2020 GMC Terrain Brakes Problems

While driving I received a "service brake assist system" alert and a check engine light. After this happened the brakes were extremely hard to press. I had to put my entire weight on the breaks to stop the car. The brake "assist" feature really is making the brakes functional. We were able to safely get to the side of the road. We found a vacuum pump failed and needed to be replaced. There was no sign that this was failing; it worked, then it didn't.

The contact owns a 2020 GMC Terrain. While the contact’s wife was driving approximately 40 MPH and attempting to depress the brake pedal to pull into the parking lot of Walmart, the braking distance was extended while bringing the vehicle to a complete stop. The driver used excessive force on the brake pedal using both feet. The vehicle was towed to a certified mechanic, who diagnosed the vehicle and determined that the brake vacuum pump had failed. The vacuum pump had fractured where it was connected to the camshaft, causing pieces to enter the engine. The brake vacuum pump and the connector were replaced. The manufacturer was made aware of the failure. The failure mileage was approximately 156,000.

While driving down the interstate a notice popped up on my dash about the brake assist. When I attempted to slow down the vehicle to safely pull over the brake pedal was very hard to push. I was able to slow the vehicle to a complete stop but needing to use both feed and press hard with all my weight. Once the vehicle was parked and shut off I turned it back on to have the check engine light pop up on the dash. I contacted Onstar and was towed to a dealership. The brake vacuum pump had broken off at the cam shaft and required extensive repairs. It is my understanding that this is a common occurance and there were previous recalls on the other style Terrains due to the same issue. yet they used the same part on the newer body style being fully aware of the design flaw.

Since August 2024, my brake booster has gone a total of five times each time with the notification on the dash service brake assist. And it just went again as of two days ago. I’ve brought it to Firestone where they have replaced it each time with a warranty on the part. I called them yesterday to tell them that it went again and they refused to fix it telling me that they got the part from the dealership and that I would have to take it there so the dealership would have to figure out what’s wrong with it as to why the car is “chewing up” the part. I have young kids and this part has gone five times.

While driving my brakes failed. I was unable to stop my car, my brake pedal became very stiff and I could not stop my car. There were no warning signs or lights on indicating there were any issues with my car prior to this happening. I had to have my car towed to the dealer. The current estimate is for a vacuum pump failure resulting in camshaft damage. Both need to be replaced. I see other GMC cars were recalled for what appears to be a similar issue. I am lucky no one was injured as this could have very easily resulted in a fatal event. I have never heard of such a thing happening before and am beyond belief that this has occurred. This is the third repair I've had done this year. I have also replaced a booter pipe and valve gasket due to leaking oil. The amount of repairs required in such a short a time seems excessive.

While driving on a main road at around 45mph the vacuum pump that supplies brake fluid to the brakes failed. The car was unable to be stopped and had it not been late in the night I could have crashed into other vehicles on the road or hit someone walking. There was not indication prior to the malfunction and was very sudden. This issue has been observed by the dealer as well as multiple other individuals with the same problem for this make and model of car as well as others by the same manufacturer for similar years of manufacturing. This part has also been shown to break into the engine causing complete engine failure due to lack of a shear pin on the vacuum pump.

The contact owns a 2020 GMC Terrain. The contact stated that while driving up the driveway at approximately 10 MPH, the brake pedal was depressed but failed to function as intended. The contact used force to depress the brake pedal. When the vehicle came to a stop, there was an abnormal grinding sound coming from the front brakes. The contact stated that the message "Power Assist Brakes" was displayed on the instrument panel. The vehicle was not taken to the dealer or an independent mechanic. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 198,000.

Vacuum pump went out. It was a recall, previously on older models, but this model needs to

I filed a complaint with NHTSA on November 3, 2025, about my brake system. Here is another one adding more information. I had to have another brake system part replaced. This time it was the brake booster. Cost $1441.63 (covered by extended warranty actual cost to me $100.00.) So far, I have had the booster sensor replaced twice, the vacuum pump and now the brake booster. I asked the mechanic how many parts related to this system were left to replace? This vehicle has 66,000 miles on parts for the braking system started needed to be replaced at 37,000 miles. The total cost for parts, labor is about $500. That does not include the loss of use for this vehicle which is about 15 days. Taking days off of work about 6 days. This has been a problem for GMC Terrains since 2015; there is still a problem with 2020 model year. Please do something before there is a loss of life due to brake failure.

Check engine light is on took vehicle to dealership 10/13/2023 vacuum booster sensor replaced (37,435 miles) $0 GM Covered cost 12/9/2024 brake vacuum pump replaced (56,456 miles) $0 extended warranty 1/8/2025 vacuum booster sensor replaced (57,087 miles) $252.48 not covered by warranty Check engine light is on 10/11/2025 took to dealership. They were unable to find issue light was off, was told that GM had recommended several things that could be the cause of light coming on still could not find issue. Last thing GM and dealership recommended was to replace the battery. Cost $104.00 Check engine light came on 10/25/2025 while returning home from Tennessee to Michigan, light came on in Louisville, KY. Had it scanned, booster sensor was the cause. Called AAA had them replace battery light went off. (as you know that if you do that it reset the computer not surprised light went off drove rest of the way home to Michigan) Cost of replacement battery $295.00 Check engine light came on again 11/2/2025 my best bet is that it is booster sensor again. NHTSA and GM need to fix this issue. I have not lost breaking ability yet but the horror story that I've read on this site scars me. WHAT ARE IS NHTSA AND GM GOING TO DO WAIT UNTIL SOMEONE IS KILLED BECAUSE OF THIS ISSUE !!!!!!!!

