A problem may or may not turn ON the malfunction indicator lamp (MIL) or store a DTC. 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 faulty electrical connections or wiring. Perform a careful visual/physical check for the following conditions:
| • | Inspect for poor mating of the connector halves or a terminal not fully seated in the connector (backed out). |
| • | Check for improperly formed or damaged terminals. |
| • | Inspect all connector terminals in the problem circuit should be carefully checked for proper contact tension. |
| • | Inspect for a poor terminal to wire connection. This requires removing the terminal from the connector body to check. |
| Refer to Testing for Continuity , Repairing Connector Terminals , and Connector Repairs in Wiring Systems. |
Road test the vehicle with a digital multimeter (DMM) connected to a suspected circuit. An abnormal voltage or amperage reading when the malfunction occurs is a good 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. This stored information then can be reviewed by the service technician to see what caused the malfunction. |
| • | A scan tool 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 be driven within the conditions that were present when the DTC originally set |
Check for a loss of diagnostic code memory. To check, disconnect the MAP sensor and idle engine until the MIL (Service Engine Soon) comes ON. DTC P0107 should be stored and kept in memory when the ignition is turned OFF. If not, the PCM is faulty. When this test is completed, make sure that you clear the DTC P0107 from memory.
An intermittent MIL (Service Engine Soon) with no stored DTC may be caused by the following:
| • | Inspect the ignition coil for a short to ground and arcing at the ignition wires or the spark plugs. |
| • | Check the MIL (Service Engine Soon) wire to the PCM for a short to ground. |
| • | Check for poor PCM grounds. Refer to
IGN Switch, PCM Feeds
. |
Check for improper installation of electrical options such as lights, cellular phones, etc. Route the ignition control (IC) module wiring away from the secondary ignition wires and the ignition coils . Check all wires from the PCM to the ignition control module for poor connections.
Refer to Testing for Continuity , to Repairing Connector Terminals and to Connector Repairs in Wiring Systems.
Check for an open diode across the A/C compressor clutch and check for other open diodes. Refer to Engine Controls Schematics .
