7: Diagnostic Procedure

Qualifying the concern by the particular sensation present can help narrow down the concern. Always use the "symptom" to "system" to "component" to "cause" diagnosis technique. This diagnostic method divides the problem into related areas to correct the customer concern.

• Verify the "symptom".
• Determine which "system(s)" can cause the "symptom".
  • If a vibration concern is vehicle speed-related, the tire and wheel RPM/frequency or driveshaft frequency should be calculated.
  • If a vibration concern is engine speed-related, the engine, engine accessory or engine firing frequencies should be calculated.
• After determining the "system", use the diagnostic tools to identify the worn or damaged "components".
• After identifying the "components", try to find the "cause" of the failure.

Once the concern is narrowed down to a symptom/condition, proceed to NVH Condition and Symptom Categories.