Engine Loom E36 m42 to E30 m40

[MarcoPratas]

Hi! I've an E30 M40B16 with E36 M42B18. The engine swap it's ok BUT my problem is with the engine loom because the M42 loom is X20 plug and I can't found a diagram to adapt my c101 to the X20. Can you help me? THX

[agent]

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[jaredmac11]

I was once putting an E36 M42 & loom in to my E21; decided to mutate the M42 a bit and use the E30. Here is what I found. It may be useful to you. Of course everything below is highly simplified since the E21 is a simpler machine. But its a start to key components.

E36 X20 pin # \ Color \ Purpose
23 \ Brown/Grey \ Oil Pressure Switch
13 \ Green/violent \ Fuel Pump Power
25 \ Blue \ Alternator Exciter
6 \ ??? \ Switched Power to O2 sensor heater
21 \ Green \ ECU Power
15 \ Black/Green \ Starter Signal
12 \ Brown/Violet \ Coolant Temperature (Gauge)
20 \ Black/Green \ Tachometer

[bmwman91]

Good info. Question about the E36 loom...does it actually reach into the glove compartment where the ECU is in the E30? The E36 ECU is under the hood.

[jaredmac11]

Good info. Question about the E36 loom...does it actually reach into the glove compartment where the ECU is in the E30? The E36 ECU is under the hood.

The E36 loom actually appears to be longer. However, I cannot comment the distance between the penultimate connector and the ECU. Dunno if that makes sense.

I have em both hanging in my garage and can find out if someone really needs to know ; )

[bmwman91]

Yeah if you could take a photo of the two spread out side-by-side with the 88 pin plugs sitting at the same point as references, that would be helpful. I am actually planning to convert to an M1.7.3 ECU from a Euro M43, and it might be the case that I want to run an E36 harness with it.

[jaredmac11]

Here's the pic. Honestly its difficult to discern if it will be too long or too short.

[bmwman91]

Cool, thanks. Yeah, there's no way the E36 harness is working in an E30 without crazy modifications, at which point it would probably make more sense just to modify the E30 harness.

What is the second big connector plug in the E36 harness for, next to the ECU connector? ABS unit?

[jaredmac11]

Cool, thanks. Yeah, there's no way the E36 harness is working in an E30 without crazy modifications, at which point it would probably make more sense just to modify the E30 harness.

What is the second big connector plug in the E36 harness for, next to the ECU connector? ABS unit?

Auto trans ECU/EGS

The M42 was off an auto, but I was using the getrag 240 anyways so it didnt matter. and I was planning on doing LOTS of chopping but decided to just use the E30 wiring harness and DME