- Intermittent Malfunctions

Important: Problem may or may not turn ON the Malfunction Indicator Lamp (MIL) or store a DTC. DO NOT use the Diagnostic Trouble Code (DTC) tables for intermittent problems. The fault must be present to locate the problem.

Most intermittent problems are caused by faulty electrical connections or wiring. Perform careful visual/physical check. Check for the following conditions:

^ Poor mating of the connector halves or a terminal not fully seated in the connector (backed out).

^ Improperly formed or damaged terminal.

^ All connector terminals in the problem circuit should be carefully checked for proper contact tension.

^ Poor terminal to wire connection. This requires removing the terminal from the connector body to check.

The vehicle may be driven with a J 39200 Digital Multimeter connected to a suspected circuit. An abnormal voltage when malfunction occurs is a good indication that there is a fault in the circuit being monitored.

A scan tool can be used to help detect intermittent conditions. The scan tool has several features that can be used to locate an intermittent condition.

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.

Using a scan tools Freeze Frame buffer can also aid in locating an intermittent condition. Review and record the information in the freeze frame associated with the intermittent DTC being diagnosed. The vehicle can be driven within the conditions that were present when the DTC originally set.

To check loss of DTC memory, disconnect Throttle Position (TP) sensor and idle engine until the MIL (Check Engine) comes ON. DTC P0122 should be stored and kept in memory when ignition is turned OFF. If not the PCM is faulty. When this test is completed, make sure that you clear the DTC P0122 from memory.

An intermittent MIL (Check Engine) with no stored DTC may be caused by the following:

^ Ignition coil shorted to ground and arcing at ignition wires or plugs.

^ MIL (Check Engine) wire to PCM shorted to ground.

^ Poor PCM grounds, go to PCM wiring diagrams.

If the intermittent condition exists as a start and then stall, check for DTC(s) relating to the vehicle theft deterrent system.

Check for an electrical system interference caused by a defective relay, PCM driven solenoid, or switch. They can cause a sharp electrical surge. Normally, the problem will occur when the faulty component is operated.

Check for improper installation of electrical options such as lights, cellular phones etc.

All Ignition Control Module (ICM) wiring should kept away from the generator. Check all wires from the PCM to the ignition control module for poor connections.

Check for open diode across A/C compressor clutch and check for other open diodes, Go to wiring diagrams.