What does a blinking Brake light on a 88 GMC Sierra mean?

[Doc]

Truck is a 1988 GMC Sierra C1500 Regular cab

 

[don r]

Low brake fluid. Top it up if necessary, but get ready for new brakes. When the brakes wear out, the fluid goes down to take up the slack.

 

[bandit_60]

it means it,s losing its contact part of the time. probably it,s the socket.

 

[Sophie B]

it's a code for a problem in the rear anti-lock system...

you count the number of flashs to determine the code

4,6, and nine are common....