Inspection and Verification (Start Testing Here)

This is designed to give a working knowledge of the process of diagnosing Noise, Vibrations, And Harshness (NVH) situations. The topics are discussed based on the description of the condition.
- If the condition occurs at high speed, the most likely place to start is under High Speed Shake in the Symptom Chart.
- The Road Test section will tell how to sort the conditions into categories and how to distinguish a vibration from a shake. It will give hints on quick checks to make sure that a cause is either pinpointed or eliminated.

How to Use These Diagnostic Procedures
Become familiar with the terms. Use the Glossary of Terms to find the descriptive name of conditions not encountered before. After naming it, proceed to identifying the condition and locate the proper diagnosis. Remember, by beginning at that point, most other systems in the vehicle have been eliminated; when the proper test is identified, the job is partly done. Follow the steps within the test. Quick Checks are described within the step, while more involved tests and adjustments are found in Service and Repair and Adjustments. Always follow each step exactly and make notes along the way to recall important findings later.

Customer Interview
It is important to interview the customer. Customer feedback can supply information that could be helpful in diagnosing the concern. Ask questions like:
- When is the concern present (at idle or while driving)?
- Where does the concern appear to be coming from?
- How long has the concern been there? Has it steadily become worse?
- When did the concern start?
- Does it change with engine speed or with vehicle speed?