2020 GMC Terrain

While driving my 2020 GMC Terrain, I experienced a sudden loss of normal braking assistance. I had been traveling on the highway and exited onto a main road. As I approached a red traffic light at approximately 50 mph and attempted to brake, the vehicle would not stop normally. I was unable to stop for the red light and went through the intersection before I was able to safely get the vehicle off the roadway. Fortunately, there was no vehicle directly in front of me and I was able to make it through the intersection before any other cars, so no collision occurred. The vehicle was subsequently inspected and diagnosed by a GMC dealership. A diagnostic scan performed after the incident showed code P0556 for the brake booster pressure sensor circuit range/performance. The GMC dealership later diagnosed problems involving the vacuum pump, exhaust camshaft, and timing components and recommended replacement of the vacuum pump, exhaust camshaft, timing components, and related parts.” The sudden loss of braking assistance created a serious safety hazard and could have resulted in a collision, serious injury, or death. The vehicle is currently available for inspection.

NHTSA ID

11766529

Incident

Aug 29, 2026

Having the start stop issue on my terrain and recently over the last few months, it has been using oil everything that sounds exactly like the recall but mine is not included. My start stop is not working and I have to get him since it had only 60,000 miles on it years ago, but nothing was done.

NHTSA ID

11762749

Incident

Dec 17, 2021

Fuel pump control module and or the in tank fuel pump failed and or isn’t making proper connection for car to run correctly. Safety was put at risk as car came to abrupt halt while driving. Driver was outside of vehicle at busy intersection for vehicle diagnostics and battery jump. Battery was removed and new battery installed yet problem persists. Not confirmed by dealer but code is as follows (p129F). Maintenance performed by owner;Code reader used for diagnostics, new battery installed. Problem persists. Car started, drove and stumbled to then die. Check engine now displays.

NHTSA ID

11761691

Incident

Sep 2, 2026

The contact owns a 2020 GMC Terrain. The contact stated that while driving at an undisclosed speed, the vehicle failed to stop as intended. The brake pedal was depressed to the floor, and the vehicle slowed down and eventually stopped. The vehicle was taken to an independent mechanic, where it was diagnosed with a failed vacuum pump. The mechanic informed the contact that the vacuum pump needed to be replaced. The vehicle was repaired. The contact stated that the failure was a known issue with the vehicle. The manufacturer was not notified of the failure. The failure mileage was approximately 92,000.

NHTSA ID

11760902

Incident

Aug 24, 2026

Mileage

92,000 mi

COMPONENT OR SYSTEM FAILED - GMC Dealership replacing fuel pump. SAFETY OR SAFETY OF OTHERS AT RISK - stalled in remote area with no internet/cell service. In order to get to safety we travelled 13 miles of narrow 2 lane roads with no shoulder or escape areas. Road included 3 miles of a steep downhill grade. HAS THE PROBLEM BEEN REPRODUCED OR CONFIRMED BY A DEALER - Yes, Walser GMC [XXX] WERE THERE ANY WARNING LAMPS, MESSAGES OR OTHER SYMPTOMS OF THE PROBLEM PRIOR TO THE FAILURE - No, drove 400 miles w/2 stops, rest stop and lunch/gas. Got to our destination, shut off the car. Needed to move the vehicle to designated parking spot and at first the vehicle would not start, got it started but lurched forward, engine chugged, no acceleration and then stalled. Waited 10 minutes vehicle started with same symptoms but became drivable so we headed to safety 13 mile to nearest town, [XXX]. The area has recently been battling forest fires and in our area, although "safe", there was still HIGH fire danger. We did not feel safe w/o a vehicle for (possible) rapid escape. The city has limited services, no rental car company, no Uber/Lift, closest car dealership 90 miles away. Vacation cancelled. Hired North [XXX] Towing to transport vehicle and people 300 miles to Walser [XXX], [XXX]. Family member drove us to our home in [XXX]. To date vehicle mileage - 30,000 miles! INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

NHTSA ID

11759075

Incident

Aug 19, 2026

The brake suddenly became impossible to depress more than 3/4 of an inch. Almost unable to stop nearly hitting another vehicle. The dashboard then lit up with a "service brake system" warning. Luckily was only a few minutes from home brought it home and began the search for the issue. The brake vacuum pump failed. Unsure of further damage at this point. It being Sunday am unable to contact a shop or dealer.

NHTSA ID

11758896

Incident

Aug 23, 2026

While driving, I suddenly smelled something burning. Immediately after, a warning popped up stating 'Engine power is reducing,' the check engine light came on, and I experienced a sudden, near-total loss of power braking assist, making the brake pedal extremely hard to press. I had to use intense force to bring the vehicle to a stop. A scan of the vehicle's OBD-II codes revealed codes P0556 (Brake Booster Pressure Sensor Circuit), P0014 (Exhaust Camshaft Position Timing Over-Advanced), and P0017 (Crankshaft Position - Camshaft Position Correlation). This is a known failure where the engine-driven mechanical brake vacuum pump seizes up, destroys the braking vacuum assist, and bends or shifts the exhaust camshaft reluctor wheel, causing a severe and immediate safety hazard while in motion.

NHTSA ID

11757862

Incident

Aug 19, 2026

During heavy rain, the sunroof on my Terrain leaked badly enough to allow a substantial amount of water into the vehicle. The rear floor area became completely saturated, and the sunroof controls stopped working. I brought the vehicle to Hudson Cadillac Buick GMC in Poughkeepsie, New York, to have the problem diagnosed and repaired. The resulting repairs and water-damage cleanup cost me nearly $3,000 out of pocket. I was advised that the damage was not covered by my warranty or by my insurance. What concerns me most, however, is that this does not appear to have been an isolated incident. While my Terrain was at the dealership, I learned that four other GMC Terrains were also at the dealership experiencing water damage related to leaking sunroofs. Mine was the fifth. Finding five Terrains at the same dealership with what appeared to be similar water-intrusion problems was extremely concerning to me and made me question whether this is a recurring issue with these vehicles. I also have a video provided by the dealership documenting the water damage to my vehicle, and I am happy to provide that video, my repair invoice, photographs, or any other documentation you would like to review. They went to great lengths to dry the vehicle, which was especially important to me because I was extremely concerned about hidden moisture and dangerous mold. Thankfully, after their work, there is no odor and no indication of remaining moisture or mold, and I am very satisfied with the quality of the repair and cleanup. The extent of the water damage was frightening. At one point, I was genuinely concerned that I might have to get rid of the vehicle simply because I was afraid of the long-term consequences of having so much water inside it. I am very grateful that the dealership was able to restore the vehicle so thoroughly but there is still a possibility that the repair will fail and I will have to replace the sunroof module.

NHTSA ID

11756698

Incident

Aug 6, 2026

This preliminary information advises a dealer on how to email GDS2 session logs into Technical Assistance.

PI to help diagnose A/C concern

This preliminary information communicates information about how to determine if a wheel and tires size change is available.

This preliminary information discusses a condition that may arise from the drivers window switch sending an errant message causing the vehicle to enter manual fob learn mode.

This preliminary information advises a dealer on how to email GDS2 session logs into Technical Assistance.

This Preliminary information communicates the steps on how to save a GDS2 Session Log and upload to a Technical Assistance Case in CX Connect.