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Old 01-12-2003, 11:58 PM   #3
Allergic to turbos
Member#: 181
Join Date: Aug 1999
Chapter/Region: MAIC
Location: MAIC & Southeast
Exclamation Re: P0420 Cat below efficiency

Originally posted by GreenGiant
I have a 2000 Legacy OBW Ltd. with 61K on the clock. My car is BONE STOCK as far as the engine is concerned. I got a P0420 "Cat. below efficiency threshold: bank 1". I was told by the AutoZone clerk that this is an O2 sensor going bad and I needed to replace the sensor. I have since been told by McDade and HndaTch627 that this is really my cat going bad. Updates to come.

P0420 - Cat. below efficiancey threshold: bank 1
I've had that twice. I had 49k on the clock. The dealer replaced the cat. 10k miles later, I've not seen that CE light.

Now I'm getting another code, P0065. I've had 6 CE lights since Thanksgiving.

A friend had the same code on his RS a few weeks ago. Turns out that a solenoid mounted on a bracket behind the power steering resivoir. I took it apart and cleaned it, seemed to work and the light was off, but as mentioned before, its back on. I also installed a Ganzflow intake at the same time and after 120 miles, I've got yet another CE light. I'll get it scanned tomorrow and post what it is.

BTW, the Ganzflow and K&N are my only modifications to the intake/fuel system.
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Last edited by munkis; 01-14-2003 at 10:27 PM.
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