2015 Sierra Hard Brake Pedal???

amg1107 · November 5, 2018

Just had this happen. Going under 15mph, applying the brake causes the pedal to become stiff and lock up and not work. This has caused me to almost hit someone twice. Sounds to me like brake booster. Anyone else having/had this problem???

ShubiSnax · November 5, 2018

With your truck turned off, pump your brake pedal until it's firm and hold it there. Start your truck while still holding the pedal down and if the pedal doesn't move forward or get softer once the truck is started, then you have bad brake booster.

It could also be your ABS kicking in at lower speeds. This is usually caused by rust buildup around the wheel speed sensor causing it to move, giving a false signal to engage ABS.

amg1107 · November 5, 2018

Its the brake booster then! When I googled it, seems like a lot of people are having the issue, someone even has a lawsuit against GM over this.

I called GM and they ofcourse gave me the run around. Its a shame you spend 50K on a vehicle and you have to put more money in it constantly to replace their cheap parts.

Sierra Dan · November 5, 2018

+2 on the Booster Vacuum Pump.

When they go out, sometimes metal shavings can enter the engine causing harm.

The booster is lubricated with engine oil.

See below:

GMCustomerService · November 6, 2018

20 hours ago, amg1107 said:

Its the brake booster then! When I googled it, seems like a lot of people are having the issue, someone even has a lawsuit against GM over this.

I called GM and they ofcourse gave me the run around. Its a shame you spend 50K on a vehicle and you have to put more money in it constantly to replace their cheap parts.

Hi, amg1107. As a valued customer, we would be more than happy to further investigate your brake pedal concerns. If interested, feel free to send us a private message. Thanks.

Anthony J.

dbrobins27 · November 7, 2018

I had the same thing happen over the weekend. While sitting in stop and go traffic and easing forward the pedal became hard to push and there was little power assist. Once I got moving it didnt return until I was pulling into a parking space later and the same thing happened so I have narrowed it down to low speeds and it does it more frequently in reverse. I suspect it to be the vacuum pump as others have mentioned here but i will find out as its at the dealer for service tomorrow. For what its worth mine is a 2014 CCSB 5.3 4x4 with 80k.

amg1107 · November 7, 2018

42 minutes ago, dbrobins27 said:

I had the same thing happen over the weekend. While sitting in stop and go traffic and easing forward the pedal became hard to push and there was little power assist. Once I got moving it didnt return until I was pulling into a parking space later and the same thing happened so I have narrowed it down to low speeds and it does it more frequently in reverse. I suspect it to be the vacuum pump as others have mentioned here but i will find out as its at the dealer for service tomorrow. For what its worth mine is a 2014 CCSB 5.3 4x4 with 80k.

Please let me know. Interesting to find what fixes it. So far I have had the booster replaced, and it has so far fixed it.

2017Darkness · November 7, 2018

It's the vacuum pump...I write service for a Chevy dealer.

sk · November 7, 2018

1 hour ago, 2017Darkness said:

It's the vacuum pump...I write service for a Chevy dealer.

This. Have your dealer look up PIT5361 (I attached Revision B but there may be a newer version). It tells the Techs to look for oil in the booster line. If they find it they need to replace 5 or 6 parts. It is not a cheap or quick fix but it should be covered if you are still under warranty. I had mine done last year and it FINALLY fixed the problem. My brakes have been fine ever since. As a side note it also eliminated an annoying ticking sound that the dealer kept telling me was from the DI engine but according to this PIT must have been the booster pump.

PIT5361B Brakes.pdf

Edited November 7, 2018 by sk

2017Darkness · November 7, 2018

22 minutes ago, sk said:

This. Have your dealer look up PIT5361 (I attached Revision B but there may be a newer version). It tells the Techs to look for oil in the booster line. If they find it they need to replace 5 or 6 parts. It is not a cheap or quick fix but it should be covered if you are still under warranty. I had mine done last year and it FINALLY fixed the problem. My brakes have been fine ever since. As a side note it also eliminated an annoying ticking sound that the dealer kept telling me was from the DI engine but according to this PIT must have been the booster pump.

PIT5361B Brakes.pdf

Yeah, we check the line for oil and replace it. They don't always push oil all the way into the booster...depends on how long the issue has been going on. Glad you got your issue handled.

dbrobins27 · November 9, 2018

On 11/7/2018 at 1:16 PM, amg1107 said:

Please let me know. Interesting to find what fixes it. So far I have had the booster replaced, and it has so far fixed it.

The truck was repaired today, vacuum pump booster and the belt were replaced.

carnau · March 9, 2019

On 11/5/2018 at 3:01 PM, amg1107 said:

Just had this happen. Going under 15mph, applying the brake causes the pedal to become stiff and lock up and not work. This has caused me to almost hit someone twice. Sounds to me like brake booster. Anyone else having/had this problem???

Hey, Just created a video for this repair. Hope this helps you.