One problem related to exterior rearview mirror has been reported for the 1999 GMC Sierra. The most recently reported issues are listed below.
The abs system vibrates at a low rate and vehicle will not slow down when applying constant pressure on brakes. There appears to be a 2 to 3 second delay between the time abs takes over and when you have come control over the braking of the vehicle. This time elapse causes you to use other means for avoiding an accident such as veering to the left or right to avoid contact during heavy braking. This problem will also occur if the rear drivetran loses contact with the road surface during light braking. The driver has to always be aware of the possibility of not being able to stop to be able to avoid an accident. The outside mirrors on this vehicle ices up completely during winter highway driving at highway speeds over 45 mph. The time it takes for the mirrors to ice up completely is usually less than 15 minutes from initial start.