Intermittent Incident Testing

Intermittent Problem Simulation:

SIMULATING CONDITIONS
In order to duplicate an intermittant problem, it is effective to create similar conditions under which the fault may occur.

Intermittent Problem Simulation:

To imitate the specific conditions under which a problem may occur, perform the procedure listed under service procedure and note the result.

ON BOARD DIAGNOSIS
Using the on board self diagnosis utility will allow checking for intermittant problems in certain circuits.

SYMPTOM DESCRIPTION
Problems may or may not turn "ON" the Malfunction Indicator Light (MIL) or store a code.

FAULTY ELECTRICAL CONNECTIONS OR WIRING
Most intermittent problems are caused by faulty electrical connections or wiring. Perform careful check of suspect circuits for
- Signs of moisture at terminal connectors or relay boxes.
- 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 or replaced to insure proper contact tension.
- Poor terminal to wire connection. This requires removing the terminal from the connector body to check.

ROAD TEST
If a visual/physical check does not find the cause of the problem, the vehicle 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 checkout OK, and a Diagnostic Trouble Code (DTC) was stored for a circuit having a sensor, replace the suspect sensor. If an abnormal voltage reading is detected, the wiring and connectors being OK, and no DTC's were set in fault memory, the Electronic Control Module (ECM) may be defective.

NOTE: It would be advantageous to make note of any stored DTC's and clear the ECM memory prior to road testing. This may eliminate any false codes not related to the complaint.

INTERMITTENT "MIL" ACTIVATION
An intermittent MIL activation with out Diagnostic Trouble Codes being stored could be caused by:
- Low battery voltage
- Poor electrical connections (loose, corroded, moisture).
- Electrical system interference caused by a defective relay, ECM driven solenoid, or switch. These components can cause a sharp electrical surge. Normally the problem will occur when the faulty component is operated.
- Improper installation of electrical devices, such as lights, mobile phones, 2-way radios, electric motors....etc.
- ECM grounds.

LOSS OF DTC MEMORY
Loss of DTC memory may be caused by:
- Low battery voltage
- Loss of power to the ECM
- Defective ECM