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.

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DTC No.
Trouble diagnosis name
DTC detecting condition
Possible cause
P0420
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 leaks
  • Fuel injector
  • Fuel injector leaks
  • Spark plug
  • Improper ignition timing
P0430
Catalyst system efficiency below threshold (bank 2)

 
 DTC CONFIRMATION PROCEDURE

 
 1.INSPECTION START
 
 2.PRECONDITIONING
 
 3.PERFORM DTC CONFIRMATION PROCEDURE-I
 
 4.PERFORM DTC CONFIRMATION PROCEDURE-II
 
 5.PERFORM DTC CONFIRMATION PROCEDURE AGAIN
 
 6.PERFORM DTC CONFIRMATION PROCEDURE-III
 
 7.PERFORM COMPONENT FUNCTION CHECK