Intermittent Conditions

Important: 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 any intermittent problems. The fault must be present in order to locate the problem.

Most intermittent problems are caused by poor electrical connections or wiring. Perform a careful visual/physical check for the following conditions:
^ Poor mating of the connector halves or a terminal not fully seated in the connector (backed out)
^ An improperly formed or damaged terminal
^ All connector terminals in the problem circuit should be carefully checked for proper contact tension.
^ A poor terminal to wire connection-This requires removing the terminal from the connector body in order to check. Also, check for the terminal being crimped over the insulation.

Road test the vehicle with a J 39200 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.

The Tech 2 scan tool has several features that are useful for locating intermittent conditions. Use the following features in order to find the intermittent faults:
^ The Snapshot feature can be triggered to capture and store the engine parameters within the scan tool when the malfunction occurs. You can review this stored information in order to determine what caused the malfunction, or what conditions were present when the problem occurred.
^ Reviewing the Freeze Frame data can also aid in locating an intermittent condition. Review and record the information in the Freeze Frame that is associated with the intermittent DTC being diagnosed. The vehicle can be driven within the conditions that were present when the DTC originally set.

An intermittent MIL with no stored DTC may be caused by poor ECM grounds. Refer to the ECM wiring diagrams.

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

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

Check for an open diode across the A/C compressor clutch. Then, check for other open diodes.