91 Gmc brake light comes on after 40 mph
Question:
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? Thanks, Mariano
Response:
> 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? > Thanks, Mariano
Try unplugging the proportioning valve sender. It’s a little yellow, single wire plug just below the master cylinder. The prop. valve sender sits in the top of the aluminum prop. valve. Doc – Hide quoted text — Show quoted text –
