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Old 08-12-2008, 10:07 AM   #1
fris_94
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brake warning light

My brake warning light came on about 2 days ago and stayed on. I don't have any visible leaks and theres enough brake fluid in her that it shouldn't trigger the light. Now last night when I was coming back from work the light started to flash. It will flash for about 10 quick flashes then 1 longer flash. Anyone have this happen or know whats happening.
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Old 08-12-2008, 10:51 AM   #2
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Re: brake warning light

If the instrument panel brake indicator light is blinking check the RWAL system for trouble codes.

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.


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.

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.

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

If you have a code 10 that would be a brake switch circuit code.

A code 11 has to do with the speed sensor circuit – does the speedo work correctly?

What year is your truck?
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Old 08-12-2008, 09:32 PM   #3
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Re: brake warning light

Chevy Tech,
Not to rob the post, but this one caught my attention. On my 91 model, I have a similar problem with the brake warning light staying on continuously. Brakes work great, plenty of fluid etc., any ideas as to what might cause that problem and how do you troubleshoot it? Thanks.
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Old 08-12-2008, 09:38 PM   #4
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Re: brake warning light

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Originally Posted by 6772fan View Post
Chevy Tech,
Not to rob the post, but this one caught my attention. On my 91 model, I have a similar problem with the brake warning light staying on continuously. Brakes work great, plenty of fluid etc., any ideas as to what might cause that problem and how do you troubleshoot it? Thanks.
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?

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.

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

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

If it has no code stored let me know and I can give you more tests.
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Old 08-13-2008, 09:39 PM   #5
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Re: brake warning light

Great information, Chevy Tech. I'll troubleshoot it this weekend. Thanks so much.
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Old 08-15-2008, 11:33 AM   #6
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Re: brake warning light

GREAT info ! I printed it out for future use. Thanks
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Old 08-15-2008, 04:12 PM   #7
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Re: brake warning light

I unplugged the wire harness from the porportional valve and the light went out. Put the harness back in and the light hasn't come on since. Im thinking that something must have happened, like a hard brake, to offset the valve. i haven't had a problem since. I'll update if this changes lol.
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Old 08-15-2008, 10:22 PM   #8
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Exclamation Re: brake warning light

upon smogging this truck, will this cause to fail visual test and not get smog certificate? I have an 89 with the brake light flashing and I need to transfer to my name.
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Old 08-16-2008, 10:15 AM   #9
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Re: brake warning light

Quote:
It will flash for about 10 quick flashes then 1 longer flash. Anyone have this happen or know whats happening.
Quote:
I unplugged the wire harness from the porportional valve and the light went out. Put the harness back in and the light hasn't come on since. Im thinking that something must have happened, like a hard brake, to offset the valve. i haven't had a problem since.
If it was a code 11, the problem is most likely a speed sensor or “DRAC” issue.

If you unplugged the RWAL module when you were unplugging the combination valve you cleared the memory. Note unplugging the RWAL module is not the recommended method for clearing the memory.

Last edited by ChevyTech; 08-16-2008 at 10:16 AM.
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Old 08-16-2008, 10:18 AM   #10
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Re: brake warning light

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Originally Posted by mexgrhd68 View Post
upon smogging this truck, will this cause to fail visual test and not get smog certificate? I have an 89 with the brake light flashing and I need to transfer to my name.
The brake system really is not part of the pollution equipment so my guess is it would not be a problem, but I don’t know this is only my best guess.
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Old 08-16-2008, 10:25 AM   #11
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Re: brake warning light

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Originally Posted by jgrh64 View Post
GREAT info ! I printed it out for future use. Thanks
Thanks

I have other links to RWAL information.

I also have many pages or RWAL information I have saved from replying to RWAL posts on various boards.

If you have RWAL questions post them, and I will reply with what is pertinent, but I have so much that it is to much for posting it all at once.

