This preliminary informational (PI) bulletin provides information to dealership personnel that may be helpful when addressing underbody component corrosion with customers.
full bulletin at NHTSA ↗2018 GMC Terrain powertrain problems
moderate Owners of the 2018 GMC Terrain have filed 39 NHTSA complaints about the powertrain, typically surfacing around 10,300 miles at roughly $2,500 to repair (U.S. federal records, as of July 2026). Source: NHTSA Office of Defects Investigation. See powertrain across all vehicles →
Failure mileage
Complaints
39
Recalls
0
Avg fix
$2,500
| Model year | powertrain complaints |
|---|---|
| 2014 Terrain | 33 |
| 2015 Terrain | 21 |
| 2016 Terrain | 10 |
| 2017 Terrain | 23 |
| 2018 Terrain (this page) | 39 |
| 2019 Terrain | 49 |
| 2020 Terrain | 23 |
| 2021 Terrain | 7 |
| 2022 Terrain | 8 |
1crash
What stands out
Owners have filed 39 powertrain complaints with NHTSA against this vehicle, but no formal recall covers the issue — the federal record reflects what manufacturers have admitted, not everything owners are reporting.
Powertrain accounts for 18% of all owner complaints filed against this vehicle, across 7 categories tracked.
Is there a fix? Manufacturer service bulletins
The manufacturer has issued service bulletins covering powertrain on this vehicle — documented repair instructions, service campaigns, or warranty extensions sent to dealers. A TSB isn't a recall (it's not a free safety remedy), but it's the manufacturer acknowledging the issue and how to fix it.
This bulletin provides information on identifying Non-GM Engine Calibrations for Gasoline Engines using the Tech 2 or GDS 2.
full bulletin at NHTSA ↗This service bulletin provides information on the harmful effects of ethylene glycol in transmission fluid.
full bulletin at NHTSA ↗This service bulletin provides 9th gear operation information to respond to customers that may comment on transmission shift operation.
full bulletin at NHTSA ↗This service bulletin advises the tech that the rotational Clicking Noise Heard After Engine Shut Down may be normal characteristics of the vehicle.
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
The 2018 GMC Terrain powertrain complaints center on a cluster of intermittent but recurring failures that mechanics repeatedly cannot fix. The most common issue is a repeating P0171 code (system too lean) that returns monthly despite brake pump replacement, intake hose reseating, mass air flow sensor swaps, and fuel system cleaning—one owner has dealt with this since March 2024. A second set of complaints involves transmission problems ranging from refusal to shift into gear, sudden jerks that throw the steering wheel hard left or right, limp-mode activation capping speed at 30 mph, and complete loss of all gears leaving owners stranded. Vacuum pumps are failing without warning at low mileage (68,000 miles noted) and either seizing or bursting into pieces that contaminate engine oil—dealers are denying warranty coverage because the pump failure itself becomes the "cause." Loss of propulsion at highway speeds, engine stalling during acceleration, and timing chain failures also appear. Owners report multiple dealer visits, ECM replacements, fuel injector swaps, and computer reflashes that do not address root causes. GMC's own engineers have been unable to diagnose some problems, and dealerships have told owners they have no solution and cannot help further.
Same GMC Terrain powertrain reports on nearby years: 2015 · 2017 · 2019 · 2020
Failure modes owners describe
Check Engine Light & P0171 Code (System Too Lean)
Check engine light triggers repeatedly with P0171 code. Owners report the code appearing after air filter replacement, low fuel tank situations, or fuel fill-ups. Mechanics have replaced brake vacuum pumps, intake hoses, mass air flow sensors, and recommended fuel system cleaners and injector additives, with no permanent resolution. One owner had the same issue since March 2024 with multiple recurrences monthly.
When: Intermittent; March 2024 onwards for one owner; often when fuel below 1/2 tank or immediately after fill-up
Symptoms owners cite: Check engine light illuminates intermittently; Code P0171 diagnosed; Engine power reduced warning message on dash; Vehicle shaking and jerking upon acceleration; Difficulty accelerating on interstate
Codes mentioned: P0171
Repairs/costs cited: Brake vacuum pump replaced; intake hose reseated; mass air flow sensor suggested; fuel system cleaned twice; fuel injector additive tried; no permanent fix achieved
Mass Air Flow Sensor & P1101 Code
Code P1101 appears when fuel tank runs low. GMC dealership initially attributed the problem to a loose tape on the sensor, which owner disputes as unreasonable. Multiple independent mechanics confirmed mass air flow sensor replacement did not resolve the issue. Owner reports many other customers with the same problem but no solution provided by GMC.
