Clearing Service Brake System message

[Matt06Yukon]

Hey guys, long time no post. I still have my 2006 Yukon, 209,000 miles and its been almost completely trouble free. I did however spring a leak in one of my brake lines. The Service Brake System message came up while driving along with the red Brake light. I fixed the lines, get everything working good again, but the message and brake light hasn't gone away. It chimes at me like 10 times every startup. I tried using my Autotel scanner to clear it but there wasn't an option for that. Also disconnected the battery over night and still no help. Do i need a Scan tool?
Thanks

 

[Scottydoggs]

pretty sure we have a low fluid sensor in the master cylinder, they can get sludged up and just need a wiping off most of the time.

 

[Doubeleive]

if it is a brake warning only and no abs along with it then it is the fluid sensor or the proportioning valve is stuck. the valve is designed to work when a brake line gives out so that could be the case.
2 things you can do.
1. replace the fluid sensor. If the message goes away, great done...
2. if the new sensor does not make the message go away then unplug the fluid sensor, the message should be gone. If so then the prop valve is stuck, you can usually fix it by doing several emergency stops on gravel and/or keep driving it a few days while doing emergency stops intermittently when it is safe to do so.
I have read the correct way to try and get it unstuck is to slowly bleed the rear brakes, some have said it can be done by using a screw drive or whatever to move the valve by hand and others said it couldn't be done that way.
worst case scenario replace the prop valve.

 

[Doubeleive]

in any case no amount of "clearing the code" will work it is a self-checking system just like airbags, it either works or it does not, it's not a code you can clear

 

[Matt06Yukon]

Interesting. I've had this happen before on other vehicles, it seems to happen when the brake pedal goes too far to the floor. Which is exactly why it did it this time, the rear line started leaking and the pedal went down pretty far. I just expected it to reset itself when the pedal pressure was restored. I'll try some emergency stops and see what happens. Thanks.

 

[Doubeleive]

Interesting. I've had this happen before on other vehicles, it seems to happen when the brake pedal goes too far to the floor. Which is exactly why it did it this time, the rear line started leaking and the pedal went down pretty far. I just expected it to reset itself when the pedal pressure was restored. I'll try some emergency stops and see what happens. Thanks.

I had it happen before when I changed the brakes, jumped in and went to drive and didn't realize I hadn't pumped the brakes first and sank the pedal in a oh-sh*t method and jammed the prop valve., driving around and doing a few e-stops here and there on gravel and pavement it corrected it's self in about 3 days.

 

[Matt06Yukon]

I'm going out to the garage now to check the sensor. If thats a no go, I'll try some panic stops. Thanks again.
You did this on a NBS?

 

[Doubeleive]

I'm going out to the garage now to check the sensor. If thats a no go, I'll try some panic stops. Thanks again.
You did this on a NBS?

Yes, but this is the way all 4 wheel brakes are designed, some just do not have fluid level sensor but all have the prop valve as far as i know it's a safety thing so that if a line blows out you can still stop even though the stopping power is reduced, the valve separates the front & rear system, so if you ever want to "get rid" of someone cut a front and a rear line, lol

 

[Matt06Yukon]

Hey, you were spot on. I rolled 50 feet outta my garage, hit the brakes harder than usual and it clicked and reset instantly.
Worked perfect. Thanks again!

 

[flfred]

I had the same Service Brake System message with 2003 Tahoe after a brake line failure. Replaced the lines and bleed. Tried the ABS test on a gravel road. Everything works as it should but the error still was on display. Took it to have it scanned for codes. No codes found. ABS would not talk to the scanner. Mechanic said it looks like a cable or connector problem. He suggested tracing the harnesses from the module to the ECM and look for damage. Pull each connector and clean with electrical contact cleaner. Did all that but found no problem. Removed the plug on the Portioning valve sensor. The error went away. The switch was stuck closed. The switch should be open when the plunger is is not depressed. By removing the switch from the valve you can see into the port. The piston for the portioning valve has a groove in the center. The plunger from the switch drops into it allowing the switch to stay open. I found a Gm Factory replacement switch on Amazon for $17. Problem solved. By the way the description says it is not correct for my vehicle, but it is the exact same part. Link below https://smile.amazon.com/gp/product/B0010GHZIS/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1.