What does code P0172 mean on a Mitsubishi and is it safe to drive?
P0172: System Too Rich (Bank 1). Here's what it means on your Mitsubishi, 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 Mitsubishi
- 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 Mitsubishi, 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 Mitsubishi
Mitsubishi 4G69 P0172 rich Bank 1 is typically a stuck-open EVAP purge valve or a leaking fuel injector. On older 4G63 turbo models, a failing boost sensor or fuel pressure regulator can cause over-fueling. Check the purge valve first, then fuel pressure regulator.
Most commonly affected models
Outlander 2.4L 4G69 2004–2012Lancer 2.0L 4G63 2002–2007