I have a 91 Chev 1 ton dually. Yesterday the instrument brake light came on and started flshing in a distinct pattern (4 short, 1 long flash). The brakes don't feel any different and the pads all have plenty of meat on them. Any idea what the problem is?

Never heard of it happening like that, but it sounds like an ABS code of sorts.


*edit* In my Haynes repair manual for S-10 turcks/blazers, says codes 41 - 66 is a awal module. (4 wheel antilock module)
Check grounds...clear codes. If it comes back, call mechanic. (there words, not mine)

Hi Holytruckster
I see it’s your first post so welcome.

I usually only look at “The 1988-1998 Chevy & GMC Pickups Message Board” at this site. That may have been a better place to post this question.

It sounds like your truck has RWAL. RWAL is not 4 wheel ABS

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.

If the light is blinking the manual states you should still check the codes by turning the key on (engine not running) and put a jumper wire between terminal A and H 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.

This site tells how to read your codes.
http://autorepair.about.com/library/faqs/bl929g.htm

This site has general information about RWAL.
http://www.babcox.com/editorial/tr/tr89850.htm

Generally with this system it is best to: Check the code. Clear the code, and drive the truck and see if the code returns.

Being what you said, when you check the codes it will most likely show a code 5.

Code 5 = Excessive actuations of dump valve during ABS braking

This is not a common code that gets set. The isolation and dump valve are in the same part. It’s located out by the master cylinder.


Welcome again
ChevyTech

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

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.