Fault Family System: Powertrain (P-Codes) 9 SAE Codes

SCR NOx Catalyst Temperature

Diagnostic & Technical Explanation

P20EC (SCR NOx Catalyst - Over Temperature Bank 1) is a thermal-protection fault raised when the exhaust gas temperature sensor ahead of or behind the SCR catalyst (or its upstream pre-catalyst brick) reads outside the safe operating window, most often during an aggressive particulate filter regeneration event. Excess fuel dosed for regeneration, a partially restricted catalyst concentrating exhaust heat, and a temperature sensor reading falsely are the usual causes, and repeated over-temperature events can permanently damage the catalyst washcoat.

These 9 diagnostic trouble codes share one detection mechanism and one repair path, which is why MechanicDB groups them into a single authored fault family rather than repeating the same explanation 9 times.

Codes in this family (9)

Code	Definition	Repair coverage
P20EC	SCR NOx Catalyst - Over Temperature Bank 1	4 ranked fixes
P20ED	SCR NOx Pre-Catalyst - Over Temperature Bank 1	4 ranked fixes
P20F0	SCR NOx Catalyst - Over Temperature Bank 2	4 ranked fixes
P20F1	SCR NOx Pre-Catalyst - Over Temperature Bank 2	4 ranked fixes
P214A	SCR NOx Catalyst Inlet Temperature Too High	4 ranked fixes
P214B	SCR NOx Catalyst Inlet Temperature Too High During Particulate Filter Regeneration	4 ranked fixes
P214C	SCR NOx Catalyst Outlet Temperature Too High	4 ranked fixes
P214D	SCR NOx Catalyst Outlet Temperature Too High During Particulate Filter Regeneration	4 ranked fixes
P22FF	SCR NOx Catalyst Inlet Temperature Too Low	4 ranked fixes

What this page does not show

This page publishes the fault mechanism and the code index. The licensed dataset adds, for every one of the 15,886 codes, the full authored repair set (56,729 procedures in total) with the fields deliberately withheld here:

Procedures 2..n after the first-listed procedure
Aftermarket parts cost ranges in USD (est_parts_cost_min/max_usd)
Professional labor-hour estimates (est_labor_hours)
Step-by-step diagnostic and repair instructions
Replacement-part mappings and catalog lookups
6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)

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