Looking for some help.

I got code P0420 on 2009 IS250 AWD 92,000 miles. I used a infrared thermometer before and after catalytic converter and difference in temperature was normal around 90 degree difference hotter after cat. Both catalytic converters checked out okay as far as temperature. I also didn’t hear any rattling on the catalytic converter. I’m suspecting an o2 sensor. I checked for leaks and couldn’t find any under the heat shield. I uploaded a graph of the o2 sensors at around 2000 RPMs. Any help would be greatly appreciated.

 

I would still suspect an exhaust leak. Especially on the AWD's. Classic code for it, i'd have a exhaust shop take a look. I went through the same thing - was a leak at front of heat shield on midpipe.

 

Thank you for responding. The pipe does look corroded but I was unable to find any leaks. I’ll have to look closer.

 

EZLex is right. P0420 and P0430 on this car are typically caused by an exhaust leak on or near the Y-pipe. The reason for the code is that the OBD2 diagnostic for the catalytic converter efficiency runs just as the car hits operating temperature from a cold start, but on a car with a leak the loss of hot exhaust gasses delays the time it takes for the lightoff until after the test has run.

 

Thank you for responding and directing me to the leak. Both of you were correct and no codes in over a month since the leak was fixed. I appreciate your help!