2006 Prius P0420 Code..???

I wouldn't say that it is normal to have a catalytic converter issue on your car at 103K miles, but it's not unheard of either.

If the code returns, I'd suggest replacing the air/fuel ratio sensor upstream of the catalytic converter first. Maybe that will avoid the need to replace the cat.

Good luck.

 

Re: 2006 Prius P0420 Code

Our 2006 Prius had the code P0420 come up on my code reader. I reset the code and drove a few more miles and the "check engine light" came on again.

I took the car to the dealer (since we have a full warranty to 100k) and they said a different code for emissions canister came on. They tried to tell me I may have left the gas cap on loose. I have never done this. I tried to explain to them that my code reader read P0420 and P0420 (pd).

Anyhow, I picked-up the car. Mechanics left grease marks on my center console arm rest, rocker panel plastic piece, and driver's door arm rest! Man, that pissed me off. They tried to clean it up at the detail shop and made it worse. They had to send it out to be professionally cleaned.

Then, less than 5 miles from the dealer, check engine light came on again.

My code reader read P0420. I had to take more time off work to go back to the dealer. At 77,736 got a new catalytic converter put on under warranty(80k emissions factory warranty). At least I didn't have to pay over $2,000 for a new one.

The dealer experience wasn't great. This is why I try to do all the servicing of the car myself.

 

As I understand it, catalysts are damaged by overheating, but this generally only happens if completely unburnt fuel gets to it (which then flames up). This can happen with misfires but the car is also checking for those. It can also be damaged by excess sulphur in the fuel - the sulphur winds up coating the surfaces. If you've only used very cheap fuel in the car I suppose this could happen, but generally sulphur levels in fuel are kept very low to avoid these problems.

P0420 is signalled if, after comparing the pre- and post-treatment sensors, the post-treatment sensor shows that the oxygen stripped from the NOx when running lean went straight up the exhaust pipe, rather than being stored on the catalyst surface for a short period, where it's used to combine with CO (to form CO2) and burn off hydrocarbons (to form water and CO2), when running rich.

If it's reported, there's an engine test cycle to run to confirm that the code re-occurs, and another cycle to run while watching the voltages of the sensors, where the engine speed is changed rapidly over a few seconds. If the sensor values are in range and show that the output oxygen level doesn't change significantly, the catalyst and sensors are working and the ECU is bad. If the values are in range but the post-treatment sensor is oscillating wildly, the catalyst is bad. If the sensor values are out of range the sensor(s) is/are bad. It's also possible that exhaust gas is escaping up-stream from the catalyst and that's why the sensor values are wrong.

Looks like it should take about an hour to diagnose?