- Intermittent Malfunctions

Problem may, or may not, turn "ON" the "CHECK ENGINE" light, or set a code.

DO NOT use the trouble code charts for intermittent problems. The fault must be present to locate the problem. If a fault is intermittent, use of trouble code charts may result in replacement of good parts.

^ Most intermittent problems are caused by faulty electrical connections or wiring. Perform careful check. Look 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 to increase contact tension.
- Poor terminal to wire connection. This requires removing the terminal from the connector body to check.

^ If a visual check does not find the cause of the problem, the car can be driven with a voltmeter connected to a suspected circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit. If the wiring and connectors check OK and a trouble code was stored for a circuit having a sensor, except for Codes 43, 44, and 45, substitute a known good sensor and recheck. A "Scan" tool can also be used by monitoring the suspected problem circuit while moving related wiring and connectors.

^ Check for intermittent connection in circuit from:
- Open ignition coil ground and arcing at spark plug wires or plugs.
- "CHECK ENGINE" light wire to ECM, for short to ground.
- Diagnostic "Test" terminal wire to ECM for short to ground.
- ECM terminals "A" and "U" to engine ground.

^ Check for loss of trouble code memory by grounding dwell lead during idle. This should cause a "CHECK ENGINE" light and Code 23 should be stored and kept in memory when ignition is turned off for at least 10 seconds. If voltage is present at ECM terminal "6" but no code is stored, the ECM is faulty.

^ Check for an 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.

^ Check for improper installation of electrical options such as lights, 2-way radios, etc.

^ Check for open diode or resistor across A/C compressor clutch and for other open diodes.