brake light on dash. wont go out.

[Slatherd]

A few years back, I went through a snow bank. Ever since then, I cant get my brake light on my dash do go out. When I push my emergency brake, it gets brighter. When I release it, it goes dimmer.

It's really distracting when night driving. It used to blink which was worse. Now it just stays on.

[ChevyTech]

I am assuming this is on your 1991 GMC. It sounds to me like you have a truck with RWAL. RWAL stands for REAR WHEEL ANTILOCK.

There are three brightness levels of the dash brake indicator light on RWAL equipped trucks.

Brightest – park brake
Medium – Combination valve (aka metering & proportioning valve)
Dim – RWAL System

This system can store trouble codes. You can retrieve RWAL codes without a scan tool.

To retrieve RWAL codes connect a jumper wire between terminal H and terminal A of the ALDL connector with the key on (engine not running). Watch the dash brake lamp and count the blinks. Sometimes RWAL system send out a phantom blink before the code blinks start. It can take up to 20 seconds for the code to start coming out.

Checking the code with this method can set a false code 9.

If you get one long flash and 5 shorter flashes that is a code 6.

The RWAL system is only capable of storing one code at a time.

You can clear the code by removing the fuse for 10 seconds then reinstalling it. The fuse should be labeled STOP or BRAKE.

It is possible to set a trouble code without having a failed part. Something as simple as spinning the tires in the snow can set an erratic speed code.

If it were my truck I would read the code, then clear the code, and drive the truck and see if the code comes back again.

Here are some sites that have some RWAL info:
http://autorepair.about.com/library/faqs/bl929g.htm

http://www.babcox.com/editorial/tr/tr89850.htm

ChevyTech