Dear Scotty. I have a 2011 Lexus ISF with 94,883 miles The check engine light came on it has a code of P0420 “catalyst system efficiency below threshold bank one. My scanner says the temperature on all 4 cats is was 1248 at the time the light came on. It also made the traction control light come on? Any idea what would cause this.
I have never seen temp sensors on a cat. I would verify that with contactless thermometer
Did you look under your car to see if the cat was stolen? Were there any mods done to it? Look for damage to the exhaust (leaks etc) or sensors and wires.
Your cats shouldn't be worn out at 94k, but if they are, and they're running hot, then you have engine problems like rich mixture or misfires.
troubleshooting p0420:
https://www.obd-codes.com/p0420
https://www.aa1car.com/library/converter.htm
https://www.youtube.com/watch?v=3nmzq7gZJ20
Car has a cat back exhaust on it. Was put on by previous owner. I noticed there may be a slight leak at one of the connections. Used a scan tool and the voltage reference at the o2 sensors seem to be close to the same. Could a slight exhaust leak after the cats cause this code.
Yes, if you open the link I provided, that's exactly what it says.
Thank you for the help.
Wow, Nice car!
