What Does P0172 Mean on Your 2024 Mercedes-Benz E-Class?
A P0172 code on your 2024 Mercedes-Benz E-Class (W214) means the engine management system has detected a rich air-fuel condition on Bank 1. The 2024 E 350 uses the M254 2.0-liter turbocharged four-cylinder engine with a 48-volt mild-hybrid system producing 255 horsepower, while the E 450 adds an electric motor for a combined 375 horsepower. The four-cylinder is a single-bank engine, so P0172 affects the entire combustion system.
The E-Class is a flagship luxury sedan, and maintaining proper engine calibration is essential for both performance and longevity. A rich condition should be diagnosed and corrected promptly.
Symptoms You Might Notice
- Check engine light on the MBUX display
- Lower fuel efficiency than expected
- Dark or black exhaust smoke
- Fuel smell from the tailpipe
- Rough or inconsistent idle
- Reduced power or turbo lag
Common Causes of P0172 on the 2024 E-Class
- Contaminated MAF Sensor - The M254 engine's hot-film air mass sensor is critical for fuel metering. Contamination from oil vapor or debris causes inaccurate readings and over-fueling.
- Direct Fuel Injector Leak - High-pressure piezo injectors can develop early failures from manufacturing defects or fuel quality issues, introducing excess fuel.
- Crankcase Ventilation System Issue - The CCV system can allow excessive oil vapors into the intake, creating a rich mixture that exceeds the ECU's correction range.
- Faulty Lambda Sensor - The upstream wideband oxygen sensor provides the primary feedback signal. If it drifts or fails, fuel metering becomes inaccurate.
How to Diagnose the Problem
Use Mercedes Xentry diagnostic software or a compatible tool. Read fault codes and review fuel trim adaptation values. Negative multiplicative corrections on Bank 1 confirm the ECU is actively reducing fuel to counteract rich running.
Inspect the air filter and clean the MAF sensor. Check the intake manifold for oil residue. Monitor the lambda sensor output with live data. If the code persists after basic maintenance, perform injector testing. The 2024 E-Class is under warranty, so dealer diagnosis is the recommended first step.
Repair Options and Cost Breakdown
- Air filter replacement - $35 to $70.
- MAF sensor cleaning or replacement - $15 to $480.
- Lambda sensor replacement - $300 to $550.
- Direct fuel injector replacement - $480 to $1,000.
- Crankcase ventilation valve replacement - $270 to $520.
Prevention Tips
Use premium fuel (91 octane minimum) as required. Follow the Mercedes maintenance schedule with approved synthetic oil. The M254 engine benefits from Top Tier gasoline to keep the direct injection system clean. Replace the air filter on schedule. Monitoring fuel economy is the easiest way to catch a developing rich condition early.