P0175 on the 2021 GMC Yukon: Full-Size SUV V8 Diagnosis
The 2021 GMC Yukon was the first year of the fifth-generation (GMT T1XX) platform, featuring GM's Gen V small-block V8 engines — the 5.3L L84 (355 hp) and the 6.2L L87 (420 hp). Both engines use Dynamic Fuel Management (DFM), direct fuel injection, and variable valve timing. With a true V8 Bank 2 on the passenger side (cylinders 2, 4, 6, 8), P0175 means that bank is running too rich for the ECM to correct.
At 3-5 years old with potentially 30,000-70,000 miles, the 2021 Yukon is at the age where sensor contamination and early component wear can trigger this code.
Symptoms in Your Yukon
- Check engine light on the large digital dashboard display
- Fuel economy below the expected 15-22 MPG range
- Rough or shaking idle at stop lights
- Rich exhaust smell — noticeable in the garage
- Black soot on the dual exhaust tips
- DFM cylinder deactivation may feel rough
- Reduced towing performance
Why Your 2021 Yukon V8 Is Running Rich
1. MAF Sensor Contamination — High Likelihood
The Yukon's V8 engines draw large volumes of air through a MAF sensor that's exposed to PCV oil vapors from the direct injection crankcase. After 30,000-70,000 miles, enough contamination accumulates to degrade MAF accuracy. The Yukon's typical suburban and highway duty cycle may seem gentle, but the constant air volume through the MAF provides ample opportunity for contamination. Even a 5% underreading on the 5.3L or 6.2L translates to a significant fuel delivery error.
2. O2 Sensor Aging — Medium Likelihood
The upstream wideband O2 sensor on Bank 2 has been through thousands of heat cycles over years of driving. GM V8 exhaust manifolds produce substantial heat, and the sensor must withstand extreme temperature swings. A sensor losing responsiveness causes the ECM to work with delayed data, resulting in fuel delivery overcorrection.
3. GDI Fuel Injector Carbon Buildup — Medium Likelihood
Direct injection engines are prone to carbon deposits on injector tips. After 30,000+ miles, these deposits can alter the spray pattern of Bank 2 injectors, causing uneven fuel distribution and over-delivery. The Yukon's engines use eight high-pressure injectors, and even one underperforming injector on Bank 2 can push fuel trims past the correction limit.
4. EVAP Purge Valve — Low Likelihood
GM's EVAP purge valve is a known failure point. A stuck-open valve introduces continuous fuel vapors into the intake. On the Yukon, the purge valve is accessible near the intake manifold and is an affordable replacement part. Testing by disconnecting the purge line at idle reveals whether this is the cause.
Diagnostic Procedure
- Scan for codes with a GM-compatible scanner
- Compare Bank 1 and Bank 2 fuel trims at idle and 2,000 RPM
- Test MAF sensor readings against GM V8 specifications
- Monitor O2 sensor response times — compare banks
- Check EVAP purge valve operation
- Verify fuel pressure at the high-pressure rail
Repair Costs
- MAF sensor: $90–$250
- O2 sensor: $110–$290
- Fuel injector (each): $140–$340
- EVAP purge valve: $50–$140
DIY or Professional?
The Yukon's engine bay is spacious with good access to most components. MAF sensor and EVAP purge valve are easy DIY repairs. O2 sensor access requires getting under the vehicle. GDI injector work should be performed by professionals familiar with the high-pressure fuel system. If still under GM's warranty, the dealer handles it at no charge.