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Username Post: Brake light flashing        (Topic#155724)
Iceline 
Member
Posts: 65

Loc: Buffalo NY
Reg: 12-17-04
03-31-07 08:03 AM - Post#1132457    

My brake light started flashing this week. It flash's with 3 short lights and one longer light. I am assuming this is a code. Any help would be appriciated.


 
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Chevytech 
Subject Matter Expert - Senior Member
Posts: 3014

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
03-31-07 03:04 PM - Post#1132665    
    In response to Iceline

WHAT YEAR IS THE TRUCK???????????

Sounds like it has RWAL

Is it the dash brake indicator light, which comes on when the park brake is applied, that is blinking?

RWAL stands for REAR WHEEL ANTILOCK. RWAL was standard equipment starting in 1988 on full size trucks.

The RWAL system can store trouble codes.

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

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.

You can clear the code by removing the fuse for 10 seconds then reinstalling it. The fuse should be labeled STOP/HAZARD or BRAKE. Removing the RWAL fuse will not clear the code.

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

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.

On trucks built after Aug 1994 a scanner is required to retrieve codes 6,9,10

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

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

On this system it is usually best to: Check the code, clear the code, and drive the truck and see if the code returns.

Code 4 = Grounded or closed RWAL valve switch

Do you have a good digital ohm meter for testing?

Do you want test information?
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 the it has been altered from stock let us know about that too.


 
Iceline 
Member
Posts: 65

Loc: Buffalo NY
Reg: 12-17-04
04-01-07 09:40 AM - Post#1133169    
    In response to Chevytech

I am sorry for the lack of info.

I have a 92 3/4, 2 wheel with RWAL. With a 5.7 if that matters.

Yes it is the dash light that is blinking. 3 short and one longer blink. There was a time when the brake light came on and just stayed on. I checked all four wheels and the brakes and surrounding parts looked fine. I cleaned everything, made sure all moving parts were free and used an anti-seize to lube everything. I was told to disconnected the battery for an hour to clear the code and the light stayed off all winter long. Just last week I started the truck and it started to blink.

I am not very familiar with anti-lock. I know how it operates but don't know much about trouble shooting this issue. All information will be a great help I'm sure.

Thank you in advance. I have always found this site very helpful.


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3014

Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
04-01-07 10:35 AM - Post#1133198    
    In response to Iceline

GM RWAL code 4 testing:
The isolation/Dump Valve is out by the master cylinder. It is an aluminum block with two round thinks and has brake lines going to it.

Key OFF, unplug the Isolation/Dump valve, test the resistance between terminal C of the Isolation/Dump valve and the body of the valve. This tests the switch. Also test the resistance between terminal C and terminal D of the Isolation/Dump Valve. Both tests should measure greater then 50,000 ohms. If they measure less than this the Isolation/ Dump valve is bad.

If it tests ok, with the connecter still unplugged, turn the key on, measure the voltage between terminal C and terminal D of the wire harness that connects to the Isolation/Dump valve. It should be 4 volts or more. If it reads 0 volts replace the RWAL ECU (flat black plastic box by the master cylinder). If it tested 4 volts or more, and it sets a code 4 again, after clearing the code, replace the Isolation/Dump valve.

Note: My experience with this system is, if all parts test ok, the module is possibly the problem.

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 the it has been altered from stock let us know about that too.


 
Iceline 
Member
Posts: 65

Loc: Buffalo NY
Reg: 12-17-04
04-01-07 11:48 AM - Post#1133232    
    In response to Chevytech

Chevytech,
Thank you.

Its pouring rain out right now but when I have the results I will post them. Right now I have to go find my ohm meter.

Thanks again!!!!

 
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