Diagnostic Theory

WARNING: This page is about a different car, the 2009 Mercury Grand Marquis and 2009 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.

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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 NVH symptoms requires:

a road 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.