P0420, could it not be the catalytic converter?

How old are the existing sensors, or were they also replaced with aftermarket parts?

 

So this cat on the car right now used to not have this code and no code and was working fine this aftermarket cat?

 

Oh and do you have any idea how long it was on the car working like weeks months

 

Sensors don't last forever, and if over 250km now might be a good time to replace the upstream sensor with OEM or Denso.

If the catalytic was stolen, they usually take one of the sensors with it.

 

The vibration from a sawzall might likely destroy an oxygen sensor.

 

How many kilometers are on the vehicle (or A/F sensor)?

The A/F sensor may have a short circuit, you can use the workup below to determine if it needs replacement.

Here is the workup for P2195 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Prius%20Service%20Manuals%202004/%E4%BF%AE%E7%90%86%E6%89%8B%E5%86%8C/04pruisr/05/2054m/cip2195.pdf

Here is the workup for P0420 : https://attachments.priuschat.com/attachment-files/2017/02/120177_p0420.pdf

 

I would try a different scantool app to confirm those A/F and O2 readings.

On my 2006 with 205k at steady cruise, A/F is around 3.3V, O2 is around 0.7V, short and long term fuel trims are 0 +/- 5%.

IF your A/F is actually near 4.0V and it's telling the truth, the engine is really lean- O2 should be near 0V and fuel trims should be high (+)%.

IF the A/F is actually near 4.0V but it's lying, the engine is really rich- O2 should be near 1.0V and fuel trims should be high (+)%.

IF fuel trims are near 0 and the O2 is moving (0.1V to 0.9V) then Torque is lying about the A/F value.


P0420:

NO exhaust leaks from the exhaust manifold to 18" past the O2 sensor (not even a pinhole)- I find only a dealer gasket will reliably seal the spring bolt joint at the manifold).

NO misfires, fuel trims near 0, A/F and O2 sensors can report "full rich to full lean".

No excessive oil burning (will "kill" the cat fairly quick).

If all that's ok, then I put a "good" cat in (preferably OE).

Posted via the PriusChat mobile app.

 

Please report back in this thread with any updates.

 

Thanks for the update.

Posted via the PriusChat mobile app.