Diagnostic Theory

WARNING: This page is about a different car, the 2007 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.