Rick's Free Auto Repair Advice

Posts Tagged: P0420 code

P0420 caused by bad O2 sensor?

P0420 can it be caused by a bad O2 sensor? Does a bad oxygen sensor cause a P0420 code? Answer: Rarely, but it depends on the vehicle On many pre-1996 vehicles the upstream oxygen sensor uses a “narrow band” type sensor, and post 1996 vehicles often use this type of sensor as the downsteam sensors. These sensors compare the amount of oxygen in the exhaust to the amount of oxygen in the outside air. It obtains and ambient sample through one of the wires (between the copper and the insulation). … Read More


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