Understanding P0175 on the 2022 Mercedes-Benz GLE
The P0175 diagnostic trouble code on your 2022 Mercedes-Benz GLE signals that Bank 2 of the engine is running an excessively rich air-fuel mixture. The 2022 GLE is available with the M264 turbocharged 2.0L four-cylinder producing 255 hp, or the M256 mild-hybrid 3.0L inline-six turbo making 362 hp. Both engines use sophisticated direct injection and turbocharging, and a rich condition on Bank 2 means the ECM's fuel trim corrections have exceeded their normal range.
When the long-term fuel trim on Bank 2 drops below approximately -25%, the ECM determines it can no longer compensate for the excess fuel and sets the P0175 code. This triggers the check engine light and stores freeze frame data for diagnostic purposes.
Symptoms You May Experience
- Illuminated check engine light (steady, not flashing)
- Reduced fuel economy — expect 2-5 MPG less than normal
- Sulfur or rotten egg smell from the exhaust
- Black soot deposits on tailpipe
- Rough or uneven idle, especially when cold
- Hesitation or stumbling during acceleration
Most Likely Causes for the 2022 GLE
1. Dirty or Failed MAF Sensor — High Likelihood
The 2022 GLE's hot-film MAF sensor is positioned in the intake tract before the turbocharger. Mercedes engines using the M264 and M256 platforms have a known sensitivity to MAF contamination from oil vapors that pass through the crankcase ventilation system. When the sensor's hot-film element becomes coated, it underreads airflow, causing the ECM to under-correct and run rich. A quick diagnostic involves comparing MAF readings at idle and under load against Mercedes specifications using STAR Diagnostic or a quality aftermarket scanner.
2. Leaking Fuel Injectors — Medium Likelihood
The high-pressure piezo injectors on Mercedes direct injection engines operate at extreme pressures. By the 2022 model year, these injectors are refined but not immune to issues. A leaking injector on Bank 2 will drip fuel into the cylinder even when it should be closed, enriching the mixture. Symptoms are often worse at cold startup when fuel doesn't vaporize as readily. An injector balance test and leak-down test can pinpoint the offending injector.
3. Upstream O2 Sensor Degradation — Medium Likelihood
The wideband O2 sensor (also called an air-fuel ratio sensor) on Bank 2 is essential for closed-loop fuel control. On the 2022 GLE, this sensor is exposed to high exhaust temperatures, especially on the turbo engines. A lazy or biased sensor can report lean when the mixture is actually correct, causing the ECM to add unnecessary fuel. Monitoring sensor response time and voltage patterns reveals degradation before complete failure.
4. Stuck-Open Fuel Pressure Regulator — Low Likelihood
The electronically controlled fuel pressure regulator on the high-pressure fuel pump manages rail pressure for the direct injection system. If it allows excessive pressure, more fuel than intended enters the cylinders. This is uncommon on the 2022 model but worth checking if other causes are ruled out. A fuel pressure gauge test at idle and under load will confirm or eliminate this possibility.
Step-by-Step Diagnosis
- Scan for all stored and pending codes — check for companion codes like P0172 (Bank 1 rich) or misfire codes
- Review freeze frame data to understand engine load, RPM, and temperature when the code triggered
- Check short-term and long-term fuel trims on Bank 2 at idle and 2,500 RPM
- Inspect and test the MAF sensor — clean with CRC MAF cleaner if contaminated
- Perform fuel injector leak-down and balance tests
- Monitor Bank 2 upstream O2 sensor waveform for response speed
- Measure fuel rail pressure at idle and under load
Repair Cost Estimates
- MAF sensor: $250–$450 including labor at an independent shop
- Fuel injector (each): $350–$650 per injector
- O2 sensor: $280–$500
- Fuel pressure regulator/pump assembly: $500–$900
DIY Feasibility
MAF sensor replacement is the most accessible DIY repair on the 2022 GLE — it typically involves removing the air intake duct and unbolting two screws. O2 sensor replacement requires getting under the vehicle and dealing with heat-seized threads. Injector and fuel pressure work on Mercedes high-pressure systems should be performed by trained technicians with proper safety equipment, as fuel pressures can be dangerously high.