- Intermittent Malfunctions

Definition

The problem may or may not turn "ON" the Malfunction Indicator Lamp (MIL) or store a Diagnostic Trouble Code (DTC).

Preliminary Checks

^ Refer to "Important Preliminary Checks." Testing and Inspection

^ Do Not use the DTC tables for intermittent problems. The fault must be present to locate the problem. If a fault is intermittent, the use of DTC tables may result in the replacement of good parts.

Faulty Electrical Connections or Wiring

Faulty electrical connections or wiring can cause most intermittent problems. Perform a careful check of the suspected circuit for the following:

^ Poor mating of the connector halves, or terminals, not fully seated in the connector body (backed out).

^ Improperly formed or damaged terminals, carefully reform or replace all the connector terminals in the problem circuit to insure the proper contact tension.

^ Poor terminal to wire connection, this requires removing the terminal from the connector body to check. Refer to Diagrams.

Road Test

If a visual/physical check does not locate the cause of the problem, drive the vehicle with a voltmeter connected to a suspected circuit or use a scan tool. If the wiring and connectors check OK, and a DTC was stored for a circuit having a sensor, replace the sensor.

Intermittent "Malfunction Indicator Lamp (MIL)

The following can cause an intermittent MIL and no DTCs:

^ 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 operating.

^ The improper installation of electrical devices, such as lights, 2-way radios, electric motors, etc.

^ Route the Ignition Control (IC) wires away from the spark plug wires, the ignition system components and the generator. The wire for the engine ground from the PCM to the ignition system should be a good ground.

^ The ignition secondary shorted to ground.

^ The Malfunction Indicator Lamp (MIL) circuit or the diagnostic "test" terminal intermittently shorted to ground.

^ The PCM grounds. Refer to the "PCM Wiring Diagrams."

Loss of DTC Memory

To check, disconnect the Throttle Position (TP) sensor and idle the engine until the "Malfunction Indicator Lamp" comes "ON." A DTC should store and remain in memory when turning "OFF" the ignition for at least 10 seconds.