Question about GMC Sierra 1500
Hi! The problem could be on the PCM (powertrain control module) itself. The PCM has connectivity on all electrical current that runs inside the car which includes the engine, transmission, accessories, etc. If the capacitor on the PCM is faulty something else fails. A good example will be your defroster. You will need to have the PCM replaced to resolve this. HOpe this helps and thank you for using FixYa!
Posted on Sep 30, 2010
This is caused by a loss of engine vacuum to the dash controller, the vacuum comes from a vacuum reservoir under the hood then a line goes through the dash on the passengers side, make sure u have vacuum at the control head, at least 18 inches,when vacuum is lost to the control the default air flow position is the defrost vents for safety reasons, it is the only vacuum motor that is held on to turn the defrost off, that is to say it is normally open, all the rest of the system vacuum motors are normally closed
Posted on Sep 29, 2010
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Posted on Jan 02, 2017
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