DTC Detection Logic

WARNING: This page is about a different car, the 2018 Nissan Titan XD. However, it is still accessible from the selected car via links, so may be relevant.

The Engine Control Module (ECM) calculated the DOC efficiency was less than required to successfully complete a regeneration.

DTC	CONSULT screen terms (Trouble diagnosis content)	DTC detection condition
P0420-00	CATALYST SYSTEM B1 (Catalyst System Efficiency Below Threshold)	1	Diagnosis condition	Engine is running and active regeneration of the after treatment diesel particulate filter is occurring.
			Signal (terminal)	(-)
			Threshold	Filtered value of hydrocarbon efficiency < 55% where hydrocarbon dosing efficiency is defined as DOC heat/DOC dosing heat
			Diagnosis delay time	Diagnostic runs continuously when the engine is running and active regeneration of the after treatment diesel particulate filter is occurring.
		2	Diagnosis condition	Engine is running and active regeneration of the after treatment diesel particulate filter is occurring.
			Signal (terminal)	(-)
			Threshold	DPF intake temperature - DOC intake temperature < 10°C
			Diagnosis delay time	Diagnostic runs continuously when the engine is running and active regeneration of the after treatment diesel particulate filter is occurring.