SERVICE BRAKE ASSIST / 2020 SIERRA

Denali2020 · April 14, 2020

Hey all! I just got a brand new 2020 Denali off the showroom floor . It has a message in the dash “service brake assist”. It was even on while I took it for a test drive. Long story short Looks like the dealer is replacing the master cylinder. Not sure what the full scope of the techs report is yet, I’ll keep everyone posted. My vin has no recall in the NHTSA, but that can always change..

Edited April 15, 2020 by Denali2020
mis spelled the Sierra

steve841 · April 14, 2020

Amazing they still cant get it right ... the brake system on the 19s was a total foul up of software and master cylinders.

Edited April 14, 2020 by steve841

Denali20 · April 20, 2020

On 4/14/2020 at 3:50 PM, Denali2020 said:

Hey all! I just got a brand new 2020 Denali off the showroom floor . It has a message in the dash “service brake assist”. It was even on while I took it for a test drive. Long story short Looks like the dealer is replacing the master cylinder. Not sure what the full scope of the techs report is yet, I’ll keep everyone posted. My vin has no recall in the NHTSA, but that can always change..

I have the same issue on my 2020, purchased a month ago. Just brought it in with less than 500 miles on it. They “reprogrammed all the modules” and the fault cleared. Two days later, the fault appears again every time I start it. Bringing it in again this week. What led them to replace the master cylinder? Please let us know when you find out.

Denali2020 · April 20, 2020

Hey all! All they told me is that it was a major recall. I think they didn’t want me to be upset, after I only had the truck a week. They replaced brake master cylinder, brake module, and replaced all the brake lines. I’ll say the dealer did a great job, I couldn’t even tell they did all that work, as I also am a former Tech myself. It was Big job especially for a brand new truck with 100 miles on it . I will say the code is gone so far, almost a week now, the code would come back hours later after they cleared it, I’m pretty confident they fixed it. Here is a copy of the report. I would absolutely keep hounding your local dealer to fix the code, it’s in for a reason, and it’s not going to go away!

Denali20 · April 20, 2020

Very helpful, thank you!

Denali2020 · April 20, 2020

My pleasure, I was once in the dark about this. I’m so glad I could help others with this info. Apparently the infamous brake recall they had a couple years ago has lingered into the 2020 models as well. Just be very careful driving it. I did not experience any brake lag or failure, it only had the annoying light on. But I’ve read other posts who had the same light and had brake issues. Aside from that how do you like your truck? I love it, I refuse to let the recall stop me from enjoying it!

newdude · April 20, 2020

41 minutes ago, Denali2020 said:

Hey all! All they told me is that it was a major recall. I think they didn’t want me to be upset, after I only had the truck a week. They replaced brake master cylinder, brake module, and replaced all the brake lines. I’ll say the dealer did a great job, I couldn’t even tell they did all that work, as I also am a former Tech myself. It was Big job especially for a brand new truck with 100 miles on it . I will say the code is gone so far, almost a week now, the code would come back hours later after they cleared it, I’m pretty confident they fixed it. Here is a copy of the report. I would absolutely keep hounding your local dealer to fix the code, it’s in for a reason, and it’s not going to go away!

Not sure as to why they would put lines in? Something must have failed in the brake module to get the module/master assembly though. The recall(s) are nothing more than reprograms to the brake module.

Denali2020 · April 20, 2020

I mis1quoted looks like he reinstalled the lines .. but I was surprised as well as to the amount of work needed from the fix. So something from the previous recalls must have been amended by GM to fix the issue, for all we know this could be a new issue itself..

Denali2020 · April 23, 2020

Just wanted to update everyone. Its been almost two weeks now, and so far the "Service brake assist" Message has not returned.

Andrew -

Denali20 · April 23, 2020

11 hours ago, Denali2020 said:

Just wanted to update everyone. Its been almost two weeks now, and so far the "Service brake assist" Message has not returned.

Andrew -

Thanks for the update. Mine is back at the dealer now for over a day now. I’ll update this thread when I hear what the issue/fix was.

I love it other than this issue that hopefully gets solved soon!

L87Powered · April 24, 2020

I believe this is the Brake System Control Module recall (N202294820).

Should just require a re-flash.

Denali2020 · April 24, 2020

Maybe, but they did way more work than that. I attached the report from the tech in the earlier post of the chain. Keep in mind new recalls and procedures can be issued/changed/modified from the manufacturer at anytime. I believe the original fix was a software update , then that turned out to be disastrous, then there was a replacement fix for that recall...I could be wrong, just thought I read that somewhere. Thanks for the reply!

Andrew -

Denali20 · April 24, 2020

I got mine back from the dealer yesterday. It was generating a new code from when I had it in last week. They replaced the master cylinder, same as the notes posted above. So it appears more than just a re-flash. Hopefully it’s solved now.

Denali2020 · April 24, 2020

Hey!

well I’m glad to hear they took you seriously, and started somewhere to fix it. I’m betting you will be good to go though now! So far I still have no codes after that procedure.

Rixky · May 3, 2020

Brand new Silverado 400 miles. All lights came on. (Trailer brake asst, abs, check engine light) brake pedal was really hard. Truck will not pass 42 mph. Not happy. I used to have a Toyota truck never had a issue in 7 years. I think this truck is a lemon. Going to the dealer on monday.