Last edited by ChevyTech; 08-16-2008 at 10:27 AM.
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Old 08-18-2008, 01:43 PM   #12
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Re: brake warning light

mine flashes 7 at me. it was on all the time till about a week ago then started flashing 7. it was flashing when i bought the truck and i just bought a scanner and cleared the codes. then the light just stayed on. now its flashing again. i did some reading and checked rear brakes, they where a bit on the loose side , tightened them up and that helped with the soft pedal but the light is still on and flashing now.
any ideas ?
thanks
lance

Last edited by QKENUF4U; 08-18-2008 at 01:44 PM.
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Old 08-18-2008, 02:24 PM   #13
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Exclamation Re: brake warning light

Quote:
Originally Posted by ChevyTech View Post
The brake system really is not part of the pollution equipment so my guess is it would not be a problem, but I don’t know this is only my best guess.
I disconnected battery for 5 seconds, reconnected, light issue is gone. No more flashing since!!
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Old 08-18-2008, 04:14 PM   #14
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Re: brake warning light

Quote:
Originally Posted by QKENUF4U View Post
mine flashes 7 at me. it was on all the time till about a week ago then started flashing 7. it was flashing when i bought the truck and i just bought a scanner and cleared the codes. then the light just stayed on. now its flashing again. i did some reading and checked rear brakes, they where a bit on the loose side , tightened them up and that helped with the soft pedal but the light is still on and flashing now.
any ideas ?
thanks
lance
Hi Lance

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.

For me I have always found the same code.

If it has one long flash and six short flashes this would be a code 7.
Code 7 = Shorted isolation valve or defective ABS module.

The isolation and dump valve are in the same part. It’s located out by the master cylinder.

The isolation/dump has 4 wires going to it and has two solenoids on it

If you have a good digital volt ohm meter here are some tests you can do.

Key off, isolation dump valve unplugged, probing the wire connector that is on the Isolation dump valve.
Terminal A to terminal D - should be 3 to 6 ohms.
Terminal A to the valve housing – should be greater than 50,000 ohms.
If the resistance is to low on either of these tests, the valve is shorted. – replace it.

Isolation dump valve disconnected, Key on, ALDL Terminal H connected to terminal A – test voltage between terminal A and D of the harness that goes to the isolation dump valve. You should have one volt or more. If it fails this test it points to the RWAL module.

If it passes all tests, clear the code and see if the same code comes back.
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Old 08-18-2008, 04:19 PM   #15
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Re: brake warning light

Quote:
Originally Posted by mexgrhd68 View Post
I disconnected battery for 5 seconds, reconnected, light issue is gone. No more flashing since!!
The early RWAL systems set more false codes then later RWAL trucks.

On these trucks it is always a good idea to see if it will reset the code before you buy ANY parts for repairing a RWAL problem.
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Old 09-04-2008, 12:42 AM   #16
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Re: brake warning light

my dads brake lights in his 91 has been on since 97, thought the light would of burned out years ago
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Old 10-13-2009, 03:23 PM   #17
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Re: brake warning light

hey guys, i know its a super old thread, but chevy tech seems to have alot of information on these trucks and I'm hoping he will chime in..

My truck is a 98 GMC 4x4 1500 equiped with ABS brakes.

the ABS light is not on.. but when i stop every once in a while the abs will come on and limit braking even though the wheels are not skidding or locked up. I mean literally under a normal stop at a stop light the abs will just randomly start making noise and feel in the pedal, and the truck will all but stop braking completly. really scary.

I have simply pulled the fuse out for the ABS in the fuse panel and now the light has come on..

what could be causing this problem?
why would there be no lights on at all and the abs be coming active on dry pavement?

any help or tips would be appreciated.
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Old 10-13-2009, 05:57 PM   #18
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Re: brake warning light

Hi 69halfton

It sure sounds like your 1998 has a front wheel speed sensor problem.

Rust is a common problem causing this type of complaint.

Check to see if any trouble codes have been stored, even if the ABS light is not on now.

See the information in the links below.

