Symptoms

Important Preliminary Checks Before Starting
Before using this section you should have performed the Powertrain On-Board Diagnostic (OBD) System Check and determined that the following items are OK:
- The PCM and MIL (Check Engine) are operating correctly.
- There are no DTC(s) stored.
- Scan tool data is within normal operating range, refer to Engine Scan Tool Data List.
Verify the customer complaint, and locate the correct symptom in the table of contents. Check the items indicated under that symptom.

Visual/Physical Check
Several of the symptom procedures call for a careful Visual/Physical Check. The importance of this step cannot be stressed too strongly - it can lead to correcting a problem without further checks and can save valuable time. This check should include:
- PCM grounds for being clean, tight, and in their proper location.
- Vacuum hoses for splits, kinks, and proper connections, as shown on Vehicle Emission Control Information label. Check thoroughly for any type of leak or restriction.
- Air leaks at throttle body mounting area and intake manifold sealing surfaces.
Wiring for proper connections, pinches and cuts.

Intermittents

Important: Problem may or may not turn ON the Malfunction Indicator Lamp (MIL) or store a DTC. DO NOT use the Diagnostic Trouble Code (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 careful visual/physical check. 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.
The vehicle may be driven with a J 39200 Digital Multimeter connected to a suspected circuit. An abnormal voltage when 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. The scan tool has several features that can be used to locate an intermittent condition. 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.
Using a scan tools Freeze Frame buffer can also 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 TP sensor and idle engine until the MIL (Check Engine) comes ON. DTC P0122 should be stored and kept in memory when ignition is turned OFF. If not the PCM is faulty. When this test is completed, make sure that you clear the DTC P0122 from memory.
An intermittent MIL (Check Engine) with no stored DTC may be caused by the following:
- Ignition coil shorted to ground and arcing at ignition wires or plugs.
- MIL (Check Engine) wire to PCM shorted to ground.
- Poor PCM grounds, go to PCM wiring diagrams.
If the intermittent condition exists as a start and then stall, check for DTC(s) relating to the vehicle theft deterrent system.
Check for an electrical system interference caused by a defective relay, PCM driven solenoid, or switch. They can cause 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.
All Ignition Control Module (ICM) wiring should kept away from the generator. Check all wires from the PCM to the ignition control module for poor connections.
Check for open diode across A/C compressor clutch and check for other open diodes, Go to wiring diagrams in Electrical Diagnosis.