What Does P0172 Mean on Your 2022 Mercedes-Benz E-Class?
When your 2022 Mercedes-Benz E-Class (W213) triggers a P0172 code, the engine management system has determined that Bank 1 is running too rich. The 2022 E 350 uses the M264 2.0-liter turbocharged four-cylinder with 255 horsepower, while the E 450 features the M256 3.0-liter turbocharged inline-six with a 48-volt EQ Boost system producing 362 horsepower. Both engines use direct fuel injection and are engineered for precise fuel control.
A rich condition on either of these engines deserves prompt attention. Excess fuel damages emission components and can affect the turbocharger and mild-hybrid system performance.
Symptoms You Might Notice
- Check engine light on
- Increased fuel consumption
- Black exhaust smoke under acceleration
- Fuel smell from the exhaust
- Rough or unstable idle
- Reduced power or boost delivery
Common Causes of P0172 on the 2022 E-Class
- Contaminated MAF Sensor - Oil vapor and debris contaminate the hot-film mass airflow sensor, causing under-reading of airflow and triggering over-fueling by the ECU.
- Crankcase Ventilation Valve Failure - The CCV valve can deteriorate with age and allow excessive crankcase vapors into the intake. This is a common cause on Mercedes turbo engines.
- Leaking Direct Fuel Injector - High-pressure injectors on both the M264 and M256 can develop carbon deposits or seal failures, especially as mileage accumulates.
- Upstream Lambda Sensor Issue - A drifting or slow-responding lambda sensor provides inaccurate feedback, causing the ECU to over-enrich the mixture.
How to Diagnose the Problem
Use a Mercedes Star Diagnostic tool or compatible scanner. Read fault codes and fuel adaptation values. Negative multiplicative fuel corrections confirm a rich condition. On the inline-six, check both bank-specific and overall adaptations.
Start with an air filter inspection and MAF sensor cleaning. Look for oil in the intake manifold. Test the lambda sensor response time. If corrections remain negative, perform injector diagnostics. Check for any applicable Mercedes technical service bulletins for your specific engine.
Repair Options and Cost Breakdown
- Air filter replacement - $35 to $65.
- MAF sensor cleaning or replacement - $15 to $460.
- Crankcase ventilation valve replacement - $260 to $510.
- Lambda sensor replacement - $280 to $520.
- Direct fuel injector replacement - $450 to $980.
Prevention Tips
Premium fuel is required for both engines. Use Mercedes-approved synthetic oil and follow the service schedule. The M256 inline-six benefits from periodic fuel system cleaning to prevent carbon buildup on the direct injection system. Monitor your fuel economy and have any decline investigated. Early intervention prevents costly catalytic converter and turbocharger repairs.