Road Test and Customer Interview

NVH Diagnosis should always start with the Road Test. Noise, vibration and harshness usually occur in four areas: tires, engine accessories, suspension and driveline. It is important, therefore, that a 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.

NOTE: Information gained from the problem description should never be used in place of facts gained from diagnosis, nor should it be used as an attempted shortcut fix. In the long run, you will save time by adhering to the diagnostic procedures shown.

The Road Test and Customer Interview (if available) provide information that will help identify the condition and will provide direction to the correct starting point for diagnosis.

After reviewing the Customer Interview, the Road Test will provide much of the information that will allow you to identify the condition you are dealing with, directing you to the correct starting point for diagnosis.

1. Make notes throughout the diagnosis routine. It will help cover all the bases when starting to add up the clues. Use a photocopy of the NVH Road Test Form provided. Make sure to write down even the smallest bit of information; it may turn out to be very important.

NOTE: Always use the tachometer in road testing and record engine rpm as well as road speed and road conditions.

2. Perform the Road Test Quick Checks to bring out the problem condition. This will identify the proper section of the diagnosis procedure. Run through the check procedure more than once to be sure you are getting a usable result.

NOTE: The Road Test Quick Checks may not always tell where the problem is, but they will often eliminate other unnecessary checking for you.

3. Do not adjust or repair anything until a Road Test and a thorough visual inspection of the vehicle have been performed. Leave the tire pressures and vehicle load just where they were when the customer brought the vehicle in.

Adjusting the pressures, vehicle load, or making some other seemingly innocent adjustment may reduce the item's intensity to a point where it cannot be identified clearly; it may also inject something new into the system that the customer was not even aware of, preventing proper diagnosis. Make a visual inspection as part of the preliminary diagnosis routine, writing down anything that does not look right. Note tire pressures, but do not adjust them yet. Note leaking fluids, loose nuts and/or bolts, or bright spots where components may be rubbing against each other. Check the luggage compartment area for unusual loads or damage.