What P0174 Means on Your 2021 GMC Yukon
A P0174 code on your 2021 GMC Yukon indicates Bank 2 is running with a lean air-fuel mixture. The 2021 Yukon offers the 5.3L V8 (355 hp), 6.2L V8 (420 hp), and 3.0L Duramax turbo-diesel inline-six. On the V8 engines, Bank 2 is the driver side (left side). The ECM has detected that fuel trim corrections on Bank 2 exceed the allowable range.
The Yukon is a full-size SUV often loaded with passengers and cargo. Maintaining proper engine performance is important for safety and reliability.
Symptoms
- Check engine light on
- Rough idle
- Reduced power during acceleration
- Higher fuel consumption
- Engine hesitation
- Possible knocking under load
Common Causes
- Vacuum Leak (30% likelihood) – Intake manifold gaskets, PCV hoses, and brake booster lines. GM V8 intake systems have multiple sealing surfaces that can develop leaks.
- Fuel Injector Issue (25% likelihood) – Clogged or failing injectors on Bank 2. The Dynamic Fuel Management system in the 5.3L and 6.2L can contribute to injector carbon buildup.
- MAF Sensor Contamination (25% likelihood) – Dirt or oil vapor on the MAF sensor element causes inaccurate airflow readings.
- Exhaust Leak (20% likelihood) – Manifold gasket or bolt failure on the driver side allowing air ingestion near the O2 sensor.
Diagnosis
- Compare bank fuel trims – Isolate the problem to Bank 2 or identify system-wide issues.
- Smoke test the intake – Find vacuum leaks throughout the intake system.
- Test fuel injectors – Balance test on Bank 2 cylinders.
- Clean and test MAF – Compare live data to GM specifications.
- Inspect exhaust manifolds – Check for leaks on the driver side.
Repair Costs
- Vacuum leak – $80–$500. Intake gasket: $300–$700.
- Fuel injector – Single: $100–$280. Labor: $200–$400.
- MAF sensor – Cleaning: $10. Replacement: $80–$250.
- Exhaust manifold – $200–$800.
DIY Options
The Yukon's V8 engine bay is spacious and accessible. MAF cleaning takes 15 minutes. Visual inspections for vacuum leaks are straightforward. Intake manifold gasket work is an intermediate DIY project. Exhaust manifold work depends on bolt condition, which can be challenging on older vehicles.
Prevention
- Use Top Tier gasoline to keep injectors clean
- Replace the air filter every 20,000 miles
- Inspect intake and exhaust components regularly
- Follow GM's recommended maintenance schedule
- Address any drivability changes promptly