In Texas, for the annual state auto inspection, now they check the
computer codes if they see the Engine Check bit set on the computer.
Mine was set but I guess my light was reset or something because I
never saw it on since the time I bought the car used. Anyway, it was
set because the computer says my EGR sensor is low and my EGR tubing is
clogged. I replaced the EGR valve and the tube turned out to be very
clean inside. The repair man said I had to drive through many different
driving conditions and scenarios to be recorded before the error codes
would clear. I have driven very much since but the codes are not
clearing. Does the O2 sensor have to be replaced or something like that
even though I didn't get an error for the O2 sensor? One of the
conditions is that I have to drive when the outside air temperature is
over 70F. Is there maybe an outside air sensor that could be out? What
usually stops the EGR codes from clearing? Is it a problem with the
computers software and is there a software update that fixes the
computers' inability to ever clear the error?
Thanks if you can help, George
You can clear all codes (including history ones) by disconnecting PCM power
supply (or battery for that matter). AFAIK you still wouldn't pass emission
tests as these guys require that self-tests that PCM does have been
completed, and along with clearing error codes you're erasing self-test
results as well. Now, I'm not entirely sure how long it takes for these
tests to complete - you definitely have to do a bit of driving tho. Still,
it must be less than clearing history codes - usually history is cleared
after X ignition cycles with no errors, where X is at least 30 (depends on
the initial error code).
Or is your mechanic referring to completion status of these self-tests?
Here are coupla links that can come in handy:
The mechanic cleared the codes after the work and said the same thing
about having to complete the self test. He puled out a big book and
started reading through the self tests that the car does. There have to
be at least 15 times of the engine warming up from a cold state and
being driving through different conditions like driving so much time
around 30-35 mph, driving at highway speeds for so long, driving in
cold weather, warm weather , with tank at least 3/4 full, and on and
I've been driving quite a bit but I'm not sure if it failed inspection
again because the test didn't finish or it finished and failed the test
again. I guess I need to go back and ask about this. I don't know if
the mechanic can tell if it is finished. Maybe he can only see that the
errors never went away.
Get yourself one of these:
Check first what kind of interface your car uses. Then download free
software from scantool.net and you'll be able to see for yourself any
history error codes, test completion status, and much more.
In case anyone else ever has this similar problem, the EGR valve was
good and the EGR tubing was clear. The clog was in the EGR tubing of
the intake manifold after the EGR valve. After taking off the intake
manifold and cleaning it out the problem codes were cleared.
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