Check engine code!!

[whitey]

My check engine light came on and i took my car to autozone and advance auto, their code checker came up with, bad catalyst left bank!so im thinking its either a bad O2 sensor or clogged cat. My friend who also has a 240 says that their is 2, O2 sensors behind the cat. I would like to know if i can remove my cat and not mess up the readings for those 2 sensors. I just bought the car so im not to familiar with it.its a 95 240sx

[574-240sx]

I'm in Granger a few miles from you I can probably help you out I have the same problem with my 95 currently too. I know I need to change my o2 sensors forgot which one. email me at [email protected]

Nick

[DAEDALUS]

I'm pretty sure it's 1 before and 1 after the cat. If you remove the cat, you could, in addition to breaking federal law, trigger the same code indefinitely. The 2nd sensor is there to tell the ECU how good a job the cat is doing. Take the cat away, and the ECU will think the cat is broken and throw a code.A clogged cat would show up on a vacuum test. A vacuum test is quick and it tells a lot about an engine.

[whitey]

well if i take the cat off, the first o2 shouldnt be affected. As far as the second one, a friend told me about these fake o2 sensors that take place of an o2 just to give the computer a reading. Another friend told me that he took his second one out and tied it in with the first o2, that was on a mazda rx7. Im not worried about the LAW, with all the loud *** hondas running around here, I think im safe.

But i dont wana take it off if its gunna mess with my ecu readings. I was hoping someone on this site has takin their cat off before.

Shouldnt taking the cat off also create more flow?

[DAEDALUS]

Most 240s don't have a 2nd O2 sensor. It doesn't do anything to actually reduce emissions, it's only function is to tell on a bad cat. Part of the OBDII emission requirements that became mandatory in the US in '96 model year. Tying the 2nd harness to the 1st sensor doesn't sound right to me--wouldn't the ECU think the cat wasn't doing anything?

[whitey]

with that being said, only having one o2 should allow me to remove it and be fine, right?

[DAEDALUS]

??? But your car does have 2 sensors, does it not? Not sure what you mean by "fine". Clogged cats are really rare. Is there anything wrong with the way it runs, besides the CEL? Make sure first--why pollute and break the law if there's no real benefit? Do a 2-minute manifold vacuum test to see if it's clogged.