Diagnostic_Process_Guide - 7

Creating a worksheet like this one will help technicians document the results of their tests and provide you and the
customer with information that can help in explaining what is " good " and " bad " with the vehicle.

and needed another one. Being as this
technician was right much more than he
was wrong, we ordered another sensor.
When the new sensor came, he installed
it then came to me saying the car needed
a new powertrain control module (PCM).
This is where I stopped him. We have
replaced very few computers because we
have found computers to be extremely
reliable and, in most cases, issues are
caused by other factors. I followed the
technician to the car where I was going
to confirm the need of the PCM. As I was
walking by the rear of the car, I noticed
a " popping " sound coming from the
exhaust. I asked the technician if he had
checked engine vacuum with a vacuum
gauge. He said he hadn't and just assumed
it was okay. We installed a vacuum gauge
on the manifold and saw that the vacuum
was jumping between 15 to 25 inches of
vacuum, indicating a broken valve spring.
A MAP sensor reads engine vacuum
and reports it to the PCM. Since the vacuum reading was fluctuating so much, the
computer assumed the sensor was faulty
and set a code.

As soon as I returned to my office, I
sat down and wrote a complete diagnostic process, which included duplicating
the customer's concern and checking
the basics like engine vacuum and battery voltage.
I have since evolved our diagnostic
strategy to include a three-stage process.
Stage one is a system check, including the basics. Stage two is a little more
involved with performing some intrusive
tests when necessary, such as compression testing or timing belt alignment. If
the diagnosis is not clear after stage one
and two, a stage three is required where
you would perform specific pier to pier
or pinpoint tests from the computer to
individual components.
By using this approach, we have
found it much easier to set a price and
explain to the customer what we are doing
and provide the results of a diagnostic
test to them. Another good reason for
a detailed process is that every technician can be trained to perform the process so that every vehicle is tested in the
same manner.

These examples help to explain why a
diagnostic process is necessary. In order to
implement this process in your shop, first
meet with your technicians and ask them
how they approach a diagnostic problem.
Document these steps, then meet again
with your technicians to make sure they
are on board with the new, formal process. Once your shop's technicians are
on board, create a worksheet that must
be completed as they diagnose vehicles.
Documenting the results of their tests
will provide you and the customer with
information that can be useful in not only
diagnosing the issue, but it will help in
explaining what is " good " and " bad " with
the vehicle.
The good and bad can assist you in
charging a reasonable fee for your diagnosis, and quite possibly help you sell
additional services.
Understanding why you need to
develop a process, and following through
with implementing it with your technicians, will pay dividends almost immediately by improving the quality of your
diagnostic test procedures.

December 2020 I Diagnostic Process I 7

Diagnostic_Process_Guide

Table of Contents for the Digital Edition of Diagnostic_Process_Guide