Diagnostic Theory

WARNING: This page is about a different car, the 2010 Mercury Milan, 2010 Lincoln MKZ, and 2010 Ford Fusion. 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 source.
using a systematic method that divides the system into related areas:

The diagnosis and correction of NVH symptoms requires:

a rod or system test to determine the exact nature of the symptom.
an analysis of the possible causes.
testing to verify the cause.
repairing any symptoms found.
a road test or system test to make sure the cause has been corrected or brought back to within an acceptable range.