I have a brake light that stays on, started yesterday. The owners manual says to take the truck in, something has failed in the brake sysytem.

Where should I start looking? Any ideas?

 

the obvious answer is to check the parking brake, make sure it is not on...sorry, I know it's obvious but sometimes those are the ones that get ya... Might also make sure the plunger switch on the parking brake is operating...it can get stuck, a little wd40 will free it. If that's not it I'd then check the master cylinder, make sure the fluid level is ok, do a visual inspection around it and the wheels, see if you see any leaks. Pay special attention to the rubber hoses. After that, I'd start thinking master cylinder might be bad-- but there are usually some other symptoms (like a squishy pedal)....any other issues?

 

Are you talking about a warning lamp on your dash, or an actual brake light?