Unplug the ABS system from the black box on the side of the master cylinder (I believe it is the bottom plug). Turn the ignition to the on position but don't start the engine. Wait at least 30 sec, then turn off the ignition. Plug the ABS system back in and see if that clears your problem.

 

Tried unhooking it and following the instructions several times...no luck. It seems to flash 8 times then a long flash, then 8 more...????

 

Disconnect the batteries for a few minutes, then reconnect them. My 1990 suburban did the same thing.

 

That did it! Unhooked the battery for a minute and brake light flashing is no more! THANKS! Now, maybe you can solve my 454 engine getting 12 mph on the road!

Eddy

 

12 MPH? Step on the long vertical pedal on the right side of the driver side floorboard.
Now, if 12 MPG is your problem, Either swap down to a 350, or go diesel.

 

What the hell kind of MPG do you expect to get out of a 15 year old BB

Hell brand new ones with a 350 are only getting 15 MPG :flipoff2:

 

After unhooking the battery the flashing brake light went out....for a week. It came on as before, flashing 8 times and stopping, then starting again. I ignored it for a month or so until Monday when the brakes went out- completely. Managed to coast it to the GMC dealer where they replaced the master cylinder. So....I guess the flashing light was a warning after all.

Eddy