Diagnostic Theory

WARNING: This page is about a different car, the 2004 Ford Ranger. However, it is still accessible from the selected car via links, so may be relevant.

The shortest route to an accurate diagnosis results from:

System knowledge, including comparison with a known good system.
System history, including repair history and usage patterns.
Condition history, especially any relationship to repairs or sudden change.
Knowledge of possible sources.
Using a systematic diagnostic method that divides the system into related areas.

The diagnosis and correction of noise, vibration and harshness concerns requires:

A road or system test to determine the exact nature of the concern.
An analysis of the possible causes.
Testing to verify the cause.
Repairing any concerns found.
A road test or system test to make sure the concern has been corrected or brought back to within an acceptable range.