Measure the battery voltage with an inexpensive digital voltmeter while the problem is occurring. It must be between 13.75 and 14.75 volts. If it is low, all of the things run by the huge number of unreliable computers will not act normally. Suspect the generator. There is no nice way to say it; GM went from the second best generator to the world's worst pile ever starting with the '87 models, and they have no plans on improving this disaster. It is real common to go through four to six of them in the life of the vehicle. What many professionals have been finding out is to reduce the number of repeat failures you must replace the perfectly good battery at the same time. As they age, they lose their ability to dampen and absorb the huge voltage spikes these generators develop due to their design. Those spikes interfere with sensor signals which makes computers do weird things, and they can destroy the diodes and voltage regulator built into the generator, hence the repeat failures. The old battery may work fine yet in an older car.
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Sunday, June 26th, 2011 AT 8:28 PM