P2C7A
SCR NOx Catalyst Efficiency Below Threshold Bank 1 Catalyst 2
The ECM detects that the conversion efficiency of the second SCR catalyst on bank 1 is below the calibrated threshold. NOx slip past catalyst 2 is too high.
- 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.
- Catalyst 2 aged or contaminatedCommon
- Reductant dosing insufficient for cat 2Possible
Parts involved
- SCR Catalyst B1 Cat2
- Reductant Dosing Unit
P2C7A 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.