- Intermittent Malfunctions

Definition: Problem may or may not activate the "Check Engine" light or store a trouble code.

DO NOT use the trouble code charts in Section "A" for intermittent problems. The fault must be present to locate the problem. If a fault is intermittent, the use of trouble code charts may result in the replacement of good parts.
^ Most intermittent problems are caused by faulty electrical connections or wiring. Perform careful checks of suspected circuits for Poor mating of the connector halves and 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 to increase contact tension.
- Poor terminal to wire connection. This requires removing the terminal from the connector body to check as outlined in the introduction.
^ If a visual and physical check does not locate the cause of the problem, the vehicle can be driven with a voltmeter connected to a suspected circuit or a "Scan" tool may be used. An abnormal voltage reading while the problem occurs indicates that the problem may be in that circuit.
^ Check for loss of trouble code memory. To check, disconnect the TPS and allow the engine to idle until the "Check Engine" light turns "ON." Code 22 should be stored and kept in memory when the ignition is turned "OFF" for at least 10 seconds. If not, the ECM is faulty.
^ An intermittent "Check Engine" light and no trouble codes may be caused by
- Electrical system interference caused by a defective relay, ECM driven solenoid, or switch. They can cause a sharp electrical surge. Normally, the problem will occur when the faulty component is operated.
- Improper installation of electrical options, such as lights, 2-way radios, etc.
- EST wires which should be routed away from spark plug wires, ignition system components, and generator. Ground wire from ECM to ignition system which may be faulty.
- Ignition secondary wire shorted to ground.
- "Check Engine" light and diagnostic "test" terminal circuits intermittently shorted to ground.
- Faulty ECM grounds.