According to Au7o's analysis of 740+ owner reports, the 2018 GMC Terrain has 8 documented known issues, with 4 rated critical. The most serious are 1.5L Turbo PCV System Failure and Coolant/Oil Intrusion ($400-$2,800 repair), Start/Stop Transmission Accumulator Endcap Missing Bolts - Fluid Leak & Loss of Propulsion (Recall), Engine-Driven Brake Vacuum Pump Failure - Sudden Loss of Power Brake Assist (Hard Pedal) ($400-$1,500 repair) and Charge Air Cooler Outlet Duct Disconnecting at the Throttle Body - Sudden Power Loss and Stall ($0-$250 repair). The most commonly reported issue is 1.5L Turbo PCV System Failure and Coolant/Oil Intrusion with 740 owner reports. Across all issues with published estimates, repair costs range from $100 to $2,800. DIY maintenance guides at au7o.io.
On the 2018-2025 GMC Terrain, the 2018+ Terrain with the 1.5L turbocharged engine (LFV/LYX) experiences PCV (Positive Crankcase Ventilation) diaphragm failure inside the valve cover. The integrated PCV diaphragm tears, causing excessive crankcase pressure that forces oil into the intake manifold and intercooler. Symptoms include oily residue around the air intake and intercooler outlet pipe. In severe cases, excessive crankcase pressure also causes coolant intrusion into the combustion chamber. GM issued TSB PIT5697 for this issue. This is the same problem affecting the Chevrolet Equinox 1.5T of the same era.
Oil residue in intercooler outlet pipe or air intake
Blue/white smoke from exhaust
Coolant level dropping with no visible external leak
Rough idle after cold start
Check engine light (boost, MAF, or misfire codes)
Oil smell from engine bay
How to Fix
Replace valve cover assembly with updated GM part (GM 12690058) which includes the revised PCV diaphragm. Clean intercooler and intake manifold of oil contamination. Check for coolant consumption alongside oil intrusion. Inspect air-to-water intercooler for coolant contamination — replacement if contaminated (GM 84446987).
High Confidence740 owner reportsLast reported by owners Feb 2026Reviewed Feb 2026
On the 2018-2022 GMC Terrain 1.5L I4 turbo (LYX), on 1.5L LYX-equipped Terrains the charge air cooler outlet tube can separate from the throttle body inlet. The retaining clip design does not hold the duct under boost pressure and heat cycling, so the tube pops off, dumping boost and unmetered air. GM issued Service Update N192266090 covering the charge air cooler duct disconnect at the throttle body on 2019 Malibu, Equinox and Terrain 1.5L vehicles, and the condition is further covered by field bulletins PIP5651 and 22-NA-224 across the 2018-2022 range. This is separate from the frozen-CAC condition: the cooler is fine, the connection has come apart. It is also distinct from the throttle body / TPS electrical failure already documented, because the fault is mechanical air-path separation.
Inspect the outlet duct and throttle-body connection, reseat the duct and install the improved retainer when the duct and sealing surfaces remain serviceable. Replace a damaged duct rather than relying on the clip alone, and use the free service update when the VIN qualifies.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
2018-2022 GMC Terrain 1.5L turbo branch covered by the service procedure. The OEM catalog also lists the 1.6L diesel, but this issue record is the LYX 1.5L; inspect the duct before ordering.
On the 2018-2024 GMC Terrain, on the second-generation Terrain (2018+) with the turbocharged 1.5L LYX or 2.0L LTG engine, the air-to-air charge air cooler (intercooler) accumulates condensate from humid or rainy driving plus PCV-borne moisture. In cold ambient temperatures that water freezes inside the CAC core, restricting charge airflow. GM documents this in service bulletin 18-NA-020, originally issued for 2018-2022 and later expanded through the 2024 model year. Owners on the Terrain/Equinox forum describe ice and standing water inside the charge tube. This is a distinct failure from the CAC outlet duct popping off the throttle body and from the 1.5L PCV coolant/oil intrusion problem - here the cooler itself is obstructed by ice or contamination, not disconnected.
Follow 18-NA-020: leak-test the CAC, thaw and clean a non-leaking contaminated cooler, and install only the bulletin-specified thermostatic shutter for the confirmed RPO and cold-weather branch. A universal intercooler or grille insert is not the prescribed repair.
On the 2018-2022 GMC Terrain, on second-generation Terrains (2018-2022) with the 1.5L LYX and 2.0L LTG turbo engines, the camshaft-driven mechanical vacuum pump that supplies the brake booster can fail suddenly and without warning. When it fails, drivers lose power brake assist and the pedal becomes hard as a rock, requiring dramatically increased effort to stop and greatly increasing crash risk. In severe cases pump internals disintegrate and send metal debris into the engine oil, contaminating internal components and turning a brake repair into a costly engine job. The defect is the subject of a February 18, 2026 proposed federal class-action (Thieme, Gill, Morley v. General Motors, LLC, E.D. Michigan) covering 2018-2022 Equinox/Terrain and 2016-2020 Buick Envision; the suit alleges GM knew of the issue as early as a March 2017 stop-delivery order. No recall has been issued as of mid-2026.