On my 2020 GMC terrain the vacuum pump failed and caused my braking system to go out completely. I had to almost stand up on the brakes to get the car to stop and thankfully I got it come to a stop before smashing into another car. I contacted gmc and while they know this is a ongoing problem and there is a warranty out for this particular problem (150,000 miles or 10 year warranty) I was told it is part/ factory specific and that if it was manufactured in certain facilities or had certain parts that they would cover the cost to fix it but however my vehicle was not covered. This poses a dangerous problem for GMC owners. As soon as the check engine light came on I had absolutely no control over the brakes and it was a miracle it stopped. There was no warning prior to this incident and upon looking up information this seems to be a recurrent problem that GMC needs to address seeing as they say they value their customers.

My 2020 GMC Terrain brakes pump failed causing me to hit the median wall on the highway.

While driving my 2020 GMC Terrain (VIN: [XXX] ) with approximately 110,501 miles, I experienced a sudden and complete loss of brake assist. After about 2 hours of highway driving, I exited and the brake pedal became extremely hard to press, making it very difficult to stop. No warning lights or messages appeared before the failure. The dealer diagnosed the cause as the brake booster vacuum pipe exploding internally, which immediately eliminated vacuum to the booster. This created a serious safety hazard and nearly caused a crash. I have since had the part replaced, but the fact that this component can fail without warning at highway speed is alarming. GM has issued TSB 21-NA-107 describing this exact failure mode, which indicates it is a known issue. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Driving down the road and an engine power reduced light came on and then the driver was not able to apply the breaks to stop the car. Almost ran into a car at a 4 way stop before getting the car to stop.

Driving down busy highway and suddenly had no brakes!!! No lights came on dashboard as a warning. Found out it was a braking pump that broke and shot metal pieces into the engine. Now im facing a new engine for a 2020 terrain!!

I was driving on the expressway, attempted to brake and the brakes were stiff and would not go down to stop the vehicle. . Thankfully, I was able to glide over three lanes of traffic and exit the expressway and glide into a parking lot and drove around until the car came to a stop. No lights. No warning. The car had to be towed to my mechanic. This could have been catastrophic. I could have killed someone else or myself. This is the second time that this has happened with this vehicle!!! By the grace of God I am still here writing this complaint. I am traumatized and do not feel safe driving this car. They MUST RECALL this vehicle before somebody gets killed. The issue is with the vacuum pump and I have seen other complaints about the same issue.

As I was driving down the Ohio Turnpike on my way to work on Tuesday, August 5, 2025, my check engine light came on. Almost immediately I got a notification that the car was operating at reduced power. I had no previous issues with the vehicle. As I got off the turnpike my braking system failed. I was able to come to a stop partially in the grass before entering into oncoming traffic. The entire car shut down. I was unable to restart the car. We were also unable to put the car into neutral to push it off of the road the remainder of the way because the wheels were completely locked up at this point. The parking brake was engaged on its own. We also could not get the car into neutral. I had the car towed to a local repair shop, not knowing at all what the issue was. The vacuum pump had failed and broke apart in the engine. This caused my braking system to fail completely also. The vacuum pump on my 2020 GMC terrain has been noted as faulty or defective. However, an official recall has not been issued for my vehicle. Had the pump failed a moment sooner I could have been in a crash trying to exit the turnpike. I took my vehicle to a repair shop and spent $1400 out-of-pocket. The car still does not run correctly now as there are pieces in the engine of my vehicle that were unable to be retrieved.

I was driving on the highway & my brakes failed. My brake pedal was completely hard & could not be used. i had to steer onto an exit ramp & be towed to the dealership. There was absolutely no warning of this happening. Once at the dealership, they confirmed it was my vacuum pump that blew up, which damaged the camshaft & caused pieces of metal to be floating around in my engine. The greater portion of the repair was covered under warranty, however, I had to pay $350 out of pocket. This could have been catastrophic. I or others on the road could have been injure for worse. This system failure should be fixed immediately and owners be compensated. I do not feel safe driving myself or my family in this vehicle after experiencing this occurrence.

I got off a highway exit ramp and with no warning my brakes were hard to press. There was no warning lights on my dash. The brakes take a lot of force to push for a stop. The warning light finally came on a day later with codes p0556 and u040171.

On Monday 5/26/2025 I was on the way home from work, coming down my street to turn in my drive (at approximately 2130) I pushed on the brake getting ready to make my turn, my car would not stop. It traveled maybe 100 -200 feet before coming to a stop. The brake pedal would not push in. (As I live on a cul-de-sac, if this happened during the daylight, there would have been children playing in the street and I could have killed someone's child). I managed very slowly to reverse the car and finally get it in the driveway. I thought it was going to hit my house!! Upon reading a lot of issues and complaints on my vehicle make/model I pretty much figured it was the brake vacuum pump. I called GM, however my car has 74,000 miles, is out of warranty and no recalls for my VIN so I'm told I have to have it fixed. My neighbor is a certified mechanic and has a shop. He looked at it and confirmed it is the vac pump. Not only that but the end that goes into the motor has sheared off and not there is metal pieces and fragments in my motor. I had to have it towed to his shop. (this morning) As of right now I am waiting to see if the motor can be flushed or if I am going to end up having to replace motor. I have missed several days of work due to transportation and now have to rent a car, and pay who knows how much for repairs which could easily cost thousands. I live week to week and still make payments on this car!! This is a faulty part and should have been a recall as I have read on many many complaints of bad brake vacuum pump on the GMC Terrains even the 2020 models and up. Some of the others are already recalled but not mine. In the photos, on one you can see the big chunk of metal. On another where the piece came of of motor you can see where metal was scraping the camshaft in the motor and very small metal fragments around the opening