I never took the time to test one that way, but yes, they should hold vacuum. If there has not been a related fault code set, the readings can be within the acceptable limits, but wrong. Just find a used sensor in a salvage yard and pop it in to try it. Unlike those from the late '80s that were supplied by GM and had an almost 100 percent failure rate, the newer ones don't fail real often anymore. With one common type of failure, the engine will continue to run, (poorly), as long as the gas pedal is moving.
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Monday, January 9th, 2012 AT 2:32 AM