I have a '90 GMC Jimmy 6.2l diesel and the brake warning lamp is flashing code 18(open or shorted brake switch circuit) . All wiring seems to be ok. Ive replaced the brake switch and ABS module. Also checked bulk head connector. Im starting to run out of ideas. Any opinions and ideas will be greatly appreciated. Thaks for reading

 

is your truck lifted??

if so how much?

and what size tires you running?

my trucks abs get's all confused, flicks on then off and flashes..

it just thinks your going faster or slower than you are, so it doesnt know what to do.

abs still works, maybe not as good, but it does..

i had mine all checked out.. thats all we could come up with.

 

I assume you mean the ABS light is flashing, and when you say code 18...do you mean code 81?
This code can be set if you have a bad habit of using the brake pedal as a foot rest causing the abs module tothikn the brake signal is shorted to battery. Did you check the wiring at the pump? specifically the purple wire, should have 12volts when the brakes are pressed.