When: When fuel tank empties; documented since 2020
Symptoms owners cite: Engine light comes on when gas runs low; Code P1101 diagnosed; Problem persists despite mass air flow sensor replacement
Codes mentioned: P1101
Repairs/costs cited: Mass air flow sensor replaced without resolution; GMC charged $120 for diagnostic research
Recalls/TSBs owners mention: GMC contact named Kevin called owner and stated he was unable to reach dealerships for support
Vacuum Pump Failure
Vacuum pump seizes or fails without warning, causing loss of brake assist and engine damage. One owner lost brakes while traveling 60 mph; another's pump seized at 68,000 miles, spinning the camshaft phase actuator locating pin. Multiple owners report metal debris in oil after pump failure, with dealers refusing warranty coverage citing the pump failure as cause.
When: April 2025 and September 2025 (one owner); 68,000 miles (another owner); one incident documented April 2025
Symptoms owners cite: Loss of brake assist at highway speeds; Reduced engine power warning light; Metal shavings found in engine oil; Camshaft damage resulting from pump failure; Engine complete failure
Repairs/costs cited: Vacuum pump replacement at $3,500 (partial repair), later determined entire engine replacement needed at $12,000; warranty denied due to pump failure; dealership suggested flushing metal from engine without engine replacement
Recalls/TSBs owners mention: Warranty representative stated they receive frequent calls for these vehicles needing repairs
Transmission Shift Hesitation & Jerking
Transmission revs but delays shifting into gear, then abruptly jerks hard into gear, causing steering wheel jerk. Affects low-speed acceleration, parking lot maneuvers, and traffic situations. Occurs with and without warning codes. One owner collided with a parked vehicle due to sudden hard jerk into gear after the transmission refused to shift.
When: Various; one incident documented 9/8/2020 at 18 mph; ongoing since vehicle purchase for some owners
Symptoms owners cite: Engine revs without shifting; Delay in gear engagement; Hard jerking into gear causing steering wheel jerk; Left or right steering wheel jerk upon shift; Vehicle feels like it downshifts unexpectedly; Engine RPM jumps inappropriately
Repairs/costs cited: One owner caused $6,000 damage to own vehicle and totaled a 2010 Corolla; GMC refused to acknowledge fault
Transmission Inability to Shift / Limp Mode Activation
Transmission refuses to shift into gear or shifts into unintended gear (e.g., Park while driving). Vehicle displays 'Transmission Unable to Shift' messages, goes into limp mode limiting speed to 30 mph, or displays 'Vehicle Unsafe to Drive' warnings. Multiple owners report needing to turn vehicle off and restart to regain propulsion. At low speeds after stops, vehicle jerks and shakes upon acceleration.
When: Low speeds, after stops, traffic situations; one incident at 40 mph; another while stopped at traffic light; multiple instances over time for individual owners
Symptoms owners cite: Transmission unable to engage gear; Unexpected shift into Park during operation; Limp mode activation reducing speed to 30 mph; Speed reduction warnings on dashboard; Vehicle jerks and shakes at low speeds; No gear options available after shift to Park; Loss of propulsion despite engine running; Need to restart engine to regain propulsion; Hard shift between gears; Transmission slips out of gear into neutral then back into gear
Codes mentioned: P0700, P171D, P187D, U0422-00
Repairs/costs cited: Tow truck unable to put vehicle in Neutral; vehicle had to be dragged onto and off tow truck; dealership service for transmission, Stabilitrak, and parking assist did not resolve jerking and stalling after pickup; transmission replacement attempted but reoccurred with used replacement
Recalls/TSBs owners mention: Dealer stated transmission slipping is normal per GMC bulletin; no fixes found after multiple dealer visits
Loss of Propulsion at Highway Speeds
Vehicle loses power while driving at highway speeds on hills or during acceleration, with speed dropping from highway speed to 5-10 mph or complete loss of forward motion. Vehicle stalls or fails to accelerate despite throttle input. Occurs on downslopes and when attempting to merge or climb hills. One owner stranded 90 miles away; another had to reverse and get running start to climb small grade.
