How to Use The Diagnostic Procedure

- Noise, vibration and harshness concerns have become more important as vehicles have become more sensitive to these conditions.
- The diagnostic procedures are 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.
- Use Vehicle Road Test Evaluation form.
- Use the Glossary to become familiar with the terms.
- Name the condition, go to the appropriate system and locate the proper diagnosis. When the condition is identified, the job is partly done.
- Follow the diagnostic procedure.
- Quick Checks are described within the step, while more involved tests and adjustments, refer Adjustments.
- Always follow each step exactly and make notes along the way to recall important findings.







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 for diagnosis. Use Customer Concern Evaluation form to record customer concerns.

Identifying 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 area as soon as possible. The easiest and quickest way to do this is to perform a road test. Component Tests and General Diagnostics