- Intermittent Malfunctions

INTERMITTENTS

Definition: Problem may or may not light the 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. If a fault is intermittent, use of DTC charts may result in replacement of good parts.

^ Most intermittent problems are caused by faulty electrical connections or wiring. Perform visual/physical checks. Check for:

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

- Improperly formed or damaged terminal. All connector terminals in the problem circuit should be carefully reformed or replaced to insure proper contact tension.

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

^ If a visual/physical check does not find the cause of the problem, the vehicle can be driven with a digital multimeter connected to a suspected circuit. An abnormal voltage reading, when the problem occurs, indicates the problem may be in that circuit.

^ An intermittent MIL with no stored DTC may be caused by:

- MIL wire to ECM/PCM shorted to ground.

- Diagnostic request terminal wire to ECM/PCM shorted to ground.

- ECM/PCM grounds refer to ECM/PCM wiring diagrams.

^ Check for electrical system interfence caused by a defective relay, ECM/PCM driven component, 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, two-way radios, etc.

^ Ignition wires should be routed away from spark plug wires. distributor wires, distributor housing, coil and generator.