Noise, Vibration And Harshness (Nvh); Diagnostic Theory; Know The System; Diagnostic Charts - Ford 2002 Bantam Workshop Manual

100-04-35

DESCRIPTION AND OPERATION

Noise, Vibration and Harshness (NVH)

Noise, vibration and harshness (NVH) is
becoming more important as vehicles become
more sophisticated and passenger comfort levels
increase. This section is designed to aid in the
diagnosis and testing and repair of NVH
concerns.
• Noise is defined as sounds not associated
with the operation of passenger compartment
equipment that interface with customer
satisfaction.
• Vibration is defined as impulses felt by the
customers that are not caused by road
surface changes.
• Harshness is a ride quality issue where the
customer feels that the vehicle response to
the road surface is sharply transmitted to the
customer.

Diagnostic Theory

Diagnosis is more than just following a series of
interrelated steps in order to find the solution to
the specific condition. It is a way of looking at
systems that are not functioning the way they
should and finding out why. Also it knows how
the system should work and whether it is working
correctly.
There are basic rules for diagnosis. If these rules
are followed, the cause of the condition is usually
found the first time through the system.

Know the System

• Know how the parts go together.
• Know how the system operates as well as its
limits and what happens when the system
goes wrong.
• Sometimes this means checking the system
against one that is known to be working
correctly.

Know the History of the System

A clue in any one of these areas may save time:
• How old or new is the system?
• What kind of treatment has it had?
• Has it been serviced in the past in such a
manner that might relate to the present
condition?
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Noise, Vibration and Harshness
• What is the service history?

Know the History of the Condition

• Did it start suddenly or appear gradually?
• Was it related to some other occurrence such
• Know how the condition made itself known; it
Know the Probability of Certain Conditions
Developing
• Look for the simple rather than the complex.
• For example:
• Know the difference between impossible and
• New parts are just that, new. It does not
Do Not Cure the Symptom and Leave the
Cause
Lowering the pressure in a front tyre may correct
the condition of a vehicle leaning to one side, but
it does not correct the original condition.

Be Positive the Cause is Found

• Double check findings.
• What caused a worn component?
• A loose transmission or engine mount could

Diagnostic Charts

Charts are a simple way of expressing the
relationship between basic logic and a physical
system of components. They help discover the
cause of a condition in the least time. Diagnostic
charts combine many areas of diagnosis into one
visual display:
as a collision or previous part replacement?
may be an important clue to the cause.
- Electrical conditions usually occur at
connections rather than components.
- An engine no-start is more likely to be
caused by a loose wire or small adjustment
rather than a sheared-off camshaft.
improbable. Certain failures in a system can
be improbable but still happen.
mean they are always good functioning parts.
indicate that other mounts are also loose.
100-04-35
06/2001 2002 Bantam