gw204

I currently have (among other codes) a P0420 - Catalyst System Efficiency Below Threshold (Bank 1) code on my '01 ES300. As I was under the car looking at the cats I noticed that there is only 1 downstream AFR/O2 sensor. With that in mind, how is the obd2 system able to determine that it's bank 1 that's bad since exhaust gasses from both banks have mixed at that point in the exhaust?

That being said, I suspect that all 3 cats in the car are actually bad. I shot the inlet and outlet of each one with an IR gun and all three were warmer at the inlet than at the outlet...which from what I've gathered is the exact opposite of what I should see. :-/

Thanks.

Arsenii

Hello,

There are three A/F sensors in the car - Bank 2 Sensor 1, Bank 1 Sensor 1 and Bank 1 Sensor 2. Bank 2 Sensor 1 is located on the front of the engine, Bank 1 Sensor 1 is behind the engine, and Bank 1 Sensor 2 is exactly the one that gives you your headache. Bank 1 Sensor 2 is just a name to distinguish it from other sensors, it does not necessarily mean that the reason for your code lies exactly in the first bank, it means that either the sensor itself malfunctions, or your third catalyst is bad (or all catalysts for that matter).
It seems like your catalysts are just clogged.. If you really want to, you can remove the third one and take a look inside, that will definitely tell if something is wrong (I doubt that you will be able to do so though, since it is probably rusted shut)..

Hope this helps and best of luck!

gw204

Thanks for the info. That certainly makes more sense.

I got under the car a few weeks ago and shot each cat with an IR gun. Each one was roughly 100 degrees hotter on the INLET side. That tells me that all 3 cats are bad. The bank 1 cat even had a dent in it. It didn't look fresh so I can't really say how long it's been there.

Anyway, took it to a mechanic to validate my suspicions and he reported that the dented cat was bad...and he said a smoke test confirmed that I also need a vapor canister to address a P0446 code. Quoted me $1675 for the repair. I didn't ask if that was using aftermarket or OEM parts since I have no intention of spending that much on it. Car has over 230K so if it gets repaired I will be doing the work myself.

Since I don't have the smoke tester or other equipment to toggle the various evap valves on/off and watch pressures I figured $150 for the diagnostic fee was better spent than just firing the parts cannon.

gw204

I'm hoping I can pick up a used cat somewhere but in case that doesn't pan out, has anyone ever attempted cutting out the cat and welding a universal replacement in? I'm not spending the money on a new OEM one and reviews of the aftermarket ones seem dismal at best.