- Intermittent Malfunctions

INTERMITTENTS
Definition: Problem may or may not turn "ON" the Malfunction Indicator Lamp (MIL) or store a Diagnostic Trouble Code (DTC).

IMPORTANT PRELIMINARY CHECKS
Before using this section you should have performed the "On-Board Diagnostic System Check" - Powertrain/On-Board Diagnostic System Check and determined that:
1. The control module and MIL (Service Engine Soon) are operating correctly.
2. There are no diagnostic trouble codes stored, or there is a diagnostic code but no MIL (Service Engine Soon).
^ Several of the following symptom procedures call for a careful visual/physical check. The importance of visual/physical checks cannot be over stressed. because they can lead to correcting a problem without further checks and can save valuable time.

VISUAL / PHYSICAL CHECK
This check should include:
^ Control module 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 all mounting areas of the intake manifold sealing surfaces.
^ Ignition wires for cracking, hardness, proper routing, or carbon tracking.
^ Wiring for proper connections, pinches, and cuts.
^ The following symptom charts contain groups of possible causes for each symptom and cover several engines. These procedures are not necessarily meant to be done in consecutive order. If Tech 1 scan tool readings do not indicate the problems, then proceed in a logical order, easiest to check or most likely cause first. To determine if a particular system or component is used on a specific vehicle, refer to the "Electronic/Powertrain Control Module (ECM/PCM)" Wiring Diagrams for application. Electronic/Powertrain Control Module (ECM/PCM)

^ DO NOT use the Diagnostic Trouble Code (DTC) charts in for intermittent problems. The fault must be present to locate the problem. If a fault is intermittent, use of diagnostic trouble code charts may result in replacement of good parts.

FAULTY ELECTRICAL CONNECTIONS OR WIRING
* Most intermittent problems are caused by faulty electrical connections or wiring. Perform careful check of suspect circuits for:
- Poor mating of the connector halves, or terminals, not fully seated in the connector body (backed out).
- Improperly formed or damaged terminals. All connector terminals in 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.

ROAD TEST
* If a visual/physical check does not locate the cause of the problem, the vehicle can be driven with J 39200 voltmeter connected to a suspected circuit or a Tech 1 scan tool may be used. An abnormal voltage or scan reading, when the problem occurs, indicates the problem may be in that circuit. If the wiring and connectors check OK, and a diagnostic trouble code was stored for a circuit having a sensor, except for DTCs 44 and 45, replace the sensor.

INTERMITTENT "MALFUNCTION INDICATOR LAMP (MIL)"
* An intermittent MIL and No Diagnostic Trouble Codes (DTCs), may be caused by:
- Electrical system interference caused by a defective relay, control module driven solenoid, or switch They can cause a sharp electrical surge. Normally, the problem will occur when the faulty component is operated
- Improper installation of electrical devices, such as lights, 2-way radios, electric motors, etc. Ignition Control (IC) wires should be routed away from spark plug wires, ignition system components and generator. Wire for CKT 453 from control module to ignition system should be a good ground
- Ignition secondary shorted to ground
- CKT 419 Malfunction Indicator Lamp (MIL) or CKT 451 (diagnostic "test" terminal) intermittently shorted to ground
- Control module grounds.

LOSS OF DIAGNOSTIC TROUBLE CODE MEMORY
* To check, disconnect Throttle Position (TP) sensor and idle engine until the "Malfunction Indicator Lamp" comes "ON" DTC 22 should be stored, and kept in memory when the ignition is turned "OFF" for at least 10 seconds If not, the control module is faulty.