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Expert
79 Answers
- Posted on Jan 10, 2010
Re: A p1639 code on a 03 pontiac grand am
That code is the 5 volt reference circuit for the a/c pressure sensor and the fuel tank pressure sensor. Disconnect either sensor, one at a time and check for 5 volts at each end to see which end it is having the problem on. Sometimes you can reset the code and it will never come back on again.
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