How to Diagnose a bad Catalytic Converter on Toyota and Lexus

A Toyota master diagnostic technician shares tips on how to diagnose a bad catalytic converter P0420 and P0430 and addresses common misconceptions.

In this video I am continuing on my series on how Toyota engine control works. If you are just stopping by this video, catch up on the rest of the series here:
   • Toyota Engine Controls  

In this video I will start with the beginning of catalytic converters, what their primary function is in simple terms.

Starting with diagnosis I didn't want to make a conventional video that's usually available on YouTube. I wanted to share information that is otherwise not very available mainly on the newer car tests and how the OBD2 system runs a secondary test to check the O2 sensors.

I shared a graph on this video of both sensor 1 and sensor 2 in this video which is a good reference for a good catalytic converter. You always want to see your 2nd sensor not following the pulses of the 1st sensor.

Common things that would lead to a false P0420 or P0430 are exhaust leaks between the exhaust manifold and the 2nd sensor on the exhaust. A common method to check the exhaust is to block the exhaust using a shop towel and that will immediately show you any small leaks on the exhaust that you otherwise can't hear because of the loud noise of the engine running.

I also cover the unfortunate catalytic converter thefts and make some recommendations on how to prevent catalytic converter thefts in your car if you live in an area with an increased theft rate. I hope you never have to go through the hassle of having your catalytic converter stolen because it is really a headache to deal with insurance and police over this matter. No one is exempt from these shameful thefts. The most recent theft that I've seen that's becoming famous is our fellow Professional mechanic and awesome YouTuber ‪@ericthecarguy‬ Check out this video if you're interested to see how these shameful thieves do their horrible act:
   • This Guy Stole My Catalytic Converter!  

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0:00 Intro
0:37 What do Cats do?
2:08 Diagnosis
17:01 Catalytic Converter Thefts