P20ECSCR NOx Catalyst Over Temperature (Bank 1)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P20EC means the engine computer has registered a temperature in the SCR catalyst of bank 1 above the limit its washcoat can tolerate. The limit depends on the formulation: vanadium-based SCR material starts to sublimate irreversibly above roughly 550 °C, as Navistar's patent US20190232224 and the US rule 40 CFR 1036.115 both state, and US heavy-duty certification requires engine makers to protect such catalysts from high temperatures. Copper and iron zeolites tolerate more. No manufacturer documents P20EC publicly with thresholds; Ford's 2023 diesels, for example, report aftertreatment overheating as P200C/P200E. Typical triggers are an uncontrolled exotherm during filter regeneration, fuel or oil reaching the exhaust, or a faulty temperature sensor. The code warns of possible lasting damage, so a later P20EE is a common follow-up.
- What you may notice
- Malfunction indicator lamp on
- Regeneration interrupted or power reduced to protect the aftertreatment
- Later loss of NOx conversion (follow-up code P20EE)
- Likely causes
- LikelyExcess heat release during particulate filter regeneration
- PossibleUnburnt fuel or oil reaching the exhaust (leaking injector, turbo seal)
- PossibleSCR temperature sensor reading too high
- RareRegeneration or thermal-management calibration needing an update
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €3,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.