OBD-II code guide
P0172 System Too Rich Bank 1
P0172 means the engine computer is removing fuel because bank 1 appears to be running too rich.
What it means
The air-fuel mixture has too much fuel or not enough air on bank 1.
Common symptoms
- Black exhaust smoke
- Fuel smell
- Poor fuel economy
- Rough idle
- Check engine light
Likely causes
- Dirty air filter
- Leaking injector
- MAF sensor error
- High fuel pressure
- Faulty oxygen sensor data
First checks
- Inspect air intake restrictions.
- Check MAF readings and fuel trims.
- Look for leaking injectors.
- Do not replace oxygen sensors without confirming data.