O2 sensor heater...what can affect it?

[trackjunkie21]

I'm starting to think there may be something in the actual wiring from the computer to the relay, but I would try Nando's suggestion, seems like it may work.

[Beej '86 325es]

Have you swapped in a good working DME?

twice...and different chips.

I'm going to go ahead and do what nando suggested. Lately I've been replacing stuff just to replace stuff. The last thing I can do is rip out the whole wire harness and start from scratch...but sadly, I don't even think that would fix the problem.

The other day I saw a photo of an E34 M50 wire harness. I thought I had an 325 harness, but now I'm not sure. The reason I'm wondering is because the O2 portion of the harness is routed on the driver's side of the engine block. It's like I had to route it backwards to get it to the O2 sensor. I wonder if there's a difference there.

[328ijunkie]

+1 as I mentioned I've never had this issue....

[trackjunkie21]

Have you swapped in a good working DME?

[Beej '86 325es]

The ECU is supposed to control the O2 sensor relay from what i can see
If Pin 38 is not making its way to pin 85 of the relay then thats where your issue lies.
Power for the relay on both sides is provided by the Main/ECU relay.

Correct. I've checked continuity on every relay and sensor and all checks out. Something is telling the ECU to make a very clear "switch" between 8:45 and 9:00 after starting. Unfortunately I don't know (and doubt anyone on the forum does) what the innerworkings of the ECU logic. I'm sure other sensor(s) are involved though.

[328ijunkie]

The ECU is supposed to control the O2 sensor relay from what i can see
If Pin 38 is not making its way to pin 85 of the relay then thats where your issue lies.
Power for the relay on both sides is provided by the Main/ECU relay.

[nando]

because my ECU doesn't have an O2 activate pin - MS3. I think a lot of people are using the (terrible) Megasquirt relay board to power their widebands, or some other equally painful way. Why reinvent the wheel when BMW engineers have done all the work for me. :)

[Beej '86 325es]

That's not a bad idea! I've been researching time delay relays, but this is much simpler.

Out of curiousity, why do you have yours wired this way?

Thanks!

[nando]

I'm stumped!

a better idea would bet to run a jumper from pin 85 of the FP relay to pin 85 of the O2 relay. then the FP signal would turn on both (this is safe, I've had mine wired like this for ages). Of course remove the connection to pin 85 of the O2 relay from the ECU.

[Beej '86 325es]

Tested with C101 pin 6 disconnected from x20 pin 22. Same result. 8-9 minutes until it clicks on. Lost power to the diagnostic port.

Reconnected pin 6 and swapped DMEs. Same result. 8-9 minutes until it clicks on.

O.M.G. I have no idea what else to check.
It seems like it's got to be something not with wiring, but with the logic. Something is telling it to wait to click on.

Would there be any harm in installing a jumper in place of the relay? I guess I don't understand the purpose of it if it's always supposed to be on anyway.

[Beej '86 325es]

HD Video of relay clicking on after 8-9 minutes

So for some reason the relay isn't clicking on until about 8-9 minutes. I've tested this 3 times on cold and warm starts with the same result.

I got to play with iMovie a bit and make an HD video of the problem. :)

http://www.youtube.com/watch?v=WjvLuaXvGH0

[Beej '86 325es]

like this

http://www.r3vlimited.com/board/showthread.php?t=192533&highlight=backfeed

[lolcantturn]

I did it exactly per that thread explains. I bought a blade insert from Autozone for about $5. It didn't really seem to change anything on my car though. But then again my 02 heat relay isn't working properly anyway. I've got an '86 325e chassis.

When I disconnect the green/violet wire from the E36 harness and the E30 harness and connect a direct wire from the E36 green/violet to the fuse 11 my car doesn't start anymore..am i doing something wrong?

[nando]

8 minutes? yeah, something's wrong. it should turn on immediately.

[Beej '86 325es]

I did it exactly per that thread explains. I bought a blade insert from Autozone for about $5. It didn't really seem to change anything on my car though. But then again my 02 heat relay isn't working properly anyway. I've got an '86 325e chassis.