P0420 Toyota -

Question

I have a 2001 Toyota Tacoma 2.4 Ltr. 420 codes showed cat conv. Replaced both converters with after market and the same 420code came back up. Old converters looked fine. Code also shows O2 sensors are fine.

What else could it be? Thanks,

Answer 1

P0420 Catalytic system below threshold

Worn sparkplugs can contribute to a P0420 , false air from the MAF (mass air flow) air duct ,check the air duct of the MAF Here is a torn  air duct that gave a P0420 and a P0171 (lean condition) with no noticable drivability condition just a CK ENG LT.