Brake pedal suddenly hard/stiff and difficult to press
Loss of power brake assist
Longer stopping distances
Whining or knocking noise from front of engine
Metal shavings in engine oil in severe cases
How to Fix
Replace the failed camshaft-driven vacuum pump (and the brake booster if it was damaged). If the pump disintegrated, an oil-system flush and inspection for metal contamination is required; catastrophic cases need internal engine repair. With no recall issued, repairs are typically owner-paid unless covered by powertrain warranty or resolved through the pending class action.
On the 2010-2024 GMC Terrain, terrain front and rear hub assemblies integrate the ABS magnetic encoder ring into the bearing's inboard seal, where it sits directly exposed to road salt and moisture. Two distinct failure modes result. The mechanical one is the familiar humming or roaring that rises with speed and changes when loading the bearing in a wide turn. The one that fools owners and shops is encoder-ring failure on a bearing that is still mechanically tight and silent: the wheel speed signal drops out and the vehicle sets a wheel speed sensor code with ABS, traction control and stability control disabled. Replacing only the external sensor does not fix it, because the encoder is part of the bearing. Both generations are affected, with salt-belt vehicles failing earliest.
ABS, traction control and stability control warning lights
Speedometer dropout or erratic reading
No noise or play but a wheel speed sensor code present
How to Fix
Compare all four live wheel-speed signals and inspect the harness before choosing a hub. Front/rear, driven/non-driven and 2010-2017 versus 2018-2024 assemblies differ, so the broad issue cannot safely point to one hub.
On the 2018-2020 GMC Terrain, nHTSA campaign 20V668 covers certain 2018-2020 GMC Terrain vehicles. Missing bolts on the transmission start/stop accumulator endcap can cause a transmission-fluid leak, loss of propulsion and possible fire.
On the 2018-2022 GMC Terrain, second-generation Terrains with the electronic precision (push-button/monostable) shifter throw a persistent "Shift to Park" warning and refuse to shift out of (or fully into) park even when correctly positioned. GM traced it to build-up/contamination on the Park switch contacts in the transmission control (shifter) assembly, causing high resistance so the BCM cannot electronically confirm the Park position. It can strand the vehicle and, in many cases, keeps the ignition from turning off (stuck in Accessory).
GM issued field actions ranging from an ECM/BCM software update to a shifter wire-harness/jumper change and ultimately replacement of the shifter control (transmission control button) assembly. Dealers first clear the fault; recurring cases get a new shifter cartridge or full center-console shifter unit.
On the 2013-2019 GMC Terrain, the IntelliLink/MyLink touchscreen freezes and spontaneously reboots, losing control of radio, climate, navigation and Bluetooth, and often displays a black screen or a frozen backup-camera image. During a reboot, phone calls drop and the rear camera can go dark while in reverse - a visibility concern. Root causes include software glitches, outdated firmware, and occasionally loose display/camera wiring.
Start with a software/firmware update at the dealer and a system reset (Home + Fast Forward held ~10s, or Return to Factory Settings). Persistent cases require reseating/repairing loose harness connectors or replacing the radio/display module or backup camera.
General Motors, LLC (GM) is recalling certain 2024 Chevrolet Blazer, Blazer EV, Equinox, and GMC Terrain vehicles. The door strikers may fracture, resulting in the door opening unexpectedly.
Campaign #23V86900021/12/2023
AIR BAGS:SENSOR:OCCUPANT CLASSIFICATION:FRONT PASSENGER
General Motors, LLC (GM) is recalling certain 2023 Chevrolet Equinox and GMC Terrain vehicles equipped with ventilated front passenger seats. The Occupant Classification System may not properly disable the front passenger air bag when there is a small child or child restraint detected in the seat.
Campaign #22V92900015/12/2022
CHILD SEAT:VEHICLE LATCH ANCHOR
General Motors, LLC (GM) is recalling certain 2020-2023 Chevrolet Equinox and GMC Terrain vehicles. The four rear-seat lower child seat LATCH anchorage bars may have excessive powder coating, which could prevent a child seat from being installed with the anchorage bars. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard number 225, "Child Restraint Anchorage Systems."
Campaign #23V33900011/05/2023
SEATS
General Motors, LLC (GM) is recalling certain 2022-2023 Chevrolet Equinox and 2022 GMC Terrain vehicles. The driver's seat may have a stripped or loose bolt at the seat frame height-adjust pivot.
Campaign #22V72400029/09/2022
TIRES
General Motors, LLC (GM) is recalling certain 2021-2022 Chevrolet Equinox and GMC Terrain vehicles equipped with certain Hankook tires. The tires may have been manufactured with an insufficient amount of curative agent, which could cause tread separation.
Campaign #21V61200005/08/2021
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According to Au7o's analysis of 740+ owner reports, the 2018 GMC Terrain has 8 documented issues. The most frequently reported are: 1.5L Turbo PCV System Failure and Coolant/Oil Intrusion, Start/Stop Transmission Accumulator Endcap Missing Bolts - Fluid Leak & Loss of Propulsion (Recall), Engine-Driven Brake Vacuum Pump Failure - Sudden Loss of Power Brake Assist (Hard Pedal). Of these, 4 are rated critical and should be addressed promptly.
