Battery Meter goes down. It even turns off the car. on 2002 GMC Yukon

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Have a 2002 Yukon SLT4WD. When I drive my car by night. The battery meter goes down everytime I brake or release the accelerator pedal and sometime it even turns off the car. I chekced the sparkplugs, the alternator, they're when I drive in D. The lights or the battery goes down. can you help me about it?? (I live in Tahiti
Thank You... William.)
(1) Answer
It sounds like the engine idle may be to low on your Yukon. There could be deposits built up behind the throttle plate which will restrict the air flow at idle. The fix would be to clean the throttle body area with carburetor cleaner and wipe it out with a clean shop rag. There may also be a software update available from GM which will help the computer compensate to the build-up of future deposits in the throttle body. The check engine (SES) light may be on after cleaning the throttle body and the code set will need to be cleared to turn off the light.