P20F1
SCR NOx Pre-Catalyst Over Temperature (Bank 2)
SCR NOx Pre-Catalyst Over Temperature (Bank 2): the component is overheating, typically from extended load or slip.
- 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.
- Runaway regeneration upstreamCommon
Parts involved
- SCR Pre Catalyst
- Exhaust Temperature Sensor
P20F1 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.