O2 sensor question

[95 V6 J body]

I have a 3100 running on a 95 F-body computer. The F-body computer wants to see an O2 sensor for each bank, but the 3100 only has one sensor. Is there a way to get this signal to properly split to cover both inputs on the computer, or do I have to install another sensor?

I'm hoping I can get away with using one, because I don't feel like shelling out the extra cash for another one. I have enough things I still need to buy.

Anyone have a good solution to this?

[bszopi]

The second sensor is not for the other bank. There is a pre-cat sensor and a post-cat sensor. There is an O2 simulator you can buy to plug into the post-cat plug which will make the PCM think the sensor is actually there. Do a search and I'm sure you'll find more info on it.

[3400-95-Modified]

The second sensor is not for the other bank. There is a pre-cat sensor and a post-cat sensor. There is an O2 simulator you can buy to plug into the post-cat plug which will make the PCM think the sensor is actually there. Do a search and I'm sure you'll find more info on it.

Are you sure??

He is using a 95 F-body ecm... Not OBDII so I dont think thats a pre and post cat sensor setup... He may need the second.

[95 V6 J body]

The second sensor is not for the other bank. There is a pre-cat sensor and a post-cat sensor. There is an O2 simulator you can buy to plug into the post-cat plug which will make the PCM think the sensor is actually there. Do a search and I'm sure you'll find more info on it.

No, on the 95 F-body, they used a left and right bank, which on a FWD car translates into a front and rear. The FWD cars only have one at the collector. They didn't start using pre and post cat sensors until ODB II.

Also, I don't want a simulator, I want the computer to know if it's rich or lean as it is supposed to. It's actually a better setup to be able to see each bank separately, but obviously there is work to do to install the front unit, and I have to buy another sensor.

[3400-95-Modified]

I say grab a yard sensor for now, and weld a bung on the cross over tube... that is if you have a cross over...

if the sensor is bad, well then yeah you have to front the cash for a second one... its worth it in the end though.

[ForcedFirebird]

Yes, the fbody ECM has a sensor on each bank, they are located at the beginning of the y-pipe (just behind the manifolds). If you want to keep the SFI fuction of the ECM, you really should have one on each bank. If you don't have a lobe on the cam, the ECM will go into MPFI mode and it will batch fire. Since the o2 sensor is sending a voltage signal, you should be able to send the signal from the one sensor to both inputs on the ECM.

BTW: Why would you want to use OBD1.5? You would have been better off using an OBD1 or OBD2. OBD 1.5 isn't tunable.

[95 V6 J body]

I chose that computer because of it's compatibility with my vehicle (95 Cavalier). Hadn't realised that you can't tune it. HPT will not work on it? The engine has no mods at the moment anyway, so it's not a worry (yet). If/when I get around to building something, I'll have to switch to MS II.

Also, are you sure on being able to wire the two outputs together? The factory O2 sensor for that ECM was just a standard single wire, which means it's an impedence sensor, no voltage. I know that the heated O2 sensor (which my engine has) gets voltage, but that's just for the heating element, is it not? The other two are just ground and signal. It should just be an impedence output as the single wire, else they wouldn't be compatible.

[Superdave]

just pull the heat shield off the crossover pipe, drill a hole in it and weld in another o2 bung.. wire in 2nd sensor and enjoy!


95 is OBD1.5 and is not tuneable, In your application a 96 or 97 computer/harness from a V6 Grand Am would work perfect and is tuneable.

[95 V6 J body]

just pull the heat shield off the crossover pipe, drill a hole in it and weld in another o2 bung.. wire in 2nd sensor and enjoy!


95 is OBD1.5 and is not tuneable, In your application a 96 or 97 computer/harness from a V6 Grand Am would work perfect and is tuneable.

I'll keep the 96 electronics in mind for the future, but since I've already done this swap, I'm going to keep the electronics as they are for now. The reason I chose them is that I was able to get the computer and wiring harness fairly cheap, it was the same ODB system as my car, and it was already set up for a 5 speed tranny.

[ForcedFirebird]

impedence sensor, no voltage

Your o2 is a voltage based sensor (all of the single wires are the same). A stock narrow band sensor reads from .01 to 1v, and a wideband reads from .01 to 5v. Athree wire sensor is a heated unit, and a 4 or 5 wire is a heated wideband. All read voltage, and just like using a narrow band AFR guage, two signals can be taken off of one sensor (i would recommend a common ground between the two).

just pull the heat shield off the crossover pipe, drill a hole in it and weld in another o2 bung.. wire in 2nd sensor and enjoy!

I'm hoping I can get away with using one, because I don't feel like shelling out the extra cash for another one.

I thought the question was how to keep one sensor.

[95 V6 J body]

....I thought the question was how to keep one sensor.

The original question WAS how to do it with one sensor. I intend on puting in the second one eventually, but since I've got the 4 wire heated unit in the stock location right now, I don't want to just put a single wire unit in for the second, and I have plenty of other parts I need right now, so I don't exactly have the extra cash for another 4 wire O2 sensor. I'm looking for a way to use just one sensor for the time being.

I'm still confused about how a sensor that doesn't have any voltage coming to it puts out any voltage, but at this point it doesn't really matter, because for some reason, wiring both inputs to one sensor output isn't working. I tried wiring the output to both wires on the computer before my original post, and it ran like crap. Unhooked one wire, and it ran better. It didn't matter which one I unhook, but it doesn't like having them wired together.

I didn't realise that the 4 wire unit puts out a different value, either. That's probably part of my problem. Is the output higher with more O2, or less?

[ForcedFirebird]

Use a volt meter and see what you are getting from the signal wire , your ECM is looking for somewhwre between .01 and 1v.

[95 V6 J body]

Use a volt meter and see what you are getting from the signal wire , your ECM is looking for somewhwre between .01 and 1v.

Right, but if my sensor is putting out a higher value than 1v, is it telling my computer that it's too lean? I'm just wondering which way the scale goes. Does the output increase with more oxygen, or decrease?

[IsaacHayes]

A 97 3400 van ECM (or monte carlo/etc I too IIRC) is OBDII and can be tuned by DHP I know for a fact. The 97 is better than a 96 because it has more memory and more tables are opened up and you can tune more things.

[ForcedFirebird]

zero is lean