Apparently 04-05 EX Civics have an air-fuel ratio sensor already installed on them.
But 2001-03 Civics don't.
My ride: 2002 Honda Civic Coupe LX

I found an affordable, (random), 50.00$ Air/fuel ratio sensor from a local store nearby and what I'm wondering is;

1) Can I install this?
2) How do I install this? (for the purpose of installing a air-fuel ratio wideband gauge within the very same day. This is why I'm doing this)

https://shop.advanceautoparts.com/p/bosch-wide-band-oxygen-sensor-17212/10593547-p?c3ch=PLA&c3nid=10593547-P&c3apidt=21900173680

 

That's not true. The primary and secondary oxygen sensors are present in all 2001-2005 Civics. Whether you have an EX (Canadian Si) or not, dictates where they are located... but they all have them.

On your car, your secondary oxygen sensor (where you want to draw from for a/f ratio) is number 8 in this diagram:

 

Supposedly the 2nd oxygen sensor on the 04's and 05's is actually an air-fuel ratio sensor, rather than a regular o2 sensor is what I meant. I could be wrong but I did encounter about two people referring to this same problem.

Are you saying that #8 on the diagram is an Air-Fuel ratio sensor and that my car actually *does* have one? *.* @_@ <3

If so, you're the king.

 

The part design was changed from a narrowband Oxygen Sensor to a wideband, if that's what you're referring to. If you plan on swapping to a wideband, get prepared to do some work... and get out your wallet, because some added costs will be accrued (mainly K-Pro will be necessary to read the signal).
Here's a good guide on swapping up from 01-03 (narrowband) to 04-05 (wideband): https://www.civicforums.com/forums/1...-use-only.html

If you're looking to add a third sensor, you'll need to drill a hole in your exhaust piping, weld a bung onto the piping, and then wire it in.

 

Okay. That makes sense. I'm thinking about going with this then instead, I read the FAQ and installation guide, it looks like it might work plug n play for my car.

http://www.innovatemotorsports.com/products/MTXL.php

Do you think that is a good choice? I'd probably install the sensor it comes with into the location it specifies, unless you think one of my O2 sensors would be compatible? (thus making things simple).
Ultimately, I'm just looking for a good AFR gauge that's within a 120-200$ price range, if you know of any recommendations. Thanks

 

You can't run a wideband on your stock ECU, and if you want a wideband... neither of your stock ones qualify for the job as they're both narrowband.

 

Alrightythen.
Do you think that's a good price, for a AFR wideband Sensor + AFR wideband Gauge Combination? Do you think that kit would offer what I'm looking for? Sorry for all the questions. It's just, 200$ is a pretty lot of money for me! so I'm really hoping for someone's help along with finding the proper AFR gauge readout equipment.

 

If you are wanting to actively monitor a/f ratio without messing with any of the stock components (aftermarket ecu, etc...) you just need a wideband a/f kit, gauge sensor, wiring. Besides adding another O2 bung in you exhaust it basically just needs power & ground. They can be run independently of your stock O2 sensors and ecu. Basically what toyomatt84 said in post #4.

I personally have a PLX M300 Tuner Edition Wideband set up on my 99 Si (I realize this is a different car), I run it independently of my narrowband stock O2 sensor, but I am also using Hondata S300, so I have a wire from my wideband linked into my ecu so it can be monitored via the provided gauge and through the ecu on my laptop. Then when I have to pass emissions/safety inspections I just put my stock ecu back in and I can still monitor my a/f on the gauge that comes with the wideband kit.

The MTX-L wideband is a decent one, I know it is pretty popular in the DSM world or at least they use to be prior to me switching to Hondas.

 

It looks like it should do the job, but you'll still need to weld a bung into the exhaust somewhere to mount it.

 

Thanks guys, I appreciate your help!! So does my Honda.

 

Ill tell you this the 1st o2 sensor cant do it just put nos and a gauge in amd reads just strate 20.00 and dont go no where? On&

 

The downstream O2 just confirms the cat is functioning correctly. There is no point in having a wideband on stock tuning (stoich). The hx does have a special O2 maybe that is what you are thinking about, but that car is the high fuel mileage car.