Here is a link to the recall about ABS activating to easily that covers trucks starting with the 1999 model year.
http://www-odi.nhtsa.dot.gov/cars/pr...0&summary=true

This link shows the problem covering older models back to 1995.
http://www.justanswer.com/questions/...-z71-silverado
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Old 10-13-2009, 07:19 PM   #19
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Re: brake warning light

thanks chevytech, that is exactly the information i was looking for. I'll do some work on the truck this weekend and see what I come up with, i might have more questions...but I'll let you know.
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Old 10-17-2009, 12:17 PM   #20
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Re: brake warning light

ok, someone please help with this....94 chevy k1500, 305 auto and rwal brakes. we can only get 1/4 to 1/3 pedel brakes at best. abs light is not on and never has been. constantly seem to be bleeding the brakes, more routene than oil changes. is this normal with rwal brakes or is it a problem. the master cyl has been replaced as well as the abs valve and all the brake lines. help.... i am hating this abs system more than anything esle i've ever worked on. it's my sons truck and its driving me crazy.
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Old 10-17-2009, 07:01 PM   #21
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Re: brake warning light

Quote:
constantly seem to be bleeding the brakes, more routene than oil changes. is this normal with rwal brakes or is it a problem.
No, that is not normal.

Quote:
the master cyl has been replaced
There have been many bad rebuilt master cylinders lately. My guess is that the replacement master cylinder is not good if it keeps getting air in the system.

Note: It is very important that the rear brake shoes are properly adjusted on these trucks.
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Old 10-18-2009, 10:52 PM   #22
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Re: brake warning light

hey chev...
just me lance again...lol ... brake light was solid till i cleaned/adjusted my rears tonight . now its flashing 13... what ya got for me on that one ???? thanks man....
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Old 10-20-2009, 10:02 AM   #23
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Re: brake warning light

Hi Lance

If it is a RWAL system:
13 = ABS module speed processor (Dodge & Ford only)


If it has 4 wheel antilock brakes then 4WAL code information must be used. Be careful that you use the correct model year information.
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Old 07-05-2012, 01:50 AM   #24
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Re: brake warning light

Hello CT, I have a 1991 Chevy S-10, 2.8L, 2 wheel drive, 5 speed standard trans with gas carb. I am also having problems with my brake light staying on, I can step on the e brake and the light stays on the same brightness. I've check the code on the ecm and it comes up with code 7. I reviewed the posting that was sent at the beginning by QKENUF4U of this section and some of this I might be able to use but my isolation/dump valve is not the same as the one that is mention on the earlier posting. I don't know which way to go as far as replacing these parts or which should be replaced. I know where to buy a ecm unit but the isolation/dump valve is not so easy to find or I'm not looking in the correct place. What advice do you have on this situation.

Thanks
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Old 07-05-2012, 10:21 AM   #25
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Re: brake warning light

Quote:
Hello CT, I have a 1991 Chevy S-10, 2.8L, 2 wheel drive, 5 speed standard trans with gas carb. I am also having problems with my brake light staying on, I can step on the e brake and the light stays on the same brightness.
Hi & welcome to the board.
If this is true then there is also a problem with the park park or park brake switch.

Quote:
...my isolation/dump valve is not the same as the one that is mention on the earlier posting...
On early S/T trucks it is mounted sideways under the metering & proportioning valve (combination valve) . An S /T truck my look different then a full size and different models years also may be different.
Quote:
I don't know which way to go as far as replacing these parts or which should be replaced. I know where to buy a ecm unit but the isolation/dump valve is not so easy to find or I'm not looking in the correct place. What advice do you have on this situation.
These parts are getting harder to find. I like grabbing extra parts at the local U-Pull-It but I have never come across a Isolation dump valve that was not rusty or corroded.

Here is code 7 testing information:
Code 7

The isolation and dump valve are in the same part. It’s located out by the master cylinder. The isolation/dump has 4 wires going to it and has two solenoids on it. The combination valve has one wire going to it and is more long and skinny.


If you have a good digital volt ohm meter here are some tests you can do.

Key off, isolation dump valve unplugged, probing the wire connector that is on the Isolation dump valve.
Terminal A to terminal D - should be 3 to 6 ohms.
Terminal A to the valve housing – should be greater than 50,000 ohms.
If the resistance is to low on either of these tests, the valve is shorted. – replace it.

A = Green wire
B = White wire
C = Blue wire
D = Black wire

Here is the way the wires are positioned on the RWAL module:
D = Black wire
C = Blue wire
B = White wire
A = Green wire

Isolation dump valve disconnected, Key on, ALDL Terminal H connected to terminal A – test voltage between terminal A and D of the module where the harness that goes to the isolation dump valve plugs in. You should have one volt or more. If it fails this test it points to the RWAL module.
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