P20F3
SCR NOx Pre-Catalyst Efficiency Below Threshold (Bank 2)
SCR NOx Pre-Catalyst Efficiency Below Threshold (Bank 2): the control module has detected this fault condition.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: hard
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.
- Pre-catalyst thermally agedCommon
Parts involved
- SCR Pre Catalyst
P20F3 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.