Important Preliminary Checks

Before Starting
Before proceeding with this troubleshooting you should have performed the On-Board Diagnostic (OBD II) System Check and determined that:
- The powertrain control module (PCM)/engine control module (ECM) and the Malfunction Indicator Lamp (MIL) are operating correctly.
- There are no Diagnostic Trouble Codes (DTCs) stored.
- The scan tool data is within normal operating range.

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/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.

Wiring for proper connections, pinches and cuts.