Thanks to everyone for the info above, I had the same issue on my 2006 Lexus IS350.I was preparing for the worst and taking it to a mechanic where I'm sure they would have replaced the Cat and O2 sensors.... I thought I would check under the hood at the mass flow..... the connector was not on all the way! plugged it in and fault was gone. hope this helps you guys.
P0420 - Catalyst System Efficiency Below Threshold Bank 1
in Lexus IS 250 / Lexus IS 250C Club / Lexus IS 220D & IS 200D Club
Posted
Thanks to everyone for the info above, I had the same issue on my 2006 Lexus IS350.I was preparing for the worst and taking it to a mechanic where I'm sure they would have replaced the Cat and O2 sensors.... I thought I would check under the hood at the mass flow..... the connector was not on all the way! plugged it in and fault was gone. hope this helps you guys.