Powertrain, generic (extended)

P20EC SCR NOx Catalyst Over Temperature (Bank 1)

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Excess heat release during particulate filter regeneration
Unburnt fuel or oil reaching the exhaust (leaking injector, turbo seal)
SCR temperature sensor reading too high
Regeneration or thermal-management calibration needing an update

Symptoms

  • Malfunction indicator lamp on
  • Regeneration interrupted or power reduced to protect the aftertreatment
  • Later loss of NOx conversion (follow-up code P20EE)

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–3,000
Time1–5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

scr catalystexhaust gas temperature sensor

Related codes

P20EDP20F0P20EEP200CP200EP2428

References: law.cornell.edu, patents.google.com, fordservicecontent.com.