- Important Preliminary Checks
BEFORE USING THIS SECTIONBefore using Diagnosis by Symptom you should have performed the Diagnostic Circuit Check and determined that:
1. The Powertrain Control Module (PCM) and Malfunction Indicator Lamp (MIL) "Service Engine Soon" are operating correctly.
2. There are no diagnostic trouble codes stored, or there is a diagnostic trouble code but no MIL "Service Engine Soon."
SYMPTOM
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 and sensors 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.
^ Ignition wires for cracking, hardness, proper routing and carbon tracking.
^ Wiring for proper connections, pinches and cuts.