Vehicle: 91 chevy sportside, 2x4, 350 engine.

Prob: When I got the truck, the brake light would come on and stay on when the truck was turned on. I have replaced brake Calipers, wheel cylinders, lines, pads and hardware. initially, the light turned of for a while but it has come back on and i cannot figure out why. I have not replaced the master cylinder or the power booster, can either of these be the problem and if so what should I look for.

 

Is the emergency brake up all the way?
Pull up on it and see if light goes out.
Was the switch at the master cylinder replaced?
Try unplugging it and see if light goes out.

 

those models of chevy's are notorius for the brake light switch to go bad...i have replaced 3 on 3 different trucks...a 1989, 1991, and a 1992...it is located under the dash on the brake pedal...very easy to replace...it's probably a dealer item only though...i had to go to the dealer to get mine...hope it helps.....kenny

 

4x4guru he's not talking about the brake lights.
He's talking about the idiot light in the dash.

 

Either hydraulic failure in the system or the parking brake being on will set on the light.

Some Chevy trucks of this vintage have bad proportion valves which can stick leaving the light on. Try depressing on the button on the valve (it's a brass block in the engine compartment) to see if that helps.

 

My 1990 van brake light stayed on later it began flashing a code and would not stay out. I checked the brake system and could find no problems. braking was fine even when pulling a large trailer. I dissconected the battery then reconected it. light when out and has stayed out. possibly something might have stuck and set the code. Im not concerned as all seems to work fine.