Honda Civic oxygen sensor?

I don't know the code but I was told it was the O2 sensor bank 1 sensor 1. I was also told that I should replace 2 and not just the 1 it tells me to. I Also need to know which sensor I need. The bank 1 sensor 1 is Denso 234-9005 I believe but I would like to be sure. My car is a 2004 Honda Civic LX.
So my questions are as follows:
1. Do I need to replace two sensors or just the one it showed on the code reader?
2. If so, should I replace bank 1 sensor 2?
3. Is Denso 234-9005 the oxygen sensor I need for the first sensor?
4. If I need to replace a second sensor like the guy said I should do, what is the name of the part?

OBD codes tell you the CIRCUIT is bad. Check the wiring and connector first. And confirm reference voltage if possible. Sensor 1 is Upstream or Pre Cat. Sensor 2 is Downstream or Post Cat. Banks refer to V engines not Inline like yours. If the circuit is good on Sensor 2 there's no sense in changing it. You can look up your own parts, can't you? Denso is a good brand but hardly the only one. Just look at your plug and make sure it's the same.

  • Help me! Code P2A00 Oxygen sensor circuit range/performance bank 1 Sensor 1 2008 honda Crv ex? I have an 2008 Honda crv Ex and this code came up "Code "P2A00" Oxygen sensor circuit range/performance bank 1 Sensor 1 i want to replace it myself because i know its simple and the dealer wants to charge me over $300 and i can do it for half the cost when i looked it, it has two sensors together one closer to the engine and the other a bit more behind it i don't know with of the two it is.
  • Does a 99 Honda CR-V have and up and downstream oxygen sensors? My check engine light came on, took it in to O'Reily's, and they say I need a new O2 sensor. They can't tell me if it is up or downstream though so I'm wondering if the 99 CR-V only has one.
  • Oxygen sensor original colour code? What's the original colour code for a 2001 honda civic (hatchback) trying to remove the engine check light, tried a few oxygen sensors but can't seem to get any luck
  • Honda civic code PO135 won't turn off with new o2 sensor? Code reader said po135 which means O2 Sensor Heater Circuit Malfunction. Bought a new o2 sensor, changed it and then reset the dash board. The light stayed off while the car idled but came back on when I drove it with the same code. Someone on youtube said that if it doesn't idle properly, you probably have a dirty aic valve and that could be what is causing the o2 sensor not to work. The car idled fine but I tried cleaning it anyways, the same thing happened. Someone please help!