P2097Post Catalyst Fuel Trim System Too Rich (Bank 1)
What it means
The downstream oxygen sensor on bank 1 keeps reading rich, so the ECU's fine correction based on it has reached its limit.
Symptoms
- Check engine light
- Possibly higher fuel consumption
Common causes
- Rich fuelling (leaking injector, high fuel pressure)
- Faulty oxygen sensor
- Oil or coolant contamination of the catalyst
What to check first
- Check for exhaust leaks around both oxygen sensors
- Check fuel trims and fuel pressure
- Compare upstream and downstream sensor behaviour
Generic OBD-II meaning. Manufacturer-specific meanings and checks can differ; always check the service information for the car.