Important Preliminary Checks Before Starting
Perform the
Powertrain On Board Diagnostic (OBD) System Check
and verify all of the following before using
the symptom tables:
| • | The powertrain control module (PCM) and the malfunction indicator
lamp (MIL) are operating correctly. |
| • | Check that there are no DTCs stored. |
| • | The scan tool data is within a 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
of 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:
| • | Verify all PCM ground connections are secure, clean, and in the
proper locations. |
| • | 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. |
| • | Verify the mass air flow (MAF) sensor installation is correct. |
| • | Inspect the air inlet ducts for collapsed or restricted sections. |
| • | Check for air leaks at the throttle body mounting area, the MAF
sensor, and the intake manifold sealing surfaces. |
| • | Inspect the ignition coil boots for cracking, hardening, carbon
tracking, and the proper routing to each cylinder. |
| • | Inspect the wiring harness for proper connections and for damage. |
For more symptom base diagnostics refer to the following tables:
