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ChevyTech · 04-24-2010, 08:29 PM

It sounds like the RWAL system is turning the dash brake light on.
RWAL stands for REAR WHEEL ANTILOCK. RWAL was standard equipment starting in 1988 on full size trucks.

1988 and newer trucks of that body style that do not have 4 wheel ABS have RWAL.

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

Watch the light very closely and apply the parking brake. Did the light get brighter?

When the key is first turned on the RWAL module turns the dash brake indicator light on for 2 seconds, then it should go off.

You can unplug the wire on the Combination valve to see if it is the cause on the light coming on.

The RWAL system can store trouble codes, but it is only capable of storing one code at a time.

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. Count the brake light flashes.

You can retrieve RWAL codes without a scan tool.

If the instrument panel light is on, 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. Checking for a code when no code is present sets a code 9, WHICH WILL DISABLE THE RWAL system.

Clearing codes
You can clear the code by removing the power to the RWAL module for 10 seconds. Multiple circuits send power to the RWAL module and the fuses may be labeled STOP/hazard and BRAKE. Removing a fuse labeled RWAL may not clear the code. GM information on which fuse/fuses to pull is not very reliable.

The 1993 manual states to remove the STOP/HAZARD fuse.

Let me know what code or if you find a code.

04-24-2010, 08:29 PM	#2
ChevyTech Registered User Join Date: May 2004 Location: Minnesota Posts: 4,620	Re: Brake light on. Codes? It sounds like the RWAL system is turning the dash brake light on. RWAL stands for REAR WHEEL ANTILOCK. RWAL was standard equipment starting in 1988 on full size trucks. 1988 and newer trucks of that body style that do not have 4 wheel ABS have RWAL. 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 Watch the light very closely and apply the parking brake. Did the light get brighter? When the key is first turned on the RWAL module turns the dash brake indicator light on for 2 seconds, then it should go off. You can unplug the wire on the Combination valve to see if it is the cause on the light coming on. The RWAL system can store trouble codes, but it is only capable of storing one code at a time. 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. Count the brake light flashes. You can retrieve RWAL codes without a scan tool. If the instrument panel light is on, 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. Checking for a code when no code is present sets a code 9, WHICH WILL DISABLE THE RWAL system. Clearing codes You can clear the code by removing the power to the RWAL module for 10 seconds. Multiple circuits send power to the RWAL module and the fuses may be labeled STOP/hazard and BRAKE. Removing a fuse labeled RWAL may not clear the code. GM information on which fuse/fuses to pull is not very reliable. The 1993 manual states to remove the STOP/HAZARD fuse. Let me know what code or if you find a code. __________________ For those of you that are wondering why you are not getting replies to your thread: Did you give the model, year, engine, fuel system type, and transmission information? If it is modified from what came stock from the factory, let us know that too.