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pcm resets when i turn car off

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05grandprix05

New member
ok so I have a 2005 grandprix the car needs to pass emissions but there is a problem every time I turn the car off the pcm resets
and I have to start the drive cycle all over again.
I have never had any problems with this car until now any help will be greatly appreciated thanks.
 


You have to go for a long drive for the monitors to run their cycle. I had to wait for 2 days, which is about 120 km (50ish miles).
 
I understand that i ran the car until all monitors were ready. Once everything was ready i took the car to emissions then they turn the car off and back on all the monitors reset meaning they were not ready.
 
you have a scanner or t app to show you that they were ready? and then they reset afterwards?

those things take a long ass time to all become "ready", hell my evap just took 3 weeks. and its codes are deleted lol


t app readiness scanner thing. this dont happen in one drive.

codesshowready_zps806f581d.jpg
 
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yes I have a snap on scanner I drive the car around 65 miles until they all become ready the only one that takes longer is the evap but here in Arizona you can have one not ready
anyways when I turn the car off after a drive and turn it back on the car acts like if you disconnected the battery by resetting the pcm

I unplugged a sensor to get the check engine light on and once I turn the car off the check engine light gets reset
 


Thanks scotty for those diagrams i got a friend of mine to help me out and the pcm was not loosing power. So we decided the problem was the pcm. Bought a new pcm from the dealer and got it reprogramed and that fixed the problem. Passed emissions without a problem now.
 
I bet a reflash of the old PCM would have fixed the issue.

It's not that the computer was even bad really, it still ran the car and performed just fine from the looks of it. Just that it didnt remember certain things. A updated relash likely would have fixed any problems.
 
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