One problem related to electrical system has been reported for the 1999 GMC Sierra. The most recently reported issues are listed below.
We own a 1999 GMC Sierra pickup. The odometer and shift indicator are the led type. Both the odometer and shift indicator have shorted out and there is no way to tell what the mileage is or what gear the truck is in. This has resulted in two incidents where people were nearly run over because the driver did not know if the truck was in forward or reverse. Also, although the odometer measures mileage, we can't read it because the display is dark. We contacted the dealer about getting this fixed and they indicated the cost was $400 but that they had repaired one of their own vehicles and it shorted out again two times. They just put up with it. To me that says that GMC has a problem with this component and they need to take care of it. This is a safety issue.