P0174 on the 2022 Buick Encore GX
The 2022 Buick Encore GX is available with two small-displacement turbocharged three-cylinder engines: a 1.2L turbo (L8B, 137 hp) and a 1.3L turbo (L3T, 155 hp). Since these are three-cylinder inline engines, P0174 (System Too Lean Bank 2) indicates a generalized lean condition — the PCM has detected that the air-fuel mixture has too much air or insufficient fuel. The long-term fuel trims have exceeded the normal correction range.
Symptoms to Watch For
- Check engine light on
- Rough or vibrating idle (three-cylinders naturally vibrate more)
- Hesitation or lag during acceleration
- Reduced turbo boost response
- Fuel economy below the expected 30+ MPG
Common Causes on the Encore GX Turbo Engines
1. Boost Leaks
Both Encore GX engines are turbocharged with charge piping, an intercooler, and various coupler connections. On these smaller turbo engines, the charge piping is compact but still has multiple connection points that can leak. A loose clamp, cracked coupler, or failing diverter valve allows pressurized air to escape after the MAF sensor, creating a lean condition. A boost leak test at 10-15 psi is the fastest diagnostic approach.
2. MAF Sensor Contamination
The small turbo engines in the Encore GX are sensitive to MAF sensor accuracy because even small errors in airflow measurement result in proportionally larger fuel delivery mistakes on a low-displacement engine. PCV oil vapor and dust can foul the MAF element. Clean with MAF-specific spray as a first diagnostic step.
3. Fuel Delivery Problems
The direct injection systems on both engines use cam-driven high-pressure pumps. A weak pump or restricted injector on an engine with only three cylinders means each cylinder's contribution to overall performance is more significant. Fuel pressure testing via a scan tool is necessary to evaluate the high-pressure system.
4. Intake Gasket or PCV Leak
The intake manifold gasket or PCV system can develop leaks allowing unmetered air into the intake. On these small engines, even a minor leak has a proportionally larger effect on the air-fuel ratio. Smoke testing the intake system reveals these leaks.
Diagnostic Steps
- Scan for all DTCs and review freeze frame data
- Check long-term fuel trim values — above +10% confirms the lean condition
- Perform a boost leak test on the charge air system
- Inspect all charge pipe connections and the diverter valve
- Clean and test the MAF sensor
- Monitor fuel pressure at idle and under boost
Repair Cost Estimates
The Encore GX uses affordable GM components:
- Boost leak repair (hose/clamp): $100–$300
- MAF sensor cleaning: $15–$30 (DIY)
- MAF sensor replacement: $120–$250
- Fuel pump replacement: $350–$650
- PCV valve or gasket repair: $80–$200
Can You Drive With P0174?
The small turbo engines are more sensitive to lean conditions than larger powerplants. Running lean under boost on a 1.2L or 1.3L three-cylinder can cause knock and overheating more quickly due to the smaller combustion chambers. Avoid hard acceleration and highway merging under full throttle. Have it diagnosed within 1-2 weeks.
DIY Feasibility
The Encore GX engine bay is compact but accessible for basic maintenance. MAF sensor cleaning is straightforward. Inspecting boost piping and clamps is a visual task. Boost leak testing requires a simple adapter but is a common DIY procedure. For fuel system diagnostics, a shop with GM scan tool capability is recommended.