System too rich (Bank 1)
What P0172 means
Your car's computer set P0172: System too rich (Bank 1). It belongs to the fuel and air metering group of codes. It is a generic code, so it means the same thing on every make. The check engine light usually comes on once the fault has been seen on two drives in a row. Until then it shows up as a pending code.
Can I keep driving? Usually safe to drive for now, but get it checked soon. Left alone it can lower fuel economy, fail an emissions test or lead to a bigger repair.
Common causes
- Leaking fuel injector
- Stuck-open EVAP purge valve
- Dirty MAF sensor reading too high
- High fuel pressure or a bad pressure regulator
Fix the cheapest, most likely cause first. Clearing the code without a repair only turns the light off until the fault comes back.
Check it yourself
Watch fuel trims: large negative trims mean the computer is pulling fuel out.
Torque Deck reads P0172 with a cheap Bluetooth OBD2 adapter. It also shows the freeze frame (engine conditions at the moment the code set) and the live data you need to narrow it down.
Related codes
This page explains what the code usually means. It is not a diagnosis of your car. When in doubt, ask a mechanic.