Cold Start SCR NOx Catalyst Inlet Temperature Too Low
Same as P22FF but specifically during the cold-start window - the SCR catalyst inlet temperature does not reach the threshold needed for NOx reduction in the cold-start phase, so reductant injection cannot be enabled.
Affected components
- Scr inlet temperature sensor
- Scr catalyst
- Exhaust heat management
Common causes
- High likelihood: Heat-up strategy not bringing exhaust to temp
Possible symptoms
- Check engine light on
- Failed emissions inspection
- Possibly slightly increased fuel consumption
- Sulfur (rotten egg) smell from exhaust under load
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.