DTC P0420 (Cat) - Catalyst System Efficiency Below Threshold

NOTE: Refer to illustration for connector and terminal identification. See Figure -Figure .

With SSM or OBD-II scan tool, check for DTC P0130, P0133, P0135, P0136, P0139 and P0141. If any DTC is found, repair as necessary and retest. If no DTC is found, go to next step.
Check for gas leaks or air suction caused by loose or missing nuts and bolts, or damage to exhaust system. Check especially between cylinder head and front exhaust pipe, between front exhaust pipe and front catalytic converter, and between front and rear catalytic converter. If damage is found, repair or replace exhaust system. If no damage is found, go to step 3).
Separate rear catalytic converter from exhaust pipe. If there is damage at rear face of rear catalytic converter, replace front and rear catalytic converters. If there is no damage to rear converter, remove front catalytic converter. If there is damage to front or rear face of front catalytic converter, replace converter.