Road Test

NVH diagnosis should always start with the road test. Noise, Vibration and Harshness (NVH) usually occur in four areas: tires, engine accessories, suspension and drivetrain. It is important, therefore, that an NVH concern is isolated into its specific area as soon as possible. The easiest and quickest way to do this is to perform a road test.







The road test and customer interview (if available) provide information needed to identify the condition and give direction to the correct starting point for diagnosis.

1. Make notes throughout diagnosis routine. Use a Road Test form that includes space for comments. Make sure to write down even the smallest bit of information, as it may turn out to be most important.

2. Road test the vehicle and define the condition by reproducing it several times during the road test.

3. Perform the Road Test Quick Checks as soon as the condition is reproduced. This will identify the proper system of the diagnostic procedure. Run through the quick checks, more than once, to make sure they are providing a useable result. Remember, the Road Test Quick Checks may not tell where the concern is, but they will tell where it is not.

4. Do not touch anything until a road test and a thorough visual inspection of the vehicle have been performed. Do not change tire pressure or vehicle load. Adjusting tire pressures, vehicle load, or making other adjustments may reduce the condition's intensity to a point where it cannot be identified clearly. It may also inject something new into the system, preventing proper diagnosis.

Make a visual inspection as part of the preliminary diagnostic 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 cargo area for unusual loads.