My 91 gmc pickup has a problem with the brake light on the dash coming on as
soon as the truck reaches 40 mph. If I keep the speed under 40 the light
never comes on.
I checked for codes and there are none. I tested the speed sensor and
it seems fine. Today I replaced the Electronic Brake Control Module with no
luck. Does the speed sensor in the transfer case also control the
speedometer in the dash? My speedo works fine. Does anyone have any idea
what the problem could be?