2006 Suburban 4wd Z71 Service stability code C0131

mike6w
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2006 Suburban 4wd Z71 Service stability code C0131

Unread post by mike6w » Sun Nov 01, 2015 8:17 am

I need help figuring out my brake trouble on my suv. My suv has service stability system displayed. Code i am getting is C0131 no other codes. What the suv is doing is when i monitor with a scanner it starts off when cold 100 Kpa on master cylinder switch. As i drive that pressure keeps building and you will eventually only be able to move in low gear and pressure will be as high as 3000 Kpa. The brakes are fully engaged. I have pulled the fuses from ABS and stability system and it still does the same thing. If you let it sit and cool completely down it will start at 100 Kpa again and within a mile or two it will be back to full brake engagement. I also monitored the wheel speed sensors and all are working and reading the same speeds. Any help or suggestions will be greatly appreciated.

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carriedi
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Re: 2006 Suburban 4wd Z71 Service stability code C0131

Unread post by carriedi » Sun Nov 01, 2015 1:33 pm

what does the scanner show when you apply the brakes on and off when you first start up?

without any checking, it sounds like a bad ECMB. You have to do some circuit checking but not a lot of other things can really cause a pressure build up like this. There are things that could be done to look farther into this problem but due to safety and liability reasons I am going to recommend you take it to a shop to look at your vehicle. If you have an accident (or cause one) while checking into this problem, a big lawsuit could be lurking around...

disconnecting things or bypassing things are a diagnostic tool but if something happens while these things are by-passed or disabled, whom ever disabled any part of the brake system will be involved in blame if for any reason an accident happens. Safety first and protect yourself from liability, Have a shop diagnose your vehicle. You can decide to do the repair yourself or not once you find out what they have found out.
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mike6w
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Re: 2006 Suburban 4wd Z71 Service stability code C0131

Unread post by mike6w » Sun Nov 01, 2015 1:46 pm

When you step on the brake pedal pressure goes up and releases when you release the brake. After a few minutes driving pressure keeps rising till you have to keep in low and stomp gas pedal to move.

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carriedi
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Re: 2006 Suburban 4wd Z71 Service stability code C0131

Unread post by carriedi » Sun Nov 01, 2015 2:00 pm

there are not a lot of things that will cause the pressure to go up like that. Pressure on the master from the power booster, seepage out of the port from the abs pump motor...
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mike6w
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Re: 2006 Suburban 4wd Z71 Service stability code C0131

Unread post by mike6w » Sun Nov 01, 2015 2:32 pm

Thanks was just looking for some suggestions or testing so i could isolate without throwing a bunch of parts at it. I have good code readers and was hoping they were capable of pinpointing, i have a snapon reader and the latest autoenginuity on my computer

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carriedi
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Re: 2006 Suburban 4wd Z71 Service stability code C0131

Unread post by carriedi » Sun Nov 01, 2015 6:03 pm

most codes do not give you a definitive fix. they just point you in a direction. Your codes says there is a problem with the pressure reading according to the pressure the computer is looking for. Are there any other codes? If you have other codes you should look at those first. example: codes c0161 or code c0292 should be looked at before you look at c0131.

for code c0131 only, and the increasing pressure you have, I would drive (staying very close to home) and watch the pressure until it acts up as you describe. When you get the high pressure with no brake pedal application (not stepping on the brake pedal) leave the engine running and watch the pressure. Pull the brake pedal up and see what the pressure does. if that doesn't change the pressure, unbolt the master cylinder from the booster and see if the brake pressure drops. If it goes down you may have an improperly adjusted push rod or a bad booster. The brake pressure sensor just reads the pressure. It doesn't make it. So the pressure is going up or the sensor is not doing it's job. Since the vehicle's brakes are being applied I would tend to look at things that apply the brakes. Brake pedal, booster, master...

check the booster first. wh
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mike6w
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Re: 2006 Suburban 4wd Z71 Service stability code C0131

Unread post by mike6w » Mon Nov 02, 2015 9:43 am

thank you very much i'll check that out and let you know what and if anything i find

mike6w
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Re: 2006 Suburban 4wd Z71 Service stability code C0131

Unread post by mike6w » Mon Nov 02, 2015 11:54 am

ok I recreated the trouble and did what you suggested. I loosened the master cylinder at the power booster and the pressure goes away and suv drives fine. Now trying to figure out if that means the power booster or master cylinder are bad or if that means I just need to adjust the rod on the master cylinder?

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carriedi
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Re: 2006 Suburban 4wd Z71 Service stability code C0131

Unread post by carriedi » Tue Nov 03, 2015 11:43 am

Now that you know where the pressure is coming from you have to decide if you need to adjust the booster pushrod to the master, the master is leaking and there is brake fluid in the booster or the booster is bad and the control valve is leaking. So, a bad booster, a bad master or an adjustment. Some boosters are not adjustable. In that case I would try replacing the booster. If there is no brake fluid in the booster I would try to shorten the booster pushrod very slightly. If there is brake fluid in the booster I would replace the master and clean out the fluid from the booster. If the booster is dry inside I would try to adjust it slightly. Very slightly. You are dealing with your brakes and safety should always be your first concern. If the booster is dry and the pushrod is not adjustable I would replace the booster.
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