Important Preliminary Checks Before Starting
Perform the
Powertrain On Board Diagnostic (OBD) System Check and verify that all of the following are true before using the Symptom Tables:
| • | The PCM and the MIL (Service Engine Soon) are operating correctly. |
| • | Check that there are no DTCs stored. |
| • | 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. |
Several of the symptom procedures call for a Careful Visual/Physical Check. DO NOT neglect to perform the Careful Visual/Physical Check. The Careful Visual/Physical Check is an important procedure that can lead to the correction a concern without further
diagnosis. The performance of the Careful Visual/Physical Check can save valuable time. The Careful Visual/Physical Check should include the following:
| • | Inspect all PCM grounds for secure and clean connections that are in the proper location. |
| • | Check all vacuum hoses for splits, kinks, and proper connections, as shown on the Vehicle Emission Control Information label. Check the vacuum hoses thoroughly for any type of leak or restriction. |
| • | Inspect the air inlet ducts for collapsed or restricted sections. |
| • | Air leaks at throttle body mounting area and intake manifold sealing surfaces. |
| • | Inspect the ignition system secondary wires for cracking, hardening, carbon tracking and the proper routing to each cylinder. |
| • | Inspect the wiring harness for proper connections and damage. |
For more symptom base diagnostics refer to the following tables:
