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Bob
Bob, Auto Tech
Category: Chevy
Satisfied Customers: 4087
Experience:  Plus 40 years GM, over 30 certified with Chevrolet, ASE certified Master Tech. (Expired, Retired)
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1996 Chevy Cavalier: suddenly lost power, it is showing codes PO172

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I have a 1996 Chevy Cavalier that suddenly lost power, it is showing codes PO172, and PO325. What could be the cause of this sudden loss of power?
HiCustomer Oh boy, this one is not going to be easy. Your code P0172 (Fuel Trim Rich) could be caused by, a bad PCM (power train control module) Restricted exhaust system a bad fuel injector or any of a few more reasons. Your code P0325 relates to the knock sensor, which could also be caused by a bad PCM, a problem with an injector or injector coil, a throttle position sensor or a Map sensor. There is really not much here that can be tested at home with a volt meter or a test light. About the only thing you could check for yourself would be for a restricted exhaust system, something like a plugged Cat Converter. It would not be that hard to drop the exhaust system and see how much difference in performance it makes. But the best and only sure way to find the problem is going to be with the use of a class 2 scan tool like the dealers use that is capable of running performance and function tests and has the ability to do freeze frame testing. With the scanner the components can be tested to see which ones fall out of perimeter tolerances and which ones do not. The tester can actually be set to freeze frame and record all of the pertinent information related to when the failure occurs and under what conditions. If you have access to this type of scanner, I can send you a long list of diagnostic checks and the check list flow sheet from GM. If you do not, as much as I hate to suggest it a trip to the dealer may be in order. It would be real e-z to spend a lot of money throwing parts at it with the hope of fixing it, to only find out that you had just wasted money on yet another part that it didn't need or that didn't fix the problem. With these kinds of codes, it is even possible for one component to set both codes or for one code to cause the other. the first step at the dealership would be to clear all the codes, then hook up the scanner and take the car for a drive to see which ones reset and in what order and at what speeds and under what conditions, The fix will be the e-z part. Actually diagnosing and finding the guilty culprit in the way of failed components is where the work is going to come in and without the tool it will be nearly impossible. I really am sorry that I can't give you an answer that you would like to hear, but anything else I said would be a waste of your time and mine. Thanks, Bob
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