DTC Detection Logic

The ECM monitors the switching frequency ratio of air fuel ratio (A/F) sensor 1 and heated oxygen sensor 2.

Courtesy of NISSAN NORTH AMERICA, INC.

A three way catalyst (manifold) with high oxygen storage capacity will indicate a low switching frequency of heated oxygen sensor 2. As oxygen storage capacity decreases, the heated oxygen sensor 2 switching frequency will increase.

When the frequency ratio of A/F sensor 1 and heated oxygen sensor 2 approaches a specified limit value, the three way catalyst (manifold) malfunction is diagnosed.

Three way catalyst (manifold) does not operate properly.
Three way catalyst (manifold) does not have enough oxygen storage capacity.

DTC	CONSULT screen terms (Trouble diagnosis content)	DTC detection condition
P0420	TW CATALYST SYS-B1 (Catalyst system efficiency below threshold bank 1)	1	Diagnosis condition	-
			Signal (terminal)	-
			Threshold	Three way catalyst (manifold) does not operate properly
			Diagnosis delay time	-
		2	Diagnosis condition	-
			Signal (terminal)	-
			Threshold	Three way catalyst (manifold) does not have enough oxygen storage capacity
			Diagnosis delay time	-
P0430	TW CATALYST SYS-B2 (Catalyst system efficiency below threshold bank 2)	1	Diagnosis condition	-
			Signal (terminal)	-
			Threshold	Three way catalyst (manifold) does not operate properly
			Diagnosis delay time	-
		2	Diagnosis condition	-
			Signal (terminal)	-
			Threshold	Three way catalyst (manifold) does not have enough oxygen storage capacity
			Diagnosis delay time	-