When: Highway driving; downslopes; hill climbs; one incident 11/23/2018; various speeds 25-60 mph
Symptoms owners cite: Sudden loss of power while accelerating; Vehicle stalls on downslopes and hills; Speed drops from 40-60 mph to 5-10 mph; No response to throttle input; Vehicle will not accelerate beyond 10-15 mph; Loud noises and burning smell accompanying loss of power; System lights and gauges flickering off and on; Stabilitrak and Transmission lights illuminate with loss of power
Repairs/costs cited: Dealer unable to diagnose; loose wires and minor adjustments performed at one dealership without resolving issue
Recalls/TSBs owners mention: GM OnStar advised loss of power possible but vehicle could travel onward; dealer unable to find service bulletins
Transmission Failure / Complete Loss of Gears
Transmission fails completely with no warning, leaving vehicle unable to move in any direction. Owner loses all gear options (Drive, Reverse, Neutral). Vehicle used transmission replaced but failure reoccurred immediately. Turbine shaft in transmission broke without warning. One failure at 53,000 miles on replacement transmission; another at 245,000 miles.
When: 53,000 miles (replacement transmission); 10,000 miles (one failure); 245,000 miles (another failure); very low mileage ranging from 4,200 to 53,000 for some incidents
Symptoms owners cite: Complete transmission failure; No forward or reverse motion possible; Unable to shift into any gear; Unable to shift into Neutral; Turbine shaft breaks inside transmission; Vehicle immobilized without warning; Service Transmission Soon message displayed prior to failure
Repairs/costs cited: Transmission replacement attempted with used transmission, but failure reoccurred and vehicle still not repaired; broken turbine shaft discovered upon disassembly
Engine Stalling & Intermittent Propulsion Loss
Engine stalls intermittently during acceleration, deceleration, or normal driving. Vehicle stutters, jerks, and makes unusual noises (vacuum cleaner sound). Stalling accompanied by check engine light. Affects low-speed acceleration (25-30 mph) and causes vehicle to jerk between 2,000-3,000 RPM. Multiple dealer visits, ECM replacement, fuel injector replacements, and computer updates have not resolved the issue.
When: Intermittently during driving; since November 2018 for one owner with purchase in September 2018; at various speeds from 25-55+ mph; daily occurrences for some
Symptoms owners cite: Engine stalls without warning; Stuttering and jerking during acceleration and deceleration; Unusual vacuum-cleaner-like noise during stalling; Check engine light illuminates during stalls; Hard jerking shifts between 2,000-3,000 RPM; Vehicle attempts to stall but does not fully stall; Stalling at low speeds when accelerating from stops; Engine jerks/hops when speed reaches 55 mph or higher
Codes mentioned: P0171
Repairs/costs cited: ECM replaced; multiple fuel injectors replaced; multiple computer updates performed; fuel system serviced; no permanent resolution; dealership unable to fix after multiple visits
Recalls/TSBs owners mention: GM engineers involved but unable to identify or fix problem; dealership told owner they cannot do anything else and owner forced to accept unsafe condition
Driveshaft Detachment
Driveshaft detaches from suspension and hangs down from vehicle during 4WD operation. Accompanied by abnormal grinding sound that increases in frequency. Discovered at 160,000 miles by owner during vehicle inspection. Associated with recall 17V516000 but owner's VIN not included in recall list.
When: 160,000 miles
Symptoms owners cite: Abnormal grinding sound during 4WD transition; Driveshaft hangs down from suspension; Grinding sound becomes more frequent with continued 4WD shifting
Repairs/costs cited: Vehicle not repaired; independent mechanic associated failure with NHTSA Campaign 17V516000
Recalls/TSBs owners mention: Recall 17V516000 exists but owner's VIN not included in recall list
Vacuum Pump Failure with Oil Contamination
Vacuum pump leaks and bursts into small pieces that contaminate engine oil. Owner immediately parked vehicle upon identifying leak. Pump found disintegrated when removed for replacement.
