OBD CodesWhat it means
The computer makes a fine correction to fuelling using the oxygen sensor after the catalytic converter. These codes mean that correction has reached its limit. The mixture looks slightly wrong when measured after the converter.
Codes in this group
| Code | Meaning |
|---|---|
| P2096 | Post-catalyst fuel trim too lean, bank 1 |
| P2097 | Post-catalyst fuel trim too rich, bank 1 |
| P2098 | Post-catalyst fuel trim too lean, bank 2 |
| P2099 | Post-catalyst fuel trim too rich, 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
- Usually none
- Sometimes slightly higher fuel use
Common causes
Most likely first:
- An exhaust leak between the two oxygen sensors
- An ageing oxygen sensor, front or rear
- A small vacuum leak or fuel pressure problem
- A catalytic converter nearing the end of its life
What to check first
- Check for exhaust leaks and blowing joints
- See whether other mixture or sensor codes are stored: they usually point to the real cause
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.