P0175 on the 2022 GMC Terrain: Turbo Four-Cylinder
The 2022 GMC Terrain is powered by the 1.5L turbocharged four-cylinder engine (LYX) producing 170 hp and 203 lb-ft of torque. This engine uses a combination of direct and port fuel injection (dual injection), turbocharging, and continuously variable valve timing. While it's an inline-four, GM's engine management can still generate Bank 2 codes based on how it partitions fuel trim monitoring.
P0175 means the ECM has detected that the engine is running too rich on one monitoring zone, with fuel trims exceeding correction limits.
Symptoms
- Check engine light on
- Fuel economy below the expected 26-30 MPG range
- Rough or vibrating idle
- Gasoline smell from the exhaust
- Black residue on the tailpipe
- Sluggish throttle response
- Turbo boost may feel inconsistent
Causes on the 1.5T Terrain
1. MAF Sensor Contamination — High Likelihood
The Terrain's 1.5L turbo uses a hot-wire MAF sensor in the intake tract ahead of the turbocharger. Like most turbocharged engines, PCV vapors route through the intake and contaminate the MAF element over time. After 25,000-55,000 miles, enough contamination accumulates to affect accuracy. The turbocharger amplifies MAF errors because boost calculations depend on accurate intake air measurement.
2. O2 Sensor Degradation — Medium Likelihood
The upstream wideband O2 sensor provides critical feedback for fuel trim control. The 1.5T generates high exhaust temperatures under boost, which accelerates sensor aging. A slow or biased sensor causes the ECM to add unnecessary fuel. Testing with a GM-compatible scan tool reveals response time and voltage accuracy.
3. EVAP Purge Valve — Medium Likelihood
GM's EVAP purge valve is a known reliability concern. A stuck-open valve introduces continuous fuel vapors into the intake. On the smaller 1.5L engine, purge valve vapor has a proportionally larger impact than on V8 engines. This is a cheap, easy fix worth checking early.
4. Boost System Leak — Low Likelihood
The turbo charge pipes and intercooler connections on the 1.5T can develop leaks from heat cycling. Air escaping after the MAF sensor has measured it creates a rich condition because the ECM delivered fuel for air that never reached the cylinders. A smoke test or boost pressure test identifies leaks.
Diagnostic Steps
- Scan for all codes with a GM-compatible scanner
- Monitor fuel trims at idle and under load
- Test MAF sensor readings against GM 1.5T specifications
- Monitor O2 sensor response
- Check EVAP purge valve — disconnect hose at idle to test
- Perform boost pressure test if other causes are ruled out
Repair Costs
- MAF sensor: $100–$240
- O2 sensor: $120–$280
- EVAP purge valve: $50–$140
- Boost pipe repair: $80–$200
DIY Feasibility
The Terrain's engine bay is compact but reasonably accessible. MAF sensor and EVAP purge valve replacements are straightforward DIY jobs. O2 sensor access requires working underneath. Boost system inspection can be done visually. If still under GM's 3-year/36,000-mile warranty, let the dealer handle it.