c101 and x20 wire diagram (e30 M50 adapter)

[brianao34]

Bump for the best wiring thread I've seen yet. Definitely worth a read

[nando]

hook up the X20 brown violet to the C101 brown violet. Ignore brown/yellow. that's all you need to do..

[Mr.SWISS]

the cluster doesn't use the brown/yellow wire. that's an E36 cluster. the ground goes through the sensor itself into the block. trust me. you can hook that yellow wire up to a random pin on the C101, but it's not going to do anything. also, sometimes pin 20 is actually +12v, not a ground. that would be bad.

So I need to tap the single m20 sensor wire to the BR/VI wire on the coolant sensor pigtail?

[nando]

the cluster doesn't use the brown/yellow wire. that's an E36 cluster. the ground goes through the sensor itself into the block. trust me. you can hook that yellow wire up to a random pin on the C101, but it's not going to do anything. also, sometimes pin 20 is actually +12v, not a ground. that would be bad.

[Mr.SWISS]

you don't need the brown/yellow wire either. the E30 sender/cluster only uses 1 wire. there's no pin to connect the brown/yellow to.

Well, I had to tap one of the 4 wires from the sensor pigtail. I had my head rebuilt with an OBD1 head so I had the provision for the e30 and the OBD2 sensor. Of the 4 wires there are two for cluster temp and two for dme temp signal. It seemed to me the cluster used one of these for ground instead of grounding to the block like the e30 sensor, I left connected in case the circuit didn't ground to the engine. I ran my single wire off the M20 sender to the BR/YW wire that is running to pin 11.... I think it ends there.

Few things i see. Recheck where C101 Pin 7, 12, 14, and 20 go. You have them going to the wrong places on the X20.
Hint: 2 of the wires arent on the X20 theyre on another connector
;)

14 is going to 9, just got that sorted. Throw a brotha a bone on 12 cmon!



IIRC the M52 and S52 harness and DME are the same please correct me if they are different.

[nando]

you don't need the brown/yellow wire either. the E30 sender/cluster only uses 1 wire. there's no pin to connect the brown/yellow to.

[328ijunkie]

Few things i see. Recheck where C101 Pin 7, 12, 14, and 20 go. You have them going to the wrong places on the X20.
Hint: 2 of the wires arent on the X20 theyre on another connector
;)

[Mr.SWISS]

Anybody willing to lend a second set of eyes to look over this real quick. The OBD2 isn't as well documented trying to change that. Pins/wires are varying slightly from pre 95 e36's.

[nando]

brown violet

O2s have their own power, yes

interesting fact: late M20 harnesses have both brown/violet and brown/yellow connected to the coolant temp sensor (cluster), but the brown/yellow wire doesn't go anywhere..

[Mr.SWISS]

On OBD2 temp sensor pigtail which one goes to the cluster on the X20?

Is it the brown violet or the brown yellow? Trying to figure out which goes to the E30 single wire pigtail I have on the E30 sender. And do the O2's get power within the harness? Trying to make sure I covered all my bases this OBD2 is the same for the most part just a few loose ends lol.

[nando]

that it does, so by connecting it to X20 #22 you're really just powering the diagnostics port (which I don't care about), not the O2 relay which I think is where the confusion is coming from.

[FredK]

I'm pretty sure that x20 pin 22 passes switched power to the diagnostic connector (X6002 pin 16), and if it's not connected, a code reader won't work. I think I thought the same thing at one time and did not make the C101-6 to x20-22 connection.

But yeah, you're right, C101 pin 6 is just a switched hot and can be used to power the ABS, among other things.

[nando]

I've read this entire thread and done my own research, this is what I've come up with:

http://www.megasquirt.325ix.com/MS_to_Motronic/C101%20to%20X20.html

What gets really confusing is what people are doing with C101 #6 (O2 relay on the E30) and C101 #20 (ABS relay, powered from some random place, apparently).

If I'm not mistaken, the E36 harness powers the O2 relay directly from the main relay, and has no connection to the X20 at all. The E30 harness powers the O2 relay by connecting C101 #6 to fuse 9.

So what then, is the purpose of connecting C101 #6 to anything? I've seen a few suggest X20 #22, which goes to the E36 fuse box (fuse 25 or something), which doesn't exist on the E30, making it a dead end. As far as I'm concerned, there's no requirement to connect C101 #6 to anything on the E36 harness side.

Then we get to the late model ABS relay, where there is just as much confusion. It just needs switched power, and not a whole lot - the pump itself is connected directly to the battery.

I think the simplest way is to connect C101 #6 to C101 #20. That will power the ABS relay through fuse #9. If you look at the E30 harness, it basically does the same thing, only it doesn't go through fuse #9. I think the power requirements for tripping a relay are small enough that the 15a fuse at #9 should be enough.

Does any of this make sense? It's sort of unbeleivable that 10 years into swapping M50s and there's nothing concise about the C101/X20. I know there are harness differences on E30s but they're not that significant. There's more bad information on the web than useful.

[Frog]

Can't find anything for early 318i. ugh!

[jogfrogjog]

anyone have a pic of the back of the cluster or the pin out for the green connector?