Is the GMC Terrain reliable?
The 2018 GMC Terrain has 8 known issues documented across 740+ owner reports. 4 issues are rated critical: 1.5L Turbo PCV System Failure and Coolant/Oil Intrusion and Start/Stop Transmission Accumulator Endcap Missing Bolts - Fluid Leak & Loss of Propulsion (Recall) and Engine-Driven Brake Vacuum Pump Failure - Sudden Loss of Power Brake Assist (Hard Pedal) and Charge Air Cooler Outlet Duct Disconnecting at the Throttle Body - Sudden Power Loss and Stall. Prospective buyers should inspect for these issues and factor potential repair costs into their purchase decision. Regular maintenance following the manufacturer's schedule helps prevent many common problems.
How much does it cost to fix common GMC Terrain problems?
Repair costs for known GMC Terrain issues range from $0 to $2,800, depending on the specific problem and whether you choose DIY or professional repair. The most critical issue, 1.5L Turbo PCV System Failure and Coolant/Oil Intrusion, typically costs $400-$2,800 to repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.
What is the 2018-2025 GMC Terrain 1.5L Turbo PCV System Failure and Coolant/Oil Intrusion?
The 2018+ Terrain with the 1.5L turbocharged engine (LFV/LYX) experiences PCV (Positive Crankcase Ventilation) diaphragm failure inside the valve cover. The integrated PCV diaphragm tears, causing excessive crankcase pressure that forces oil into the intake manifold and intercool… Repairs typically run $400-$2,800. Severity: high.
What is the 2018-2020 GMC Terrain Start/Stop Transmission Accumulator Endcap Missing Bolts - Fluid Leak & Loss of Propulsion (Recall)?
NHTSA campaign 20V668 covers certain 2018-2020 GMC Terrain vehicles. Missing bolts on the transmission start/stop accumulator endcap can cause a transmission-fluid leak, loss of propulsion and possible fire. Severity: high.
What is the 2018-2022 GMC Terrain Engine-Driven Brake Vacuum Pump Failure - Sudden Loss of Power Brake Assist (Hard Pedal)?
On second-generation Terrains (2018-2022) with the 1.5L LYX and 2.0L LTG turbo engines, the camshaft-driven mechanical vacuum pump that supplies the brake booster can fail suddenly and without warning. When it fails, drivers lose power brake assist and the pedal becomes hard as a… Repairs typically run $400-$1,500. Severity: high.
What is the 2018-2022 GMC Terrain Charge Air Cooler Outlet Duct Disconnecting at the Throttle Body - Sudden Power Loss and Stall?
On 1.5L LYX-equipped Terrains the charge air cooler outlet tube can separate from the throttle body inlet. The retaining clip design does not hold the duct under boost pressure and heat cycling, so the tube pops off, dumping boost and unmetered air. GM issued Service Update N1922… Repairs typically run $0-$250. Severity: high.
What is the 2018-2022 GMC Terrain Electronic Shifter Fault - Vehicle Stuck in Park / "Shift to Park" Message?
Second-generation Terrains with the electronic precision (push-button/monostable) shifter throw a persistent "Shift to Park" warning and refuse to shift out of (or fully into) park even when correctly positioned. GM traced it to build-up/contamination on the Park switch contacts… Repairs typically run $150-$1,500. Severity: medium.
What is the 2018-2024 GMC Terrain Charge Air Cooler Moisture Freeze-Up - Misfire, Underboost and Reduced Engine Power in Cold Weather?
On the second-generation Terrain (2018+) with the turbocharged 1.5L LYX or 2.0L LTG engine, the air-to-air charge air cooler (intercooler) accumulates condensate from humid or rainy driving plus PCV-borne moisture. In cold ambient temperatures that water freezes inside the CAC co… Repairs typically run $150-$900. Severity: medium.
What is the 2010-2024 GMC Terrain Wheel Bearing / Hub Assembly Magnetic Encoder Ring Failure - ABS and Traction Lights Without Bearing Noise?
Terrain front and rear hub assemblies integrate the ABS magnetic encoder ring into the bearing's inboard seal, where it sits directly exposed to road salt and moisture. Two distinct failure modes result. The mechanical one is the familiar humming or roaring that rises with speed… Repairs typically run $300-$800. Severity: medium.
What is the 2013-2019 GMC Terrain IntelliLink Infotainment Freezing/Rebooting and Backup Camera Black Screen?
The IntelliLink/MyLink touchscreen freezes and spontaneously reboots, losing control of radio, climate, navigation and Bluetooth, and often displays a black screen or a frozen backup-camera image. During a reboot, phone calls drop and the rear camera can go dark while in reverse… Repairs typically run $100-$900. Severity: low.
Content on this page was compiled with AI assistance using NHTSA complaints, TSBs, owner reports, and public automotive data. While we strive for accuracy, this information may contain errors. Always verify repair procedures and specifications with your vehicle's service manual or a qualified mechanic.
