Intermittent Condition Diagnosis

SYMPTOM DESCRIPTION:
An Intermittent problem is one that occurs at a very specific time, under a very specific condition. The degree of the problem is very wide ranged, and may last for a brief moment or a few miles. The Control Unit may not be able to detect or record a trouble code for an Intermittent problem, and in most cases the CHECK ENGINE light will not come ON, indicating a component/system failure.

1. Verify with the customer a detailed description of when the problem was first noticed, and the time(s) of its reoccurence.

2. If a visual/physical inspection does not narrow or locate the cause, perform a Diagnostic Circuit Check, making a note of any stored trouble codes. Once this is achieved, clear the Control Units memory prior to road testing. This will eliminate any false codes not related to the complaint.

3. If a particular circuit is suspected to be the cause, the vehicle can be driven with a voltmeter connected in series to that circuit.
An abnormal voltage or "Scan" reading, when the problem occurs, indicates that further inspection of that circuit is needed.

FAULTY ELECTRICAL CONNECTIONS OR WIRING
Most intermittent problems are caused by faulty electrical connections and/or wiring. Perform careful check of suspect circuits for:

1. Poor mating of electrical harness connector halves.
Wire terminals that have backed out of the connector body.

2. Improperly formed or damaged terminals.
Connector terminals should be carefully reformed or replaced to ensure proper contact with mating half.

3. Loose wire to terminal connections within the harness connectors. This would require removing the terminal from the connector body to verify and correct the problem wire.