P0174 on the 2022 Buick Envision
The 2022 Buick Envision is powered by a 2.0L turbocharged four-cylinder engine (LSY) producing 228 horsepower and 258 lb-ft of torque, paired with a 9-speed automatic transmission. P0174 indicates the PCM has detected a lean condition — the air-fuel mixture has excess air or insufficient fuel. Since the LSY is an inline-four, P0174 represents a generalized lean state where long-term fuel trims have exceeded normal limits.
Symptoms
- Check engine light on
- Rough or inconsistent idle
- Hesitation during acceleration
- Reduced turbo boost response
- Decreased fuel economy below the typical 26-31 MPG
Common Causes on the LSY 2.0L Turbo
1. Boost Leaks
The LSY turbo engine uses a single turbocharger with an air-to-air intercooler and charge piping. Common boost leak locations include the intercooler-to-pipe connections, charge pipe coupler at the throttle body, and the diverter valve. The Envision's charge piping routes through the front of the engine bay with several connection points. A boost leak test using 15-20 psi of regulated air through the intake system is the most effective diagnostic method.
2. MAF Sensor Contamination
The hot-wire MAF sensor is positioned in the air intake duct upstream of the turbocharger. PCV oil vapor, dust, or aftermarket air filter oil can coat the sensing element. The LSY engine's PCV system routes crankcase gases back into the intake, providing a constant source of potential contamination. A fouled MAF underreports airflow, causing lean fuel delivery.
3. Fuel System Issues
The LSY uses direct fuel injection with a high-pressure fuel pump. GM's direct injection system is generally robust, but a failing pump, restricted fuel filter, or partially clogged injector can limit fuel delivery. Under boost, fuel demand increases significantly, making marginal pump performance more apparent.
4. PCV Valve Malfunction
The PCV system on the LSY manages crankcase pressure and blow-by gases. A stuck-open PCV valve or cracked PCV hose introduces unmetered air into the intake manifold. Inspect the PCV valve and all connecting hoses for proper operation and condition.
Diagnostic Procedure
- Scan for all DTCs and review freeze frame data
- Check long-term fuel trim values — above +10% confirms lean condition
- Perform a boost leak test on the charge air system
- Inspect all charge pipe connections, intercooler hoses, and clamps
- Clean and evaluate the MAF sensor
- Monitor fuel pressure at idle and under boost via scan tool
Repair Cost Estimates
Buick parts are moderately priced:
- Boost leak repair (hose/clamp): $100–$350
- MAF sensor cleaning: $15–$35 (DIY)
- MAF sensor replacement: $130–$280
- High-pressure fuel pump: $400–$700
- PCV valve replacement: $60–$150
Driving With P0174
Running lean on the turbocharged LSY engine is a concern under boost. Lean mixtures at elevated boost pressures can cause detonation. Avoid hard acceleration, towing, and driving in sport mode. Light daily driving is acceptable for the short term. The 2022 Envision may still be under Buick's 4-year/50,000-mile warranty.
DIY Feasibility
The Envision's engine bay offers decent access. MAF sensor cleaning is a quick DIY task. Inspecting boost piping and clamps is straightforward. A boost leak test can be performed with a homemade adapter and air compressor. For fuel pressure diagnostics, a GM-compatible scan tool is needed. Under warranty, let the dealer handle the repair.