vtec4clyfury

I've looked through numerous forums on here and still cannot find what i need. Its fairly simple i think. I just need to know which wire on the ECM wiring harness or going to the ECM is the oxygen signal (+) wire. I have a '94 Accord EX Coupe.

Its a sunpro gauge like you can get at autozone or wal-mart and its not the fanciest but i just want a good idea of my air/fuel mix. I already have the power, ground, illumantion. all that is fine. i just want to know which wire. I don't want to run the wire to the oxygen sensor because that just seems more work than i really need to do. So if anyone knows what color of wire and where about on teh harness its located please let me know. I really don't want to have to jack the car up and crawl under and find it.

AcsRcool

First of all, you've left out some essential information. You haven't told us what operating voltage range the guage is designed to see. Put another way, your gauge might expect to see a 0 - 1 Volt swing dependent on what the actual air/fuel ratio is. There are two problems with this if that is the case.

The Air/Fuel ratio is typically determined by the oxygen content in your exhaust. It's done with the O2 sensor. You probably have one in your exhaust manifold and one in your catalytic converter. The manifold sensor is the one your ECU uses to calculate your fuel-injection pulse width so thats the one you'd take the reading from. The other is to monitor proper operation of the catalytic converter.

However, there are two or three problems you are likely to run into. The first is that the voltage swing across the O2 sensor may be 1 volt in magnitude but it may be offset by another DC voltage. For example, the swing may be 2.5-3.5 V. This isn't gonna work too well with your gauge without some electronic middemen (maybe a differential amplifier). Also, depending on the construction of the O2 sensor, the ECU may read a current value from the circuit and not a voltage across the sensor. While these two things are related, adding a gauge to the circuit will change the impedance of the system and the readings for the ECU will be corrupted (also potentially solved with some custom eletronics - high impedance amplifier, etc).

If you can get past these first two electronic problems, there is still one big one left. The O2 sensors in the 5th gen accords are not wide-band sensors. I.e. their voltage/A/F ratio curves describe a switch type behavior. They show one signal for rich and another for lean with no linear middle ground. Your A/F gauge is essentially useless with this in mind because the reading will just oscillate between rich and lean. It might hover on one for a bit if you coast or really get on the throttle. The point is that to make this work, you really need some more sophisticated sensors and eletronics. I know that wide-band O2 sensing kits used by race teams run from 500-10,000 dollars.

vtec4clyfury

I know how its supposed to read, and its a 0-1 volt swing. But your telling this thing is useless and that no other a/f gauge can be used in my accord unless i'm willing to pay an ungodly amount of cash? And i want to wire it from the manifold i guess to get a proper reading.

AcsRcool

Yeah, the manifold is the sensor you want to tap. I'd recommend a Helms manual to help you find the right wire. You'd hafta find out some specs on the sensor to see what the output swing is. However, if the signal thats important to the ECU is the current from the sensor, don't fuck with it unless you have someone there who knows exactly what will happen electrically.

I dunno if its useless or not. You need to do some serious research on the sensor and the normal operating ranges and what the ECU is meant to see when your car is on.

bonestock

i think white wire of the o2 sensor. sold mine a while ago. its really a useless guage unless your running one with a wideband o2 sensor. its more for show. i got one cuz at the time i was running nitrous and thought it'd come in handy but when i sprayed it would just go to full rich. the only time it has really done anything useful was when i messed up on the nitrous jets and it went full lean i shutdown immediately and looked on my nitrous jet and there wasnt one in there!

vtec4clyfury

does anybody know how to do this. A few people tell me its a white wire and now a few are telling me its a green wire. And i dont' think there is an oxygen sensor on the manifold. The only one that know of is under the body of the car before the cat. I still need help with this....

DA808TWITCH

I got a 94 Accord EX too and I have the same question! If you find out how to run the guage to the ECM, and what wire it is...let me know! Thanks

vtec4clyfury

trust me i'll let you know, i was talking to a guy who did it in his 94 on here but he stopped emailing me. He said that he did run it to his sensor because it works better or something i forget. It just seems a hell of a lot easier and less painless to just wire tap into a wire IN the car rather than drill a hole or find a hole to get one wire under a car.

bonestock

i checked and i had it spliced on the white wire on the o2 sensor on the collector before the cat

DA808TWITCH

I know that the signal wire for the Air/Fuel Ratio is white going into the cat. I don't want any chance for my wires to melt and that is why I want to run it straight fromt the ECU, but there is like 100 white wires going into that thing!