. Check with dealer for latest application information.
6. Check for proper ignition voltage output using Spark Tester (J-26792).
7. Check Heated Oxygen Sensor (HO2S) for contamination. This will cause a false high voltage signal to PCM. PCM will respond by leaning out air/fuel ratio.
8. Check in-line fuel filter, and replace if dirty or clogged.
9. Check fuel pressure while condition exists. See FUEL SYSTEM PRESSURE TEST under BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
10. Check for poor quality or alcohol contaminated fuel.
11. Check Mass Airflow (MAF) sensor for proper operation. Check air induction system for damage, restriction or air leaks. See DIAGNOSTIC TESTS in appropriate SELF-DIAGNOSTICS article.
12. Remove spark plugs and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits. Also, check condition of spark plug wires. Spray spark plug wires with a fine mist of water to check for shorts.
13. Check charging system output. Repair charging system if voltage is less than 9 volts or more than 16 volts.
14. Check for restricted exhaust system, such as a damaged or collapsed pipe, muffler or catalytic converter.
15. Check transmission shift solenoid system and Torque Converter Clutch (TCC) system for proper operation.
16. Ensure owner understands operation of TCC and A/C clutch operation, as stated in owners manual.
17. Check injector harness locations. Ensure injectors are connected to correct injector/cylinder according to firing order.
18. Check for rich or lean conditions. Drive vehicle at speed when complaint occurs. See appropriate HO2S DTCs for diagnostic aids. See appropriate SELF-DIAGNOSTICS article.
19. Check for plugged injectors. Perform injector balance test. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.
20. Ensure PCM grounds are clean and tight.
21. Check for excessive use of additives in fuel.
22. Ensure that the engine coolant temperature is not above 266°F (130°C). This condition causes the PCM to operate in Engine Coolant Over Temperature-Fuel Disabled Mode. While in Engine Coolant Over Temperature-Fuel Disabled Mode, the PCM turns fuel OFF to 4 cylinders at a time in order to keep engine temperatures from reaching damaging levels. The system perceives Engine Coolant Over Temperature-Fuel Disabled Mode as a lack of power, a miss, or a rough idle.

INTERMITTENTS

PRELIMINARY

Perform the Diagnostic System Check-Engine Controls before starting. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS in appropriate SELF-DIAGNOSTICS article.

CONTROL MODULE POWER & GROUNDS, & COMPONENT POWER & GROUNDS

Poor power or ground connections can cause widely varying symptoms.

1. Test all control module power circuits. Many vehicles have multiple circuits supplying power to the control module. Other components in the system may have separate power circuits that may also need to be tested. Inspect connections at the module or component connectors, fuses, and any intermediate connections between the power source and the module or component. A test lamp or a Digital Multimeter (DMM) may indicate that voltage is present, but neither tests the ability of a circuit to carry sufficient current. Ensure that the circuit can carry the current necessary to operate the component. See POWER DISTRIBUTION article in WIRING DIAGRAMS.
2. Test all control module ground and system ground circuits. The control module may have multiple ground circuits. Other components in the system may have separate grounds that may also need to be tested. Inspect grounds for clean and tight connections at the grounding point. Inspect the connections at the component and in splice packs, where applicable. Ensure that the circuit can carry the current necessary to operate the component. See GROUND DISTRIBUTION article in WIRING DIAGRAMS.

TEMPERATURE SENSITIVITY

1. An intermittent condition may occur when a component or connection reaches normal operating temperature. The condition may occur only when the component or connection is cold, or only when the connection is hot.
2. The following data may help to diagnose this type of intermittent condition: Freeze Frame/Failure Records. Scan tool snapshot. Vehicle data recorder.
3. If the intermittent is related to heat, review the following data: High ambient temperatures. Underhood or engine generated heat. Circuit generated heat due to a poor connection, or high electrical load. Higher than normal load conditions, such as towing.
4. If the intermittent is related to cold, review the following data: Low ambient temperatures. In extremely low temperatures, ice may form in a connection or component. Test for water intrusion. The condition only occurs on a cold start. The condition is not present after the vehicle warms up.
5. Information from the customer may help to determine if the trouble follows a pattern that is temperature related.

INCORRECT PCM PROGRAMMING

1. There are only a few situations when reprogramming a PCM is appropriate, such as the following: A new service PCM is installed. A PCM from another vehicle is installed. Revised software or calibration files have been released for this vehicle.
2. Verify that the PCM contains the correct software or calibration. If incorrect programming is found, reprogram the PCM with the most current software or calibration. See POWERTRAIN CONTROL MODULE under PROGRAMMING in appropriate SELF-DIAGNOSTICS article.

DUPLICATING FAILURE CONDITIONS

1. If none of the previous tests are successful, attempt to duplicate or capture the failure conditions.
2. Freeze Frame/Failure Records data, where applicable, contains the conditions that were present when the DTC set. Perform the following procedure: Review and record Freeze Frame/Failure Records data. Clear the DTCs using the scan tool. Turn the key to OFF and wait 15 seconds. Operate the vehicle under the same conditions that were noted in Freeze Frame/Failure Records data, as closely as possible. The vehicle must also be operating within the Conditions for Running DTC. Monitor DTC Status for the DTC being tested. The scan tool will indicate Ran, when the enabling conditions have been satisfied long enough for the DTC to run. The scan tool will also indicate whether the DTC passed or failed.
3. An alternate method is to drive the vehicle with the Digital Multimeter (DMM) connected to a suspected circuit. An abnormal reading on the DMM when the problem occurs, may help you locate the problem.

VEHICLE DATA RECORDER

The Vehicle Data Recorder (J 42598) is connected to the Data Link Connector (DLC) and sent with the customer. The J 42598 captures data for later retrieval and analysis by the technician. Refer to the vehicle data recorder user instructions for more information.