DTC P0421 & DTC P0431: Notes

Code Definition

DTC P0421: Catalyst Circuit Malfunction (Bank 1)
DTC P0431: Catalyst Circuit Malfunction (Bank 2)

NOTE: Before performing any diagnostic test, refer toWARNINGS, CAUTIONS and NOTES in DIAGNOSTIC TESTS .

NOTE: Testing individual components does not isolate shorts or opens. Perform all voltage tests using a Digital Volt-Ohmmeter Meter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate wiring harness shorts or opens.