The brake vacuum pump had a catastrophic failure which resulted in the immediate loss of all brakes in the vehicle. I had the vehicle repaired only to find that GM has issued numerous repair bulletins to dealers and mechanics. This appears to be an issue known to them. As the vehicle was repaired, the parts are no longer available for inspection. This was a danger to me and others around me because I was traveling 60mph down hill with no means to slow or stop. I narrowly avoided an accident. There were no warning lamps before the incident. A warning lamp did come on after the loss of brakes but only after I attempted to brake.
2020 GMC Terrain brakes complaints
Page 2 of 4: complaints 11 to 40 of 73, newest first, as owners wrote them.
On June 7, 2026, I was driving my 2020 GMC Terrain. I was going at about 40MPH along a very busy main road. While slowing for a red light the Check Engine Light turned on and the car displayed a notice about reduced engine power. Seconds later, the brake pedal became stuck and would not press down all the way and I lost braking ability. The car rattled/shook violently, made a grinding noise, and then the engine shut off and the car stopped abruptly, narrowly avoiding hitting the car in front of us. I turned on the hazard lights. I was not able to get the car to start again, nor was I able to get the car to shift into any other gear including neutral. We were nearly hit by other vehicles multiple times while attempting to get the car to move again, and to get myself and my child safely out of the road. Myself and multiple bystanders attempted to engage the transmission interlock override multiple time. We were eventually able to engage it and push the car to the side of the road. This failure created an extremely unsafe situation for all involved as this road is very busy and there were numerous near-collisions both with my disabled vehicle, and with other drivers serving out of the way and into other lanes at the last second. As time went on and the battery drained, most of the car's exterior lights turned off and other drivers had a hard time seeing my car. I used a strobe flashlight to alert other drivers but this required that I had to stand in the road near the vehicle. Police were called immediately when I found that we could not move the car out of the road, but they did not arrive. Ultimately the vehicle was stuck and inoperable in a travel lane for over two hours. The car was then towed to a nearby repair shop. The mechanic evaluation stated that the brake vacuum pump had failed resulting in loss of braking ability and expensive damage to the engine and other components. The manufacturer is aware of this issue. See: Thieme, et al. v. General Motors LLC.
I am a [XXX] resident. While commuting to work in [XXX], my GMC Terrain experienced a sudden, catastrophic failure of the brake vacuum pump while traveling at highway speeds. When I attempted to slow down for the exit, the brake pedal instantly became extremely stiff and nearly impossible to depress. I realized I had suffered an absolute loss of power braking assist. To avoid a high-speed collision with heavy highway traffic, I was forced to deliberately steer onto the roadside rumble strips, relying on tire friction to slow the vehicle down. This severe near-miss left me terrified and distraught. Because the shoulder was narrow, my disabled vehicle was left partially protruding into the active roadway. Passing cars sped by so close that my vehicle was violently rocking, creating an incredibly unsafe situation. I was forced to call the State Police for emergency assistance. They dispatched a trooper and a tow truck to remove me and the vehicle safely from the highway. The vehicle was towed to a mechanic in Massachusetts. The mechanic discovered that the vacuum pump had internally exploded. This explosion sent catastrophic metal shards and debris directly into the engines oil galleys and oiling system. While the vehicle has 121,776 miles, this is not a normal wear-and-tear component failure. The brake vacuum pump suffered a catastrophic internal mechanical explosion at highway speeds, completely eliminating my ability to stop the vehicle. A mechanical component failure should never cause an immediate, life-threatening loss of brake control, regardless of mileage. This is a known, systemic engineering defect that is currently the subject of active federal class-action litigation (XXX v. General Motors LLC). This defect did not just cause an immediate life-threatening braking failure, it completely contaminated the oiling system, destroyed the entire engine, and rendered the vehicle a total loss requiring a full engine replacement. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552
I am submitting this complaint regarding a serious and dangerous brake failure involving my 2020 GMC Terrain SLT with approximately 150,000 miles. While driving, the vehicle suddenly experienced a vacuum pump failure that caused a severe loss of braking ability with no warning beforehand. The brake pedal became extremely hard, and the vehicle would barely stop. This created a very dangerous situation and could have easily resulted in a serious accident. Thankfully, I was not driving at a high speed when the failure occurred, and there were no vehicles directly in front of me at the time. However, only minutes earlier I had been traveling approximately 65–70 mph on the highway. If this brake failure had occurred while driving at highway speeds or in heavy traffic, I truly believe it could have caused a major crash resulting in serious injury or death. What concerns me most is that there was no warning before the brakes failed. No warning lights and no issues with my brakes. The sudden loss of braking power was extremely frightening and created an immediate safety hazard. After researching this issue, I discovered that other GMC and GM vehicle owners have reported similar vacuum pump failures and brake assist problems. I believe this is a significant safety issue that should be investigated further. Drivers should not experience sudden brake failure without warning, especially on a vehicle that otherwise appeared to be operating normally beforehand. I am very thankful no one was injured in my situation, but I am concerned that another driver may not be as fortunate. My vehicle had to be towed to a nearby shop and they suspected it was the vacuum pump failure and the car started smoking badly. so I had it towed to the GMC dealership and they called me today to confirm that was the problem and it also caused damage to the camshaft. This is a known issue with the terrain and there is currently a class action lawsuit.
