check circuit continuity, resistance, and But when computer systems • Close the door.
signals without looking anywhere else. appeared, basic logic took a back seat. • Start the engine.
Bidirectional control systems have In some cases, it may even be a liabil- That’s it. The transmission worked
forced technicians to bid farewell to ity. normally again.
the breakout box. Oh, sure, you can Think that’s an overstatement? Why did it work? Obviously GM’s
still verify a sensor or circuit by going Here’s a real world example, called in engineers built a reset of some sort into
directly to the sensor, and checking the by an ATRA Member, where logic flew the computer system.
continuity to ground or the computer. out the window: Could you have found it using
But since the computers all use The customer came in with a 2007 logic? Not a chance. A thousand mon-
shared data, there’s no one junction for Chevy K2500 equipped with a 6L90E keys typing on a thousand typewriters
measuring every computer sensor or transmission. The technician scanned for a thousand years would never stum-
solenoid. Suddenly you have to know the computer, recorded the codes, and ble upon that specific series of steps.
where to look, and what you’re look- then cleared the codes from memory. The only way to find these fixes
ing for. His next step was to drive the truck to is by getting it from an information
More difficult, sure… but not see if the codes returned. resource such as ATRA. That’s the
impossible. You just have to understand He started the engine, put the trans- great benefit of the ATRA HotLine…
the systems, and take a more hands-on mission in gear, and… nothing. No we put the experience of thousands of
approach to diagnosis. movement in either direction. The pick- technicians from all around the world
up drove in and now it wouldn’t move. right at your fingertips. We unearth
Logical Diagnostic
All he did was clear the codes! these odd corrections and publish them
Procedures: Fortunately the technician had a in GEARS or provide them through the
Good Luck with That!
friend at the local GM dealership. They ATRA HotLine.
had a secret letter from GM, describing Bidirectional computer systems are
Once upon a time, diagnosis was this very condition and telling them the future of vehicle control systems.
about logic: You analyzed the problem what to do: But you can still diagnose those cars if
based on the system operation, and you • Put the transmission in park. you understand how their differences
could logically eliminate systems and • Turn the key off. affect your diagnostic strategy, and use
circuits until you figured out the likely • Open the driver’s door and leave it the proper diagnostic techniques.
2010_mem_1-4_island.qxd 1/6/2010 12:26 PM Page 1
cause of the problem. open for 30 seconds.
AUTOMATIC TRANSMISSION
REBUILDERS ASSOCIATION
TECHNICAL RESOURCES great
BUSINESS SUPPORT
reasons
NATIONWIDE WARRANTY
CONSUMER REFERRALS
to join
NETWORKING GROUPS
EVENTS DISCOUNTS
CERTIFICATION
BENEFIT PROVIDERS
Call the Membership Department at 805.604.2000 or email
membership@atra.com, if you have any questions.
www.atra.com | 805.604.2000
The Automatic Transmission Rebuilders Association is
your resource for tech support, business support,
education, networking, and more. Join today by logging
on at
www.atra.com and get connected with your industry!
GEARS January/February 2010 35
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