A problem may or may not turn ON the malfunction indicator lamp (MIL) or store a DTC. DO NOT use the diagnostic trouble code (DTC) charts for intermittent problems. The fault must be present to locate the problem.
Most intermittent problems are caused by faulty electrical connections or wiring. Inspect for the following conditions:
| • | Poor mating of the connector halves |
| • | A backed out terminal that is not fully seated in the connector |
| • | Improperly formed or damaged terminal |
| • | Poor terminal to wire connection--This requires removing the terminal from the connector body to check. |
All connector terminals in the problem circuit should be carefully checked for proper contact tension.
Road test the vehicle with a DMM connected to a suspected circuit. An abnormal voltage when a malfunction occurs is a good indication that there is a fault in the circuit being monitored.
Use a scan tool in order to help detect intermittent conditions. The scan tool has several features that can be used in order to locate an intermittent condition. Use the following features to find intermittent faults:
| • | The snapshot feature can be triggered to capture and store engine parameters within the scan tool when the malfunction occurs. This stored information then can be reviewed by the service technician to see what caused the malfunction. |
| • | Use the Freeze Frame/Failure Records data from the scan tool in order to locate an intermittent condition. Review and record the information in the Freeze Frame/Failure Record associated with the intermittent DTC being diagnosed. The vehicle may be driven within the conditions that were present when the DTC originally set. |
To test the loss of diagnostic code memory, disconnect the manifold absolute pressure (MAP) sensor and idle engine until the Service Engine Soon MIL comes ON. DTC P0107 should be stored and kept in memory when ignition is turned OFF. If not, the powertrain control module (PCM) is faulty. When this test is completed, ensure that you clear the DTC P0107 from memory.
An intermittent Service Engine Soon MIL with no stored DTC, may be caused by the following conditions:
| • | The ignition coil shorted to ground and arcing at ignition wires or plugs |
| • | The Service Engine Soon MIL wire to PCM shorted to ground |
| • | Poor PCM grounds--Refer to Engine Controls Schematics . |
Check for improper installation of electrical options such as lights, cellular phones etc. Route ignition control (IC) module wiring away from secondary ignition wires and ignition coils . Check all wires from the PCM to the ignition control module for poor connections.
Check for an open diode across the A/C compressor clutch and check for other open diodes.
