P0420

I have a 2006 Tacoma I am working on for a friend. 2.7l 4x2. automatic.
It has a P0420 code and the b1s2 was at 0.0v according to the computer. I tested it with a torch and multimeter, And it was dead. Replaced with a new denso unit and still have 0.0v. So I removed and tested the new unit and it went up to 1.0v. Before i replaced it I used a aaa battery and tested the wires and got the same battery voltage at the computer reading of 1.2v. Does anyone have any idea what my next step will be to figure this out?

 

How long did you run the truck?

The ECM won't turn the downstream heater on until the truck has ran for 5-10 min.

 

If you don’t live in a place that does emissions testing.

I’d just ignore p420. I have it in my truck and I just clear the code when it shows.