At a loss service brake system

[swathdiver]

So the sensor is bad then? I'm a little slow to understand, sorry.

 

[fire730]

I would go find a gravel / wet road in a safe area and jam the brakes a few times to cycle the system. Make the abs system work. I would do that before I started throwing parts at the truck.

 

[Doubeleive]

So the sensor is bad then? I'm a little slow to understand, sorry.

the valve is jammed, the sensor is working.
the valve distributes the brake pressure to all 4 calipers (basically front or rear), it is a safety valve that is designed to prevent brake failure, so lets say I blew the left front brake line, the valve would move and direct brake pressure more to the back brakes so I could still stop safely. when it moves it then touches the sensor and sets a error.

 

[Doubeleive]

I would go find a gravel / wet road in a safe area and jam the brakes a few times to cycle the system. Make the abs system work. I would do that before I started throwing parts at the truck.

ya I gave it a few slams and bangs it's stuck, it needs the whole system cleaned out anyway so going to see about it tomorrow I don't have any helper (other than a 6yr old) or a bleeder setup

 

[Rocket Man]

Betcha about crapped your pants when the pedal went to the floor as you were headed toward the Denali!

 

[Doubeleive]

Betcha about crapped your pants when the pedal went to the floor as you were headed toward the Denali!

yessir! sudden realization I ****** up, lol I am pretty sure that's when the valve stuck (panic pedal)

 

[Doubeleive]

Is there a way to test the valve in one of the other menus in the Tech2?

I doubt it since it is a mechanical valve, I could unscrew the sensor but not sure if that would introduce air into the system or not

 

[swathdiver]

the valve is jammed, the sensor is working.
the valve distributes the brake pressure to all 4 calipers (basically front or rear), it is a safety valve that is designed to prevent brake failure, so lets say I blew the left front brake line, the valve would move and direct brake pressure more to the back brakes so I could still stop safely. when it moves it then touches the sensor and sets a error.

Oh OK, when I was a kid that part was called the proportioning valve and it was mounted on the frame under the driver on my old Buick. I had to replace the one in my '79 once.

 

[Doubeleive]

Oh OK, when I was a kid that part was called the proportioning valve and it was mounted on the frame under the driver on my old Buick. I had to replace the one in my '79 once.

the test from what I gathered is to just unplug it, you can test it with a lighted probe to see if moves back to the correct position when bleeding the lines or it may make a pop sound when going back into the correct position from what I was reading. another thing that makes me pretty sure that it's stuck is the sensor is basically saying "low pressure" with just the key on, if it was the master cylinder or something else I would think it would only say low pressure if the engine was running and vacuum was present.

 

[02Lightning]

I’ll bet you can force that valve the other direction, by opening the opposite side of the system and pushing the brakes to the floor with a rear bleeder open. Closing it of course before letting the pedal up.