- Intermittent Malfunctions

DEFINITION
Problem may or may not turn "ON" the Malfunction Indicator Lamp (MIL) (Service Engine Soon) or store a Diagnostic Trouble Code (DTC).

DTC CHARTS AND INTERMITTENTS
DO NOT use the DTC charts found in Diagnostic Charts for intermittent problems. The fault must be present to locate the problem.

CAUSES AND CHECKS FOR INTERMITTENTS
Faulty Electrical Connections
Most intermittent problems are caused by faulty electrical connections or wiring. Perform the visual and physical checks as described in Preliminary Checks. Check for:

- Poor mating of the connector halves or a terminal not fully seated in the connector body (backed out).
- Improperly formed or damaged terminal. All connector terminals in the problem circuit should be carefully reformed or replaced to insure proper contact tension.
- Poor terminal to wire connection. This requires removing the terminal from the connector body to check. Also, check underhood electrical center for corrosion. Refer to Preliminary Checks. Testing and Inspection

Using Electrical Diagnostic Equipment
If a visual and physical check does not find the cause of the problem, the vehicle may be driven with a J39200 digital multimeter connected to a suspected circuit. A Tech 1 scanner can also be used to help detect intermittent conditions. An abnormal voltage, or reading, when the problem occurs, indicates the problem may be in that circuit. Using the Tech 1's scanner snapshot feature may help locate in intermittent failure. If the wiring and connectors check OK, and a DTC was stored for a circuit having a sensor, except for DTCs 43, 44, 45, 64, and 65, substitute a known good sensor and recheck.

Checking For Loss Of Diagnostic Code Memory
Loss of diagnostic code memory. To check, disconnect Manifold Absolute Pressure (MAP) and idle engine until the MIL (Service Engine Soon) comes "ON." DTC 43 should be restored, and kept in memory when ignition is turned "OFF." If not, the PCM is faulty.

Intermittent MIL - No Stored DTC
An intermittent MIL (Service Engine Soon) with no stored DTC may be caused by:

- Ignition coil shorted to ground and arcing at ignition wires or plugs.
- MIL (Service Engine Soon) wire to Powertrain Control Module (PCM) shorted to ground.
- Output or field service enable terminal wire to PCM shorted to ground.
- PCM grounds, refer to PCM wiring diagrams.

Start And Then Stall
If the intermittent condition exists as a "start and then stall," check for DTC(s) relating to the theft deterrent systems.

Electrical System Interference
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.

After-Market Equipment
Check for improper installation of electrical options such as lights, cellular phones and other after-market equipment.

Wire Routing
All Ignition Control (IC) wires should be routed away from secondary ignition wires, distributor, coil and generator. All wires from the PCM to distributor should have a good connection.

Open Diode
Check for an open diode across the A/C compressor clutch, and for other open diodes. Refer to Diagrams/Wiring.

Problem Not Found
If problem has not been found, refer to PCM Connector Symptom Charts. PCM Control Module Diagnosis