Page 6 - AAA Northwest Ohio - AAA Now! January/February 2013
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january/february 2013
automotive
services
W
hen your auto repair shop recommends a
‘computer diagnosis’ it sounds serious, and
everyone knows that serious vehicle problems can
lead to serious repair bills. However, AAA experts
advise consumers not to be overly concerned
because computer diagnosis is a common practice
for identifying problems on today’s microprocessor-
controlled cars.
“If your vehicle needs a computer diagnosis, don’t
be alarmed. This is often the most efficient and
cost effective way for an automotive technician to
diagnose a problem,” says John Nielsen, director,
AAA Automotive Engineering and Repair. “Just be
sure to have the repair facility explain what will
be done before you authorize the work because
‘computer diagnosis’ is a generic term that can
cover a wide range of operations.”
To help motorists better understand computer
diagnosis, AAA Automotive Engineering offers the
following information. Based at the association’s
national office in Heathrow, FL., the automotive
engineering team’s goal is to provide motorists with
unbiased information and advice on automotive
technology.
Modern vehicle electronic control systems “know”
and monitor the operating parameters of every
component. When
the Powertrain
Control Module (PCM)
that manages the
system sees a signal
that is outside normal
limits, or fails to see
an expected change
in a signal, it stores
a Diagnostic Trouble
Code (DTC).
To access DTCs,
technicians connect
a “scan” tool to a
Diagnostic Link Connector that is commonly
located under the driver’s side of the instrument
panel. The scan tool displays any stored codes,
but that is only the beginning of a full computer
diagnosis.
DTCs don’t tell a technician if a particular part
is bad, they only indicate that the PCM has seen
something it didn’t expect in a certain circuit. The
problemmight be the part, but it could just as
easily be an issue with the circuit’s electrical wiring.
Sometimes, DTCs are set when there is nothing
wrong with the electronic control system. This
happens when a mechanical problem, like an
engine vacuum leak, creates operating conditions
that cause system components to generate signals
outside their normal range.
To pinpoint a problem, the technician starts with
the DTC, then performs additional tests. These
can range from mechanical checks, like engine
compression, to in-depth electronic diagnosis. One
common procedure uses special test equipment to
access the electronic control system data network
and monitor real-time signals from the system
components.
The ability of technicians to determine what
additional tests are needed, and to accurately
interpret both test results and computer network
data, comes from extensive training and experience.
Today’s technicians use vehicle computer diagnosis
in much the same way surgeons employ medical
testing. In both cases, combining test results with
expert knowledge and skilled hands can lead to an
accurate diagnosis and an ultimate cure.
If you don’t have a good relationship with an auto
repair shop you can trust to properly diagnose your
car’s problems, consider using one of the three area
AAA Car Care Plus Maintenance and Repair shops in
northwest Ohio. Are you more of a do-it-yourselfer?
Visit
to search for
issues you are seeing with your vehicle. Then visit
for videos and tutorials on more
DIY car projects from maintaining your vehicle
appearance to prolonging the life of your engine.
As always, visit
to schedule an
appointment if your project did not turn out quite
as planned.
Automobile Computer
Diagnosis
AAA Experts Explain How Repair Shops
Find Problems
Vehicle computer diagnosis combines test results with expert
knowledge to help “cure” what ails your automobile
Winter is here.
Are your tires ready?
The tires on your car should be
checked to make certain that there
is enough tread on them to get you
through the ice and snow. How
do you check? Each tire has wear
bars running across the tire. When
the wear bar can be felt or is even
with the tread, the tire needs to be
replaced. At this point the tires are
considered legally bald with 2/32 of
tread remaining. If you are unsure,
you can use a penny to check the
tread on your tires. Place the penny
in the tread area with Lincoln’s head pointing
down. If you can see Lincoln’s head the tire has
2/32 of tread and should be replaced.
Your tire pressure should be checked on a
regular basis. Tire pressures will drop in the
winter as a result of the cold temperatures.
The vehicle manufacturer’s recommended tire
pressures can be found on the driver’s door
jamb, these are the pressures you should use
when adding air to tires. If you are not sure visit
a AAA Car Care Plus repair facility and we will
gladly check them for you.
Do your tires pass the test? If new ones are
needed, visit AAA Car Care Plus for all your tire
needs. We now carry and stock Cooper, Pirelli
and Yokohama tires. We offer competitive
prices and would be happy to give you a quote.
Stop in today and we will check your tire tread
and pressure and prepare you for winter.
Tires
101
