P214C: SCR NOx Catalyst Outlet Temperature Too High

What does P214C mean?

P214C looks at the downstream end of the SCR catalyst: the temperature measured behind it rose above the permitted maximum outside regeneration. California's OBD rule lists SCR intake and outlet temperature as separate data values a diesel must report, so both points are watched on their own. An outlet reading that climbs above the inlet value hints at heat produced inside or just ahead of the brick, for instance hydrocarbons burning on the SCR or soot glowing in a combined filter-SCR unit, but a faulty outlet sensor is just as likely. The material limit is the same as on the inlet side, which 40 CFR 1036.115 and Navistar's patent US20190232224 describe for vanadium catalysts. No manufacturer documents P214C publicly. P214A is the inlet counterpart, P214D the outlet fault during regeneration.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light on
• Reduced engine power
• Implausible outlet temperature compared with the inlet value in live data

Common causes

• High SCR outlet temperature sensor faulty or reading too high
• Medium Hydrocarbons passing the oxidation catalyst and burning on the SCR
• Medium Fuel or oil entering the exhaust from the engine or turbocharger

Likelihood is a general estimate across vehicles; your make and model may differ.