Help with P0420

Hello,

Was about to take my Prius for inspection in NJ after replacing the three way valve (sorry if that's not the name) that routes coolant. I had a check engine light on for over 6 months, but in NJ, you have to remove that even if not emissions related. Replaced the part, cleared the code... after driving a little while ... new code P0420. Darn.

My Prius has 210K miles... I know that's a lot, but it is not an oil burner. Before doing anything drastic I would like to check some of the basics, like cleaning the MAF, verifying O2 sensor readings and anything else the forum members would suggest. I don't have a lot of diagnostic tools, but I do have a cell phone, an OBDII reader and the Torque app.

So first off, probably everythings original in the exhaust. Cat failure at 210K common?

Any suggestions going forward?

My next plan is to clean the MAF and keep driving.

Thanks!

 

That's interesting. I know the replacements don't have as much or the same catalyst. Kind of makes sense that maybe I don't need another 200K miles on a replacement. I have been burned by replacements. I put one in my Accord years ago that was a name brand and the CEL persisted. Could have been due to some other factor.

I am going to keep your idea in mind and consider that if I can't get through inspection some other way. For now I sprayed the MAF sensor and am going to see if that helps.

I did noticed on torque that there was only one O2 sensor reading. I should have two on a prius right? one forward and one rearward of the cat?

 

I am using the torque app that can show 8 o2 sensor readings. Only one, O2 1x2, has a reading. The reading for O2 1x1 is empty. Is that the upstream sensor? Also the OBDII monitor for O2 Sensor is marked as incomplete

 

Thanks for that advice. I have an older copy of Pro on a tablet. Going to connect that and measure O2 and fuel trims and post those here.

 

I took a drive with Torque Pro and the O2 sensors appeared to be in the ranges mentioned, with one small exception. The front sensor looked like it snapped to 5.0v on release of the throttle, and then went back to normal values.

I did notice that the final O2 sensor monitor completed and the check engine light disappeared. I was able to take it to inspection where it passed. two more years to not have to worry. Fuel economy is reasonable 45-48 but not incredible. battery voltages appears to be even across all the cells... seem to max out around 17+ V.

I would like to know more about the catalytic converter issues. Is there something special about the Prius compared to other vehicles or is any car or truck in the last 30 years with factory exhaust a candidate for theft. I have a 99 Ford ranger with California emissions and that would be a lot easier to get under.

I have also noticed there is a manufacturer that sells metal plates to cover your exhaust and keep thieves away. I wonder what the NJ inspection with their cameras under the vehicle would think about those.

Thanks

 

Well... you called it. I parked my car in a Extended Stay America hotel in Elizabeth NJ and went on an extended vacation. When I got back, my cat was stolen. The car was parked in a fenced lot, but what does that really mean? I filed a police and incident report, but not sure anything will come of it.

Also, the cuts they made were beyond the flanges on both sides of the Cat. This means both the exhaust header and the exhaust pipe behind the Cat were damaged.

 

OK.. I am an idiot. I looked at the factory part and it runs from the exhaust manifold flange all the way to near the back axle and includes the catalytic converter, oxygen sensor and silencer.

The cut on my exhaust was after the oxygen sensor and between the second cat and the silencer. In other words, half my cat was stolen and I still have the oxygen sensor. Maybe that's why I didn't get a check engine light while driving.

Toyota's estimate to fix this... $2700, but an aftermarket unit and a gasket might get the job done.

There must be some value to the first cat and if you still have your contact, I may be able to get some $$ back for that part.



Thanks.

 

What makes me happy is that the thief didn't get all of the prize. Bastard. The street value for an aftermarket must be pocket change, but I guess once you are under there, you just remove it anyway. I guess I have to consider putting in a plate of some sort. Maybe do the equivalent of an electric fence wire.

If you have time....
Can you provide me the contact info for the cat buyer in TX you had mentioned in an earlier thread?
What aftermarket did you go with and has it been keeping the CEL off?

For aftermarket I see some starting at $150 that fit over the old exhaust pipe to ones that are name brand for $300 or more

Thanks.

 

Thanks TMR-JWAP for your help.

For anyone reading, it helps to understand the motivation for people to steal these converters. At the current price of scrap metals, the converters have a scrap value well over $1000. Aftermarket replacements do not have the need to meet the original high standards that Toyota's parts did (except for California). Aftermarket units will meet the emissions standards of most states and can be purchased for $150-300.

Stealing a Prius catalytic converter is a relatively easy task. It doesn't take a competent thief much more than a few minutes to raise your car and remove the exhaust.

On a side note, if you get your catalytic converter replaced because you suspect its not getting the job done, you also have the right to ask for and recycle your old OEM part... otherwise your mechanic will do it

 

I can’t say what my normal O2 readings are without putting in the OBDII tool but I can say my check engine may very well have been from an exhaust leak from deteriorated gasket between the exhaust manifold and catalytic converter. It was original with 200k+ miles
The cel has been off since the gasket was replaced. The catalyst monitor was pretty quick to be satisfied with one or two short trips. Trip required exhaust to reach normal operating temperature.
Do you have a CEL?