Intermittant Check Procedure

"Intermittent" means that the "Check Engine" light comes on at times but does not stay on. Since codes may or may not be stored, the use of diagnostic charts could result in replacement of good parts.

Most intermittent problems are caused by faulty electrical wiring or connections. Carefully check these potential causes:

- Poor mating of connector halves or terminals not fully seated in connector body.
- Deformed 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 terminal from connector body to properly check.
- Poor ground connections.
- If a visual check does not find the source of the problem, the vehicle may be driven with a voltmeter connected to a suspect circuit. An abnormal voltage reading when the problem occurs indicates the problem may be in that circuit.

An intermittent "Check Engine" light with no stored code may be caused by:

- Arcing at ignition coil, plug wires or spark plugs.
- Faulty power supply main relay.
- Poor power supply circuit connections.
- "Check Engine" light wire to Engine Control Module (ECM) shorted to ground (circuit 22).
- Diagnostic test lead to ECM shorted to ground (circuit 24).
- Poor ECM ground connections at intake manifold.
- Electrical system interference caused by a defective relay, ECM driven solenoid or switch. These problems cause an electrical surge and normally occur when the faulty component is operated.
- Improper installation of accessories such as lights, sound systems, alarms, etc.