When: No mileage or timing data provided
Symptoms owners cite: Vacuum pump leaking; Vacuum pump bursts into small pieces; Oil contamination from pump debris
Repairs/costs cited: Vacuum pump replacement required; debris found in engine
Transmission Downshift Delay
Transmission fails to downshift after accelerating in traffic, maintaining excessively high RPM at lower speeds. RPM stays at 2,200 instead of dropping to proper 1,200 RPM at 40 mph, persisting for over a mile.
When: Traffic situations at 40 mph
Symptoms owners cite: Transmission remains in high gear at low speed; RPM elevated at 2,200 when should be 1,200; Prolonged high RPM operation for over one mile
Timing Chain Failure
Timing chain failed without warning due to poor design. Owner notes that GM addressed this issue in Europe by installing a plate behind the tensioner, but this part is not available in the US market.
When: No specific mileage or timing provided
Symptoms owners cite: Timing chain failure without warning
Recalls/TSBs owners mention: GM fixed issue in Europe with tensioner plate not available in US
Oil Leaks
Vehicle leaks oil (type unidentified by owner) visible as accumulation on driveway. Oil change and filter replacement did not resolve leak, suggesting O-ring or seal issue.
When: No specific timing or mileage provided
Symptoms owners cite: Oil leaking from vehicle; Accumulation on driveway
Repairs/costs cited: Motor oil and filter changed; leak persists
Automatic Braking System Lockup
Automatic braking system locked up while driving on highway, causing vehicle to stop and become immobilized.
When: Highway driving
Symptoms owners cite: Automatic braking system locked up; Vehicle unable to move
Transmission Hot & Idle Engine Alerts
Vehicle displays 'Transmission Hot Idle Engine' alerts during normal driving in low-speed residential areas. Transmission does not feel like it is shifting correctly, and owner can feel and hear the shift changes. Alert appears consistently despite dealer finding no codes.
When: 25 mph residential speeds; consistently
Symptoms owners cite: Transmission Hot Idle Engine alert displayed; Improper transmission shifting feel and sound; Hard transmission shift feeling
Repairs/costs cited: Dealer visit showed no codes
Synthesized from 39 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 1 most recent
While driving in the rain at about 25-30 mph I noticed a loss of propulsion and before I could turn off the main road the vehicle came to a rolling stop and would not recognize any gears. causing us to block the roadway and had to have it towed home. Took to local car dealer they said it RDCCM abnormal errors like u0422-00 and brake control module errors. Further diagnostics were need to figure…
Had powertrain trouble with your 2018 GMC Terrain?
File a complaint with NHTSA → It's free, official, and how every report above got here — owner filings are the federal safety record this page is built on.
Common questions
How serious is the powertrain problem on the 2018 GMC Terrain?
It's a documented issue but not catastrophic. 39 complaints have been filed. Repairs average $2,500 and most owners catch it before it causes a breakdown.
At what mileage does the powertrain typically fail?
Across the 21 complaints that reported odometer mileage, most powertrain failures cluster between 3,000 and 53,000 miles, with the median around 10,300. A quarter of owners report trouble before 3,000; a quarter make it past 53,000. Maintenance history matters more than the odometer alone — this is the reported failure window, not a guarantee.
What does it cost to fix?
Independent shops typically charge around $2,500 for powertrain repairs on this vehicle. Dealer pricing tends to run 20-40% higher. The exact figure depends on the specific failure mode, parts availability, and your local labor rates. If you're outside factory warranty, an extended service contract often covers this category.
Are there any recalls related to powertrain?
No active recalls currently cover powertrain issues on this vehicle. The complaints filed represent owner-reported failures that haven't risen to the level of a manufacturer-issued recall — but they're still worth knowing about before you buy or budget for repairs.
Related
Complaint and recall data sourced from the National Highway Traffic Safety Administration (NHTSA)
public records database. Verify the raw federal record at
nhtsa.gov/vehicle/2018/GMC/Terrain.
Severity ratings are derived from reported crashes, fires, injuries, and fatalities. Repair cost estimates are
independent-shop national averages and may differ in your area. Some links on this page are affiliate links.