What are the most common GMC Terrain problems?

According to Au7o's analysis of 740+ owner reports, the 2020-2020 GMC Terrain has 1 documented issues. The most frequently reported are: 1.5L Turbo PCV System Failure and Coolant/Oil Intrusion. Of these, 1 is rated critical and should be addressed promptly.

Is the GMC Terrain reliable?

The 2020-2020 GMC Terrain has 1 known issues documented across 740+ owner reports. 1 issue is rated critical: 1.5L Turbo PCV System Failure and Coolant/Oil Intrusion. 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 $400 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.

2020 GMC Terrain Problems: 1 Issues Every Owner Should Know

2020 GMC Terrain Problems: 1 Issues Every Owner Should Know | Au7o

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Community Reported

740 owners

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.

This issue also affects: Audi A3, Audi A6, Audi Q5

Common Symptoms

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).

What Owners Are Using

Parts and tips from 740+ owners who fixed this issue

UpgradeGM 12690058 updated valve cover with revised PCV diaphragm for 2018-2023 Terrain 1.5T (LFV/LYX) — this is the complete valve cover assembly including the integrated PCV valve. The original diaphragm tears at the edges under sustained boost pressure. The updated design uses a reinforced diaphragm and revised attachment method. This part also fits the Equinox 1.5T (same engine family). (GM OEM #12690058)
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UpgradeAfter replacing the valve cover, remove the intercooler outlet pipe and inspect for oily residue. If significant oil contamination is present in the intercooler, clean the entire intake side with brake cleaner before reinstalling — oil in the intercooler degrades boost efficiency and can cause pre-detonation. If coolant is also present in the intercooler (milky fluid), the air-to-water intercooler heat exchanger (GM 84446987) must be replaced separately. (GM #84446987)
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NoteThe 1.5T coolant-into-cylinder issue on Terrain has resulted in total engine failures where coolant hydrolock damages pistons and connecting rods. If you see both dropping coolant AND blue/white smoke simultaneously, do not drive the vehicle. Have it inspected immediately for coolant in cylinders (compression test + coolant in oil check). Continued driving after coolant intrusion typically destroys at least one cylinder and requires engine replacement ($5,000-8,000).

Typical repair cost:$400 - $2,800

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740+ owners have reported this issue

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Community Reported

High Confidence740 reportsLast reported by owners Feb 2026Reviewed Feb 2026

2020 GMC Terrain Problems: 1 Issues Every Owner Should Know

All 1 Known Issues

2018-2025 GMC Terrain: 1.5L Turbo PCV System Failure and Coolant/Oil Intrusion#