Diagnostic Theory

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.