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 (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.

DTC Confirmation Procedure

Step 1-3:

Step 3 (Continued)-7:

Component Function Check

Step 1:

Diagnostic Procedure

Step 1-5:

Step 6-8:

Step 8 (Continued)-11: