OBD CodesWhat it means
"Rich" means too much fuel for the air. The computer has cut fuel as far as it is allowed and the mixture is still rich. Running rich for long wastes fuel and can overheat and damage the catalytic converter.
Codes in this group
| Code | Meaning |
|---|---|
| P0172 | Mixture too rich, bank 1 |
| P0175 | Mixture too rich, bank 2 |
| P2188 | Mixture too rich at idle, bank 1 |
| P2190 | Mixture too rich at idle, bank 2 |
Bank 1 is the side of the engine that has cylinder 1. Sensor 1 is before the catalytic converter and sensor 2 is after it. More terms explained.
What you may notice
- Smell of fuel from the exhaust
- Black smoke or sooty tailpipe
- High fuel use
- Rough idle
Common causes
Most likely first:
- A leaking injector
- Fuel pressure too high from a faulty regulator
- A coolant temperature sensor that tells the computer the engine is cold
- A clogged air filter
- A faulty mass air flow sensor
What to check first
- Check the air filter
- Pull the oil dipstick: a strong fuel smell in the oil means fuel is getting past, so have it seen quickly
- Avoid long drives until fixed to protect the catalytic converter
Have a mechanic confirm. A fault code tells you which system reported a problem, not which part has failed. The same code can have several causes, and they differ between car models. Use this page to understand the code, then have a qualified mechanic test the car before any part is replaced.
After the repair
Once the cause is fixed, the code can be cleared with a scan tool, or the warning light goes out by itself after several trips without the fault. Clearing a code without fixing the cause only hides it for a while. More about clearing codes.
Related codes
Mass air flow (MAF) sensor (P0100), Manifold pressure (MAP) and barometric sensor (P0105), Intake air temperature sensor (P0110), Engine coolant temperature sensor (P0115), Thermostat and engine warm-up (P0125), Throttle position sensor (P0120), Accelerator pedal sensor and throttle agreement (P2120), Electronic throttle actuator (P2100). All codes.
Written in November 2026. These are generic OBD-II codes, the same on all makes. Causes and repair steps differ between models.