P0175 on the 2020 Mercedes-Benz GLE: What's Going On?
The 2020 model year marked the second generation (W167) of the Mercedes-Benz GLE, and it brought significant powertrain changes. The base GLE 350 uses the M264 2.0L turbocharged four-cylinder, while the GLE 450 features the M256 3.0L inline-six with EQ Boost mild-hybrid technology. When either of these engines throws a P0175 code, it means Bank 2 is consistently running richer than the ECM can compensate for through normal fuel trim adjustments.
At this age, the 2020 GLE is approaching or past its initial warranty coverage for many owners. With 40,000-80,000 miles on the odometer, certain fuel system components are reaching the point where wear-related issues can trigger this code.
Telltale Signs of a Rich Condition
- Check engine light on (MIL illuminated)
- Fuel economy dropping noticeably — filling up more often than usual
- Exhaust smells strongly of unburned fuel
- Dark or sooty residue accumulating at the tailpipe
- Engine runs rough at idle, especially when first started
- Occasional misfires or hesitation during acceleration
Why Your 2020 GLE Is Running Rich on Bank 2
1. MAF Sensor Contamination — High Likelihood
With 4-6 years of service, the hot-film MAF sensor in the 2020 GLE's intake system has had ample time to accumulate oil vapor residue and particulate contamination. The M264 and M256 engines both use positive crankcase ventilation systems that route oil-laden vapors through the intake, gradually coating the MAF element. This causes the sensor to underread actual airflow, and the ECM responds by not removing enough fuel — resulting in a rich condition. At this mileage, MAF cleaning may provide temporary relief, but replacement often provides the lasting fix.
2. Worn or Leaking Fuel Injectors — Medium Likelihood
Direct injection technology puts enormous stress on fuel injectors. The 2020 GLE's piezo injectors fire at pressures up to 2,900 PSI and cycle millions of times over their service life. By this point, injector tip deposits and seal degradation can cause injectors on Bank 2 to deliver more fuel than commanded. Carbon buildup on the injector tips — a common issue with direct injection — can also alter spray patterns and worsen combustion efficiency.
3. Bank 2 O2 Sensor Failure — Medium Likelihood
Oxygen sensors on the 2020 GLE have now been exposed to years of high exhaust temperatures. The wideband air-fuel ratio sensor upstream of the catalytic converter on Bank 2 is particularly vulnerable. If this sensor begins reporting inaccurately, the ECM's closed-loop fuel control goes awry. Common signs of O2 sensor failure include slow response times (over 100ms) and a narrowed voltage swing range.
4. Vacuum Leaks or EVAP System Issues — Low Likelihood
While vacuum leaks typically cause lean conditions, a malfunctioning EVAP purge valve that's stuck open can flood the intake with fuel vapors, enriching the mixture on Bank 2. The 2020 GLE's EVAP system includes a purge valve and canister that can develop issues as they age. A smoke test can quickly reveal any vacuum leaks or EVAP system faults.
Diagnostic Approach
- Pull all codes and review freeze frame data with a Mercedes-compatible scanner
- Monitor live fuel trim data — long-term fuel trim below -20% on Bank 2 confirms the rich condition
- Test MAF sensor output at idle (should read approximately 8-12 g/s) and at 2,500 RPM
- Perform injector flow and leak-down tests
- Evaluate O2 sensor waveforms for response time and voltage accuracy
- Conduct a smoke test to check for EVAP leaks
- Verify fuel pressure meets Mercedes specification at idle and under load
What Will Repairs Cost?
- MAF sensor replacement: $230–$420
- Fuel injector replacement (per injector): $300–$650
- O2 sensor replacement: $270–$480
- EVAP purge valve: $150–$300
These estimates reflect independent Mercedes shop pricing. Dealership rates may be 30-50% higher.
DIY Considerations
The 2020 GLE is not the most DIY-friendly vehicle. The MAF sensor is accessible and can be replaced with basic tools. However, fuel injector replacement on the direct injection system requires specialized tools and knowledge of the high-pressure fuel system safety procedures. O2 sensor access depends on which bank — Bank 2 sensors on the GLE often require removing heat shields and working in tight spaces underneath the vehicle.