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Home >> Infiniti >> 2014 >> Q50 Base, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - DTCS P0171 To P0463 (Except Hybrid) >> DTC P0420, P0430: Three Way Catalyst Function >> DTC Description >> DTC Detection Logic

DTC Detection Logic

The ECM monitors the switching frequency ratio of air fuel ratio (A/F) sensor 1 and heated oxygen sensor 2. A three way catalyst 1 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 1 malfunction is diagnosed.

Fig 1: Three Way Catalyst Function Operation Diagram
G09160107Courtesy of NISSAN NORTH AMERICA, INC.
DTC DETECTION CONDITION

DTC No. CONSULT screen terms (Trouble diagnosis content) DTC detecting condition
P0420 TW CATALYST SYS-B1 (Catalyst system efficiency below threshold bank 1)
  • Three way catalyst (manifold) does not operate properly.
  • Three way catalyst (manifold) does not have enough oxygen storage capacity.
P0430 TW CATALYST SYS-B2 (Catalyst system efficiency below threshold bank 2)
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