- Checking the Basics

Before using this section you should have performed the DIAGNOSTIC CIRCUIT CHECK which verifies the ECM and "CHECK ENGINE" light are operational, as well as no trouble codes were retrieved.
^ Always use the FLOW OF DIAGNOSIS for proper testing sequence.
^ If the ENGINE CRANKS BUT WILL NOT RUN, use CHART A-3 in DIAGNOSTIC CHARTS/A-CHARTS.
^ Several of the following symptom procedures call for a careful visual/physical check. This step is very important - it can lead to correcting a problem without further checks and can save valuable time. To determine if a particular system or component is used on a specific vehicle, refer to the "ECM/PCM Wiring Diagrams" for application.

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.

CHECK THE FOLLOWING:

^ ECM grounds for being clean, tight, and in their proper location.
^ Vacuum hoses for splits, kinks and proper connections. Check thoroughly for any type of leak or restriction.
^ Air leaks at throttle body mounting area and intake manifold sealing surfaces.
^ Ignition wires for cracking, harness, proper routing, arcing and carbon tracking.
^ Wiring for proper connections, pinches, and cuts.
^ Harnesses (EST, ESC, etc...) for proper routing.
^ The following symptom charts contain groups of possible causes for each symptom and cover several engines. These procedures are not meant to be done in consecutive order. If "Scanner" readings do not indicate a problem, then proceed in a logical order, easiest to check or most the likely cause first. To determine if a particular system or component is used on a specific vehicle, refer to the ECM Wiring Diagrams in ELECTRICAL AND ELECTRONIC DIAGRAMS for application.

If there are no codes but the symptoms are intermittent, refer to BASIC OPERATION - ON BOARD DIAGNOSTICS. This check is under ECM DISPLAYS and checks all components and system parameters.

NOTE: The charts under DIAGNOSTIC CHARTS are driveability and component testing charts. The computer communication/display diagnostic charts are in TESTING PROCEDURES under SELF-DIAGNOSTIC SYSTEM.