Famous 1999 Gmc Sierra Check Engine Light Is On References. The gas cap is one of the most common causes of a check engine light. Web no matter what is causing the check engine light on your gmc sierra, it’s important to take action as soon as possible.
This turned out to be the passenger side emissions control check valve. This helps the ecm (car’s computer) to know how efficiently the fuel burns during combustion. Web 1 answer centrion answered 13 years ago check your cigarette lighter fuse ( under the hood on the driver's side marked cigar) if that is burned out the communication port won't work.
