What does code P0172 mean on a Mercedes-Benz and is it safe to drive?
P0172: System Too Rich (Bank 1). Here's what it means on your Mercedes-Benz, what usually causes it, what repairs typically cost, and how safe it is to keep driving.
PowertrainMedium urgency
What this code means
Too much fuel relative to air. O2 sensor detects low oxygen in exhaust; PCM is reducing fuel trim.
Common causes for your Mercedes-Benz
- Faulty MAF or O2 sensor
- Leaking fuel injector(s)
- High fuel pressure
- Faulty purge valve stuck open
Symptoms
- Check Engine Light
- Rich smell, black smoke
- Poor fuel economy
- Rough idle possible
Typical fixes
- Replace MAF or O2 sensor
- Test fuel pressure and injectors
- Replace purge valve if stuck open
Repair cost range
For a Mercedes-Benz, repairs for P0172 often fall between $100 and $600, depending on the cause and whether you use OEM or aftermarket parts. Labor rates vary by location.
Known issues on Mercedes-Benz
Mercedes M271 turbo P0172 rich Bank 1 often comes from a stuck-open EVAP purge valve or a leaking fuel injector. On the M271 turbocharged engine, a boost leak causing ECU over-fueling can also trigger P0172—check the charge pipe connections and intercooler hoses.
Most commonly affected models
C250 M271 Turbo 2012–2015E250 M271 2011–2013