adding a stock secondary o2 sensor for a 1995 240sx

[progman]

Hi,

When I bought my car it did not have the secondary O2 sensor installed because of an after market exhaust setup. I want my car to pass emissions and I believe that this sensor missing is causing my check engine light to turn on.

Anyways, I don't have a place to screw the sensor in. I have some 18x1.5 pitch bungs but they are for the normal sized o2 sensors. Does anyone know what size the secondary one is? where I can buy a mild-steel bung in that size?

I had another idea but I'm pretty sure it won't work. I could use the normal sized bung and put a normal o2 sensor in as the secondary. I'm pretty sure this won't do what I want it to do. Anyone ever try this?

Thank you!

[finalgear]

well lets see your car is a 95 but the question is is it obd I or obd II if it is obd one then you don't have a secondary o2 sensor and something else is causing the check engine light to kick on what i would do is pull the code or codes off the ecu first to find the problem.

[progman]

I do have a plug for a secondary o2 sensor that is currently unplugged. I didn't just assume I should have two.

Does anyone know the size of the secondary o2 sensor? Will it screw into a standard bung like the other o2 sensor?

I'll pull codes today to see what I get.

[RaVaGe]

The 2nd o2 sensor thread size is 12mm but i dont remember the pitch i think it was .50.I just had to do the same thing to my s14.If the ecu gives code 33 it is the o2 sensor goodluck dude

[progman]

finalgear was right. I was jumping the gun on this. I checked the codes and 82 came out. That is the CKPS. It's about 43 dollars and is only there for misfire detection! I bet I need it for emissions anyways. I have no clue why I have the plug for the o2 sensor. maybe someone used the harness from a different 240sx when they were messing with this. If you have more than one code will they all come out or just one at a time? it repeats 82 over and over. I hope that's the only thing.

Thanks for the size of the secondary o2 sensor. Hopfully I won't have to buy one of those too.

[dan14sweeney]

Man Im going to have to disagree i have an obd1 95 and it has 2 O2 sensors

[progman]

After I replaced the ckps (code 82) now code 77 comes up (rear O2 sensor). I don't know why code 77 never came up before... I'm going to move on replacing this as well. I hope no more codes decide to show up. for the sake of documentation I'll post my results once the O2 sensor is replaced.

[Chaluska]

For Everyones information, all S14's had a rear O2 sensor.

Dont be confused.

Mine was removed, and has No noticible difference, other than a check engine light, which my bulb is no more, so it doesn't bother me anyways.

[numbnuts240]

also, not sure if it's all 95's or just the later ones (i think it's all of them, iirc) are both obd1 and obd2.