The vacuum pump for the brake system failed catastrophically while driving causing damage to the brake booster and lodging metal debree into the engine components. This happened at less than 100k miles on a 2020 gmc terrain.
1- at 71,000 miles in 2022 brake vacuum pump “exploded” broke into many small pieces in the middle of driving. Causing brakes to lock. Brake pedal was brick hard. Hard to maneuver the car out of traffic without causing a collision. Luckily car was not being driven at high speed. At time of repair costing $1,000 Mechanic informed me that the pump was made out of a non metal material and he could not fish the small particles out of the motor with a magnet. The motor would need to be taken apart, cleaned out and reassembled….. From this point forward the car drives in “low engine power mode” even with repairs completed and codes cleared. 2- 2 years later the same part “brake vacuum pump” exploded again. Another $1000 repair. At this time we discovered that the fine particles that were not removed from motor has now knocked the timing off by 8%. Also it has caused a knick in a seal causing an oil leak under 100k miles $1800 repair. After these extensive repairs…… The car emits gas fumes into cabin. The smell is so strong it can’t be parked in the garage because it circulates through the house. Even when car is not running. The Car can’t be driven because risk of fire or explosion from gas. Fuel system gets cleaned. Injectors replaced. The car temporarily runs without the gas smell. 2 weeks later the gas smell returns Come to find out the fuel pump failed. Search online and find there is a recall for fuel pumps in this same make model and year. But not this vin number. The car has been a headache from day 1. Recall the whole car at this point, to have so many faulty parts in such major systems of a car is crazy.
I was driving 55 miles an hour on an Expressway. And suddenly my truck just shut off.The brake became very hard unable to break very scary situation for me and my children. Engine power was reduced and would not start, many errors came up. The vacuum pump failed, which also caused the cam shafts to fail.The vacuum pump exploded into pieces and sent metal into my engine.
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.
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.
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.
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.
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.
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.
Vacuum pump went out. It was a recall, previously on older models, but this model needs to
I filed a complaint with the federal safety agency 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. the federal safety agency 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 the federal safety agency AND GM GOING TO DO WAIT UNTIL SOMEONE IS KILLED BECAUSE OF THIS ISSUE !!!!!!!!
SERVICE BRAKE ASSIST CAME ON, CHECK ENGINE LIGHT CAME ON AND VEHICLE WAS HARD TO STOP. Took to authorized service dealer and all parts were replaced. After driving it for a little while, SERVICE BRAKE ASSIST BACK ON, CHECK ENGINE LIGHT BACK ON AND VEHILCE IS HARD TO STOP.
Break assist light comes on and brakes stiffen suddenly with no warning. Happened 6 times now in a 3 year span. Gotten it "fixed" each time but it keeps happening
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!!
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 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.
GMC techs have already documented this issue could not be caused by wear and tear or lack of service - of which there is none the car has been serviced every10k miles as advised. GMC coperate has been contacted case # 71853883 The vacuum pump has failed due to MECHANICAL FAILURE causing it to explode and send pieces into the camshaft. The lack of vacuum caused complete brake failure rendering the car unsafe. GMC is aware of the issue as others habe reported it (I have proof of this) and refuses to recall the cars. The cars loose breaking in the middle of driving with no indicator lights or any other indications. The breaks had just been replaced in may - the incident occurred in October. Has not been driven since.
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.
The contact owns a 2020 GMC Terrain. The contact stated while driving 40 MPH the "Brake Assist" warning light illuminated. The contact attempted to depress the brake pedal, but the pedal was stiff. The contact was unable to depress the pedal. The vehicle was taken to a local dealer and unknown repairs were performed. The vehicle was repaired; however, recently the failure reoccurred. The contact stated that the "Brake Assist" warning light illuminated, and the brake pedal was difficult to depress. The vehicle was not taken to a dealer or an independent mechanic to be diagnosed or repaired. The manufacturer was not informed of the failure. The failure mileage was approximately 162,000.
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.
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