This service bulletin provides information on replacing the intake manifold when the engine is replaced after severe internal engine damage.
full bulletin at NHTSA ↗2018 GMC Terrain engine problems
moderate Owners of the 2018 GMC Terrain have filed 18 NHTSA complaints about the engine at roughly $3,100 to repair (U.S. federal records, as of July 2026). Source: NHTSA Office of Defects Investigation. See engine across all vehicles →
Complaints
18
Recalls
0
Avg fix
$3,100
| Model year | engine complaints |
|---|---|
| 2014 Terrain | 93 |
| 2015 Terrain | 62 |
| 2016 Terrain | 34 |
| 2017 Terrain | 57 |
| 2018 Terrain (this page) | 18 |
| 2019 Terrain | 17 |
| 2020 Terrain | 18 |
| 2021 Terrain | 4 |
| 2022 Terrain | 7 |
When does it fail?
Of the 18 engine complaints filed for the 2018 GMC Terrain, here's the actual mileage breakdown — failures cluster heaviest at 25,000-50,000 mi.
0-25k
25-50k
50-75k
75-100k
100-125k
125-150k
150k+
Each bar shows the share of total complaints filed at that mileage range. Peak failure window highlighted. Some owners report problems earlier; some make it well past 150,000 miles symptom-free. Maintenance habits and driving conditions shift the curve as much as mileage alone.
What stands out
No new NHTSA engine complaint has been filed on this vehicle in over 3 years — the issue may be aging out of the active population.
Is there a fix? Manufacturer service bulletins
The manufacturer has issued service bulletins covering engine 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.
The service bulletin advises the tech of a normal transmission shift condition and the delay in throttle response when the throttle plate is opened rapidly and advises the customer that it is normal for the delay.
full bulletin at NHTSA ↗This service bulletin provides information to dealership personnel for new vehicles with less than 1,000 miles that may not pass California smog inspection or smog inspection in other states.
full bulletin at NHTSA ↗This warranty administration bulletin provides policy information on vehicles outside of a California Emissions State who move to and register their vehicle in a California Emission State may be entitled to the 7 year, 70,000-mile Emission Select State Component Limited Warranty.
full bulletin at NHTSA ↗This bulletin advises the technician to flush the cooling system multiple times if oil has been found in the cooling system and replace the parts that may be contaminated due to oil in system.
full bulletin at NHTSA ↗Source: NHTSA manufacturer communications. Bring the bulletin number to your dealer or shop.
The failure pattern owners describe
2018 GMC Terrain owners report sudden engine shutdowns and severe power loss with little to no warning. The most common theme is stalling mid-drive—at highway speeds, in traffic, on city streets—with no check engine lights before the event. When owners do get diagnostics, vacuum pump failure tops the list, often causing secondary damage like crankshaft sensor shearing and brake system issues since vacuum pumps power brake assist. Oxygen sensor, PCV tube, and air inlet tube failures have also required replacement.
At higher mileages, catalytic converter failures and actual engine damage appear: crankshaft sensor issues, camshaft failure, broken piston lands, and complete engine seizure requiring replacement. One owner at 342,000 miles had catastrophic engine failure; another at 92,000 needed a full engine replacement. A diesel owner reported severe blowby with persistent check engine lights and warranty already expired.
The AutoStop feature draws repeated criticism—no defeat switch, hesitation and lurching in stop-and-go traffic, and customers claim it's chewing through batteries (one owner on their third). One radiator replacement claim appears questionable; the customer was denied the old parts. All shutdowns pose genuine collision risk, especially mid-traffic on highways. Owners note lack of warning lights or accessible recalls covering their specific VINs and model years.
Same GMC Terrain engine reports on nearby years: 2015 · 2016 · 2017 · 2019 · 2020
Failure modes owners describe
Vacuum pump failure
Vacuum pump cracks or fails, causing sudden engine stall with no warning lights and loss of brake assist. Secondary failures include crankshaft sensor damage and brake pedal becoming hard to engage.
When: 121,000 miles (one case); also reported at lower mileages during normal driving
Symptoms owners cite: Engine stalls without warning; No check engine light before stall; Loss of brake assist; brake pedal becomes hard to engage; Vehicle cannot be restarted or restarting fails
Repairs/costs cited: Vacuum pump replacement; one case involved crankshaft sensor shearing off and requiring replacement
Engine power reduction / stall with 'Engine Power Reduced' message
Vehicle displays 'Engine Power Reduced' or 'Low Power Mode' message and stalls during normal driving. Cause varies (oxygen sensor, PCV tube, air inlet tube issues cited in one case; full engine replacement needed in others).
When: 30,309 miles (oxygen sensor/PCV case); 92,000 miles (full engine replacement needed); also at 65 MPH highway speed
Symptoms owners cite: Dashboard message 'Engine Power Reduced'; Vehicle stalls or severely decelerates; No restart capability or limited restart; Vehicle enters neutral without driver input (one case); Brake assist failure (one case)
Codes mentioned: Service Emissions (message, not code)
Repairs/costs cited: One case: oxygen sensor, PCV tube, air inlet tube replaced ($1,460 at dealer); another case: full engine replacement recommended at 92,000 miles (not yet repaired)
Recalls/TSBs owners mention: Manufacturer notified in some cases but no assistance offered or recall applied to 2018 models (2019 recall noted but not covering 2018)
Diesel particulate filter failure
Diesel particulate filter becomes faulty and triggers 'Service Emissions' message and severe deceleration (from 65 MPH to 20 MPH).
