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 acceptable range.