Intermittents

IMPORTANT: The problem may or may illuminate the Malfunction Indicator Lamp (MIL) or store a Diagnostic Trouble Code (DTC). Do not use the DTC tables for intermittent problems. The fault must be present to locate the problem.

Most intermittent problems are caused by faulty electrical connections or wiring. Perform a careful visual/physical check Check for the following conditions:
- Poor mating of the connector halves or a terminal not fully seated in the connector.
- Improperly formed or damaged terminal.
- All connector terminals in the problem circuit should be carefully checked for proper contact tension.
- Poor terminal-to-wire connection. This requires removing the terminal from the connector body to check.

The vehicle may be driven with a Digital Voltmeter (DVM) connected to the suspected circuit. An abnormal voltage when a malfunction occurs is a good indication that there is a fault in the circuit being monitored.

A scan tool can be used to help detect intermittent conditions

Using a scan tool's Freeze Frame buffer can aid in locating an intermittent condition. Review and record the information in the freeze frame associated with the intermittent DTC being diagnosed. The vehicle can be driven within the conditions that were present when the DTC originally set.

To check loss of DTC memory, disconnect the Throttle Position (TP) sensor and idle the engine until the MIL comes ON. DTC P0122 should be stored in memory and kept in memory when ignition is turned OFF. If not, the powertrain control module (PCM)/engine control module (ECM) is faulty. When this test is completed, make sure that you clear the DTC from memory.

An intermittent MIL with no stored DTC may be caused by the following:
- Ignition coil shorted to ground and arcing at ignition wires or plugs.
- MIL wire to PCM/ECM shorted to ground.
- Poor PCM/ECM grounds.

Check for an electrical system interference caused by a defective relay, PCM/ECM driven solenoid, or switch. They can caused 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, cellular phones, etc.

Check for open diode across the A/C compressor clutch and check for other open diodes.