P0420

P0420, P0430 THREE WAY CATALYST FUNCTION

DTC 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.






DTC CONFIRMATION PROCEDURE

Step 1-3:

Step 3 (Continued)-7:

Component Function Check

Step 1:

Diagnosis Procedure

Step 1-5:

Step 5 (Continued)-7:

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