For 1990-2009 cars

Important: The problem may or may not turn on the Service Vehicle Soon indicator or store a DTC. DO NOT use the diagnostic trouble code (DTC) tables for intermittent problems. The fault must be present in order to locate the problem.

Faulty electrical connections or wiring cause most intermittent problems. Perform a careful visual/physical inspection. Inspect for the following conditions:

• | Poor mating

• | The connector halves not fully seated in the connector (backed out)

• | A terminal not fully seated in the connector (backed out)

• | Improperly formed terminal

• | Damaged terminal

• | Proper contact tension

| Carefully inspect all of the connector terminals in the problem circuit.

• | Poor terminal to wire connection

| Remove the terminal from the connector body in order to inspect the connection.

The vehicle may be driven with J 39200 Digital Multimeter connected to a suspended circuit. An abnormal voltage when the malfunction occurs is a good indication that there is a fault in the circuit being monitored.

Use a scan tool in order to help detect intermittent conditions. The scan tool has several features that you may use in order to locate an intermittent condition.

In order to verify the loss of DTC memory, complete the following steps:

1. Disconnect the headlamps.
2. Idle the engine until the Service Vehicle Soon indicator turns on.

A number of DTCs should be stored and kept in memory when the ignition switch is turned to the OFF position. If the DTCs are not stored and kept in memory, the body control module (BCM) is faulty. When this test is completed, ensure that you clear the DTCs from the memory.

The following problems may cause an intermittent Service Vehicle Soon indicator with no stored DTC:

• | The ignition coil may have shorted to ground, and be arcing at the ignition wires.

• | Poor instrument cluster and BCM grounds.

| For information regarding these areas, refer to instrument cluster and BCM wiring diagrams.

Inspect for an electrical system interference. One of the following conditions may be the cause of the interference:

• | A defective relay

• | A defective PCM driven solenoid

• | A defective switch

These electrical system interferences may cause a sharp electrical surge. Normally, the problem will occur when the faulty component is located.

Inspect for proper installation of the following electrical options:

• | The lights

• | The cellular phones

• | Other electrical options

All ignition control module (ICM) wiring should be kept away from the generator.

Inspect for an open diode across the A/C compressor clutch. Inspect for other open diodes.