How to Use The Diagnostic Procedure

- Noise, vibration and harshness concerns have become more important as vehicles have become more sensitive to these vibrations.
- The diagnostic procedures are provided based on symptom. If the condition occurs at high speed, for instance, the most likely place to start is under High Speed Shake.
- The road test procedure will tell how to sort out the conditions into categories and how to tell a vibration from a shake.
- A series of Road Test Quick Checks is provided to make sure that a cause is either pinpointed or eliminated.
- Name the condition, proceed to the appropriate system and locate the correct diagnosis. When the condition is identified, the job is partly done.
- Follow the diagnostic procedure as outlined.
- Quick Checks are described within the step, while more involved tests and adjustments are outlined in General Procedures.
- Always follow each step exactly and make notes to recall important findings later.

Customer Interview
The road test and customer interview (if available) provide information that will help identify the concern and will provide direction to the correct starting point or diagnosis.

Identify the Condition
Noise, Vibration And Harshness (NVH) usually occur in
four areas:
- Tires
- Engine accessories
- Suspension
- Driveline

It is important, therefore, that an NVH concern be isolated into its specific areas as soon as possible. The easiest and quickest way to do this is to perform the Road Test as outlined.