airmaui

iTrader: (1)

Hello,

First I'd like to thanks the folks on this great forum (especially VVTiBob and mandyfig) for providing me with assistance in resolving an issue I was having with my car.

For months my '03 with 90K miles was throwing +" P0420 code Catalyst System Efficiency Below Threshold (Bank 1) " errors. My local dealer and a respected repair shop stated it's the catalytic and must be replaced (at great expense!) I decided to first replace the driver side
O2 sensors one at a time. I replaced the upstream first with no change. I then replaced the downstream and it fixed the problem. It's been 4 months now and almost 4k miles. It was a bit of a problem changing the downstream sensor as the wires go thru the cabin. You must pull back the carpet to access the plug.

Thanks again for your help!

GS4_Fiend

iTrader: (22)

The post oxygen sensor is the one that monitors the cat. Glad you got it solved.