Test Notes

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

- The NVH diagnosis road test starts with the customer interview. The service writer must get as much information as possible about the problem and, if possible, take a test drive with the customer, to minimize confusion arising from descriptive language differences. The history of the problem must be investigated: When was it first noticed? Did it appear suddenly or gradually? Did any abnormal occurrence coincide with or precede its appearance (such as pothole or curb impacts, minor collisions, etc.)? Were any service procedures performed or parts replaced? It is also necessary to know any special conditions affecting the appearance and degree of the problem, such as road speed, type of road, drive mode, engine temperature, ambient temperature, etc.

- A gradual appearance of the problem indicates a deterioration of a component, such as tires, front wheel driveshaft joints, an accessory drive belt, or a wheel bearing.

- A sudden appearance of the problem could indicate a lost wheel balance weight, or frozen front wheel driveshaft joints.

- 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 included. Make sure to write down even the smallest bit of information; it may turn out to be very important.
2. Perform the Road Test Quick Checks to bring out the problem condition. This will identify the proper diagnostic technique. Run through the check procedure more than once to be sure you are getting a useable 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.

- Do not touch 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 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 cargo area for unusual loads or damage.