P0420

P0420 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 1-2:

Step 2 (Continued):

Diagnostic Procedure

Step 1-4:

Step 4 (Continued)-6:

Step 7-11: