Oxygen Sensor Wiring

[tonytony]

yes the main relay does get power and it clicks on, and i did ground out the brown/green wire just to get it running. I just wish there was a better way to do this. I just stuck a wire into the brown/green wire for the fuel pump relay and grounded it to the chassis and it click on. Then i soldered it to one of the wiring harness ground wires.

I'll have to try that test you performed on the o2 maybe mine is actually working.

[permit]

Do all of you have mismatching wiring harnesses/computers? I know mine are from different cars (e34 harness, e36 computer), and we were wondering if it might have something to do with it.

[tonytony]

NOPe not me..... at least i dont think so. I got everything as a deal from this guy; harness, dme, engine

[Rev Engineer]

yes the main relay does get power and it clicks on, and i did ground out the brown/green wire just to get it running. I just wish there was a better way to do this. I just stuck a wire into the brown/green wire for the fuel pump relay and grounded it to the chassis and it click on. Then i soldered it to one of the wiring harness ground wires.

I'll have to try that test you performed on the o2 maybe mine is actually working.

I think you need to verify the wire connection from the relay back to the dme. I'm guessing that the wire is bad, or maybe the dme is bad. Not sure what else it could be if everything seems to be ok other than the relay not turning on.

[Rocla]

After a lot of research, I still believe that the fuelpump relay and 02 heater relay problems are cause by 1 missing pin or wire on harness adapter or what ever you are running between e30 and engine harness.

I suggest that one wire is missing from e30 harness, so one wire on engine harness must be hooked to "somewhere" to get those relays(=dme ground feed to realys) work.

So please tell which wire of your engine harness plug aren't connected anywhere.

EDIT: and if someone has link to good and complete m50/s50/s52 diagram please post.

[tonytony]

i'll get the pins tomorrow, as it's late night over here in the states

[Mike B.]

I did the check on the relay like Rev Engineer and I get 12v after the car is warmed up. I still don't think it is working properly though, as the heater should start as soon as the car starts. That is the whole point of the O2 sensor heater.

I am going to try Jason's wiring fix to see if it makes a difference at startup. I will report back with my results.

[tjhartge]

I did the check on the relay like Rev Engineer and I get 12v after the car is warmed up. I still don't think it is working properly though, as the heater should start as soon as the car starts. That is the whole point of the O2 sensor heater.

I am going to try Jason's wiring fix to see if it makes a difference at startup. I will report back with my results.

should be the other way around
on when cold, and off when hot......

i read somewhere that the DME reads the O2 sensor only after a specific time, or does it only read after the heater has switched off

would it make more sense if the DME has a default program when the engine is cold, then reading the O2 after it is heated up?

[Mike B.]

The DME should run the heater based on engine coolant temp and MAF signal (load). During low loads or low coolant temps the heater is turned on so the sensor functions properly. This may be why I saw 12v when the engine was idling (low load ---> lower exhaust temp) after running for approx. 20 minutes.

The sensor provides a voltage to the DME depending on the which side of 14.7 A/F(stoich) that the exhaust gas falls and the DME should be constantly using this data and making adjustments.

If the heater is working properly, the sensor should be a full operating temp in 20 to 30 seconds. I assume the DME runs in open loop until the sensor has reached operating temps. I guess this could be considered the default program when the engine is cold. As I said earlier, I would expect the heater to start as soon as the engine is started and right now that is definitely not the case.

[Rocla]

What does the green/yellow wire from car harness to engine harness do?

AKG wiring table says it's for o2 heater and fuelpump relay, does it have swicthed +12 and where does i go?

On my friend non cat euro m20b20 harness that wire on goes to diagnostic socket...

[Mike B.]

Don't use the AKG wiring diagram - it's crap!

If you need some info, please PM me with your email address. I can send you the ETM .pdf files for 318's. Of course they may not account for Euro differences, but they should get you in the ballpark.

[1990m3]

why is AKG crap? he's been doing swaps since 1996, that's a lot of swaps. He probably knows what he's talking about.

[Mike B.]

I know Andreas and we do business with him quite a bit. He is a great guy and really knows his stuff. However, have you looked at the diagram online? It leaves alot to be desired. It may get you pointed in the right direction, but people always seem to end up here to finish things up. Completing swaps and presenting information on how to complete a swap are two very separate things.

I say take the time to look at the ETM for the respective years (chassis/engine), trace the wiring, and put together the diagram yourself. When you get stuck, come to R3V for answers.

[Rev Engineer]

I recall seeing some definate errors on the AKG pinout. But, it does help one get started. For my swap, I went through every wire/pin and determined it's function and direction of the current/signal. I've posted my findings here:

http://www.cityofdust.com/s50/e30%20s50%20wiring.xls

The green/yellow wire is power from fuse #9 that is intended to go to the o2 heater - maybe to the fuel pump relay too. The big difference with the e36 harness is that battery voltage goes directly to it.

I'm not convinced that my o2 heater is not working correctly. I think it might be working fine. My engine runs great and shows no codes. I'll know where my fuel milage ends up after this next tank since I've swapped in a 3.46 now. I'd like to see someone with a e36 confirm what happens to an unmodified car. I could check my 98 e36, but I don't think it would help since it's obd ii.

[1990m3]

I know Andreas and we do business with him quite a bit. He is a great guy and really knows his stuff. However, have you looked at the diagram online? It leaves alot to be desired. It may get you pointed in the right direction, but people always seem to end up here to finish things up. Completing swaps and presenting information on how to complete a swap are two very separate things.

I say take the time to look at the ETM for the respective years (chassis/engine), trace the wiring, and put together the diagram yourself. When you get stuck, come to R3V for answers.

Fair enough. I work with him sometimes too, as a matter of fact, i was at his shop yesterday. He only puts that online so people stop calling him for the answers. As you probably know, he just wants to do his work and not be bothered :) I'm with you Mike, I came to r3v for some answers for my swap too, it's a great resource!

Tell you what, using AKG's diagram my wiring has been the most reliable part of my swap, not one problem!