For 1990-2009 cars

An intermittent condition may or may not store a DTC or illuminate the Malfunction Indicator Lamp (MIL) . DO NOT use the Diagnostic Trouble Code (DTC) charts for intermittent problems. The fault must be present to locate the problem.

Most intermittent problems are caused by loose electrical connections or malfuctioning wiring. Perform a careful visual/physical check for the following conditions:

• | Poor mating of the connector halves or a terminal not fully seated in the connector (backed out).

• | 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.

Road test the vehicle with a J 39200 Digital Multimeter connected to monitor voltage on a suspected circuit. An sudden change in voltage when the malfunction occurs is an indication that there is a fault in the circuit being monitored.

Use a scan tool to help detect intermittent conditions. The scan tool has several features that can be used to locate an intermittent condition. Use the following features to find intermittent faults:

• | The Snapshot feature can be triggered to capture and store engine parameters within the scan tool when the malfunction occurs. The stored information then can be reviewed by the service technician to determine what caused the malfunction.

• | Viewing the Freeze Frame data or Failure Records data can also aid in locating an intermittent condition. Review and record the information in the freeze frame or failure record associated with the intermittent DTC being diagnosed. The vehicle can then be driven within the conditions that were present when the DTC originally set.

Loss of diagnostic code memory. To check, disconnect the MAF sensor and idle engine until a DTC sets . DTC P0102 should be stored and kept in memory when ignition is turned OFF. If DTC P0102 does not remain in memory, the PCM is malfunctioning. When this test is completed, make sure that you clear the DTC P0102 from memory.

An intermittent MIL with no stored DTC may be caused by the following conditions:

• | Ignition system secondary components arcing to wiring harnesses.

• | MIL control circuit wiring intermittently shorted to ground.

• | Poor PCM grounds.

Check for improper installation of electrical options such as lights, cellular phones etc. Ensure that engine harness routing is correct. Check all wiring between the PCM and the ignition control module for poor connections.

Check for open diode across A/C compressor clutch and check for other open diodes. Refer to wiring diagrams in Electrical Diagnosis .