2002 Ford Taurus O2 sensors

TONYDERISE

MEMBER
2002 FORD TAURUS
6 CYL
FWD
AUTOMATIC
210,000 MILES

The check engine light is on. The troubleshooting code says -catalyst efficiency low bank 1, I believe the 02 sensors may be bad. Troubleshooting code is P0420. Where can I find the 02 sensors so that I can attempt to change them myself and save a little money. Any help would greatly be appreciated. Thank you.

1 Reply

CARADIODOC

MECHANIC
33,741 POSTS

P0420 - Catalyst System Efficiency Below Threshold (Bank 1)

The O2 sensors aren't the problem. The fault code is based on the readings of the sensor after the catalytic converter. That's How the Engine Computer determined there was a problem. You don't kill the messenger because you don't like the message.

The cause of this code is typically the catalytic converter. You can verify that by watching the switching rates of the front and rear sensors. The front one will switch between rich and lean about twice per second. The rear one should switch less than once per minute. When the rear one switches just as fast as the front one, it's because they're seeing the same exhaust gas composition, meaning no change is taking place in the converter.