- Intermittent Malfunctions

DEFINITION
Problem may or may not light the Malfunction Indicator Lamp (MIL) or store a Diagnostic Trouble Code (DTC).

DIAGNOSTIC TROUBLE CODE CHARTS
DO NOT use the 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.

FAULTY ELECTRICAL CONNECTIONS OR WIRING
Most intermittent problems are caused by faulty electrical connections or wiring. Perform careful check of suspect circuits for:
- Poor mating of the connector halves, or terminals not fully seated in the connector body (backed out).
- Improperly formed or damaged terminals. All connector terminals in problem circuit should be carefully reformed or replaced to ensure proper contact tension.
- Poor terminal to wire connection. This requires removing the terminal from the connector body to check.

ROAD TEST
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.

INTERMITTENT MIL - NO DTC
An intermittent MIL with no stored DTC may be caused by:
- MIL wire to ECM shorted to ground.
- Diagnostic request terminal wire to ECM shorted to ground.
- ECM grounds. Refer to ECM wiring diagrams. Diagrams

ELECTRICAL INTERFERENCE
^ Check for electrical system interference caused by a defective relay, ECM 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.