When: 26,000 miles
Symptoms owners cite: Check engine light illuminates; 'Service Emissions' message displayed; Vehicle decelerates to 20 MPH on highway
Repairs/costs cited: Diesel particulate filter replacement required (not yet repaired at time of complaint); manufacturer would not cover under extended warranty for this VIN
Recalls/TSBs owners mention: Manufacturer notified; no assistance offered; VIN not covered under extended warranty
Catalytic converter failure
Catalytic converter fails, limiting vehicle to 5 MPH and producing persistent check engine code P1186 that dealer cannot resolve. Damages engine.
When: 101,650 miles and 5.5 years old; also reported as causing engine damage at undisclosed mileage
Symptoms owners cite: No warning light before failure; Vehicle limited to 5 MPH; Check engine light remains on after failure; Engine damage reported
Codes mentioned: P1186
Repairs/costs cited: Catalytic converter replacement needed; no replacement parts available from dealer for 2018 model (dealer states production ended); dealer inability to clear code P1186
Recalls/TSBs owners mention: Recalls issued for 2017 and 2019 models; 2018 not covered; extended warranty extended to 100,000 miles on other years but insufficient for this failure at 101,650 miles
Camshaft failure
Camshaft fails during driving, disabling vehicle on roadway. A 'Reduced Power' notice appears shortly before failure.
When: Undisclosed mileage
Symptoms owners cite: 'Reduced Power' notice on dashboard; Vehicle becomes disabled in roadway; Near-miss collision risk
Repairs/costs cited: Camshaft replacement performed by independent ASE-certified mechanic
Broken piston land and ring
Internal engine damage: piston land and ring break, forcing vehicle into limp mode during highway driving.
When: Undisclosed mileage; interstate driving
Symptoms owners cite: Vehicle enters limp mode while driving on interstate; Severe power loss
Repairs/costs cited: New engine required (full engine replacement recommended by dealer)
Complete engine failure requiring replacement
Engine fails catastrophically, necessitating full engine replacement. Occurs with little to no warning.
When: 92,000 miles; 342,000 miles (high mileage case)
Symptoms owners cite: 'Engine Power Reduced' message before stall (one case); Vehicle stalls and will not restart; No warning lights prior to failure (at least one case)
Repairs/costs cited: Full engine replacement needed (not repaired in at least one case; customer unable/unwilling to proceed with cost)
Recalls/TSBs owners mention: Manufacturer notified in one case; no assistance offered
Engine blowby (diesel model)
Excessive pressure and crankcase gases escape when oil filler cap is removed during engine running. Persistent check engine light; diesel warranty expired.
When: Undisclosed mileage; vehicle out of warranty at time of report
Symptoms owners cite: High pressure from oil filler cap when engine running; Check engine light on and will not clear; Dealer unfamiliar with diesel option; unable to diagnose
Repairs/costs cited: Outside mechanics report expensive repair costs; repair not completed at time of complaint
AutoStop feature design defect
AutoStop feature lacks a defeat switch. In stop-and-go traffic or during acceleration from a stop, engine restart hesitation and lurching create collision hazard. Contributes to premature battery failure (multiple replacements needed).
When: Recurring during traffic conditions; battery issues compound problem
Symptoms owners cite: Hesitation when accelerating from stop after AutoStop restart; Lurching forward after hesitation, risking collision with vehicle ahead; Premature battery drain and failure (one owner on third battery); Loss of engine response in heavy traffic; Vehicle shutdown even with AC on high (hot climates)
Repairs/costs cited: Dealer cannot or will not provide software defeat or hardware modification; customer requested but denied
Recalls/TSBs owners mention: No response from manufacturer on this issue; competitors' AutoStop systems include defeat switch
Synthesized from 18 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 4 most recent
The dealer has not been very familiar with the diesel option in this vehicle. Dealer has found nothing wrong with the engine in this regard. Now the car is out of warranty and will be very expensive to fix according to outside mechanics. The car is experiencing severe BLOW-BY When the oil filler cap is removed while the engine is running, the pressure coming out of the engine is very high. I…
Catalytic converter failed when driving damaging the engine. Vehicle undrivable and waited for repair at shop for over 90 days. Engine warning light keeps coming on with error code P1186 that the GMC dealer can not fix.
Beaverton GMC did repair work on my vehicle. During the inspection they said they found the radiator leaking from a number of spots and it needed replaced. It has never leaked and did not need replaced. Why did they do it? I as for the parts but they tossed them and would not give them to me.
The contact owns a 2018 GMC Terrain. The contact stated while driving at approximately 65 MPH, the check engine warning light illuminated, and the vehicle decelerated to 20 MPH. Additionally, the message "Service Emissions" was displayed. The vehicle was taken to the local dealer who diagnosed that the diesel particulate filter was faulty and needed to be replaced. The vehicle was not yet…
Had engine 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 engine problem on the 2018 GMC Terrain?
It's a documented issue but not catastrophic. 18 complaints have been filed. Repairs average $3,100 and most owners catch it before it causes a breakdown.
At what mileage does the engine typically fail?
Based on the 18 complaints filed, engine issues most often appear around 145,250 miles. Some report problems earlier; some make it well past 150,000 with no symptoms. Maintenance habits matter — vehicles that received timely fluid services and were not regularly overworked tend to last longer.
What does it cost to fix?
Independent shops typically charge around $3,100 for engine 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 engine?
No active recalls currently cover engine 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.