[Idahome]

Originally Posted by Idahome

My check engine light came on today, diagnostic device gave a P0420 Catalyst System Efficiency Below Threshold (Bank #1). I've got 140,000 on the RAV. All written indicators tell me either O2 sensor or Cat, is there a easy/cheap way to determine exactly what it is before I put out the cash to fix it? One thing I've noticed is the fuel efficiency seems to have gone down quite a bit.

Thanks

I'm going to start with replacing the inexpensive stuff first but I can only find 1 O2 sensor on my exhaust system. The one I found is down stream of the catylatic converter, does anyone know where the other one is? My Haynes manual show 2 sensors but not in the place they're actually at. Also, does anyone have a good way to get the rusted nuts undone? I sprayed penatrant on them and they still won't budge.

Thanks