P2097
Post Catalyst Fuel Trim System Too Rich (Bank 1)
Long-term post-catalyst fuel trim on bank 1 has reached its rich limit. The downstream sensor sees more reductant than expected, often pointing to a degraded catalyst that no longer stores oxygen, or a failing downstream sensor biased rich.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Symptoms
- Check engine light on
- Failed emissions inspection
- Possibly slightly increased fuel consumption
- Sulfur (rotten egg) smell from exhaust under load
Common causes
Ordered by how often each turns out to be the cause.
- Catalyst oxygen storage exhaustedCommon
- Downstream sensor biased richPossible
Parts involved
- Oxygen Sensor Downstream
- Catalytic Converter
P2097 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.