Intermittent p0420 - Cat efficiency issues

Lab scope would be the ultimate tool to monitor the post sensor. If your scan tool has the ability to read the sensor PID, it would be the easy way to go. A scan tool with sensor graph output would be similar to the labs scope without the need to access the circuit under the vehicle
Yes, you're looking for low sensor activity. The more the sensor switches, the less effective the converter is at storing the needed oxygen.

 

I don't know if it's easier because you'll need to access the ECM. I like to test at the sensor just in case you have a circuit problem. I always look at interpreted data with a scan tool and monitor the sensor at the plug by back-probing the connector. If I have a problem child, I'll monitor all 3 places

 

I just thought I'd chip in here... I get P0420 which is cleared with the OBD. It comes on after the ECU has been through it's emissions checks when you're above the trigger speed. So if you never get to this speed / temperature where the ECU can do the checks, your EML will not come on.

My voltage trace for the downstream sensor is fine, and the A/F mix sensor also fine. I suspect the issue is the fact that I grounded out on the road a year back and the post-sensor is so low down, it got knocked. I can certainly feel play in the sensor when I wiggle it. Needless to say it's on my list of things to sort. BTW, I have 149,000 miles and running fine.

 

It will not pass emission test if the sensor check is not completed.

 

Just wanted to ask if your Prius is using any oil? This can be a reason for a CC to fail by the oil coming through the exhaust and clogging the CC. This has been my experience in my 2008 Prius.

 

I have a CE light with p0420. Just yesterday I noticed significant performance issue. I can't accelerate quickly...otherwise I get jerky acceleration...loss of power. So I have to very gradually press gas pedal.
Guessing CAT is clogged. Added duralube cat cleaner yesterday and drove on highway for 35 miles. The CE light is still on and jerky acceleration/ performance issue persist. I have added half of cat cleaner and remainder will add when I fill gas next.

Any suggestions here on jerky acceleration and performance issue. I have had p0420 come on intermittently in the past 15k miles. However it's been on permanently the last 1k mile.

Changed spark plugs, pcv valve, vcg gasket. 250k miles on 2007 Prius. Consumes 1quart after 1200miles. So I top it off once between every oil change after 2700 miles

 

Change the cat with the $600 to $700 version from NapaAuto Parts. Works fine with no codes. Sell the oem cat for much of the replacement part cost.

 

I was thinking $279
Walker Exhaust Ultra EPA 16337 Direct Fit Catalytic Converter


Btw is RRCats a reputable place to sell the original cat ? I am guessing I may get around $1000 for the 2 cats in Prius.


Just concerned about the performance issue I am facing. Hopefully it's just the cat that is causing the performance issue. Mpg also has dropped from 43 to 40.