- Preliminary Information

BEFORE USING DIAGNOSIS BY SYMPTOM
Before using this section you should have performed the "Diagnostic Circuit Check" Testing and Inspection and determined that:

^ The control module and Malfunction Indicator Lamp (MIL) (Service Engine Soon) are operating correctly.
^ 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 "Control Module Wiring Diagrams" for application.

SYMPTOM
Verify the customer complaint, and locate the correct symptom in the table of contents. Check the items indicated under that symptom.

^ Always use the Flow Of Diagnosis for proper testing sequence.
^ If the engine cranks but will not start, see "Chart A-3." Related Tests, Information and Procedures

NOTE: It is essential that the vehicle has been properly warmed up and is at operating temperature, except when attempting to diagnose a cold driveability problem. The catalytic converter and feedback system will not function as designed if this is not achieved. Failure to do so will result in inaccurate test results. Verify the correct symptom from the customer.