On Thu, 17 Dec 2015 13:30:22 -0500, "Ralph Mowery"
wrote:
Always start with the most expensive part. If it is not bad, it will be
when it is ripped out.
Never do anything that can't be undone.
I had a Toyota that started running vrey bad with about 130,000 miles on it.
I repalaced the simple things like the plugs, wires, coil and fuel filter.
Nothing helped. From there a Autozone trouble shooting chart indicated a
sensor that was about $ 500. I took it to the local Toyota dealer and let
them look at the problem as I did not want to spend $ 500 and not need that
part. They kept it about 3 weeks and changed a few other parts including
the spark plug wires as I did not use Toyota wire. Finally they changed
that $ 500 sensor and it ran like it should. I would have thought a dealer
could run some tests but seems like they were just parts changers. Really
ticked me off as they had put on about $ 150 worth of parts that were not
needed and still charged me for them not counting on the 3 weeks it took
them.
I had almost the same situation, except it was the rear oxygen sensor.
The dealer wanted to replace the very expensive catalytic converter.
The dealers computer diagnostics all pointed to the catalytic
converter. They even called the factory service support number, which
confirmed that the diagnostics conclusively pointed to the catalytic
converter. However, I was able to listen to this conversation and
detected considerable uncertainty and lack of competence on everyones
part. Something seemed wrong, so I decided to do some checking. The
internet was full of the usual mix of wisdom and useless garbage, but
I did manage to find an article suggesting that the rear oxygen sensor
tends to get contaminated by various exhaust products, and that since
it's two orders of magnitude cheaper than a catalytic converter, it
should be replaced first. I replaced it, and all as well.
I was curious as to what had just happened, so I went back to the
dealer, told them the story, and asked a few questions. Basically,
there is nobody in the system that knows how to troubleshoot a vehicle
without totally relying on the computerized hardware. The programming
is not intended to nail down the exact cause of a problem, only the
most probable causes, expecting the dealer to replace things in a
rational and logical order based on their experience. In other words,
the computer supplies a shopping list that usually includes a large
number of irrelevant replacement parts and procedures. When calling
factory service support, they don't have experienced techs on the
phones. They just read the computer screen. I was also told that it
was amazing that the diagnostics programs worked because the factory
was constantly making changes and improvements that affected
recommendations.
In my distant past, I had the displeasure of integrating BITE (built
in test equipment) in some radios. The test system caused more
failures than it detected. The diagnostics could be easily mislead,
producing insane results. Even worse, it could not diagnose itself.
All I can say is that such diagnostics are NOT easy to do, especially
with a moving target, such as an automobile.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558