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Home >> Infiniti >> 2013 >> M56 Sport >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - DTCS P0190 To P1084 >> DTC P0420, P0430: Three Way Catalyst Function >> DTC Logic >> DTC Detection Logic
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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 (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.

Fig 1: Three Way Catalyst Operation Diagram
G08897172Courtesy of NISSAN NORTH AMERICA, INC.
DTC No. Trouble diagnosis name (Trouble diagnosis content) DTC detecting condition Possible cause
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.
  • Three way catalyst (manifold)
  • Exhaust tube
  • Intake air leakage
  • Fuel injector
  • Fuel injector leakage
  • Spark plug
  • Improper ignition timing
P0430 TW CATALYST SYS-B2 [Catalyst system efficiency below threshold (bank 2)]
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