C101

The C101 plug is the biggest connector on the vehicle Loom. It allows the entire engine wiring to be disconnected from the rest of the vehicle, so that the engine can be removed easily. It is located on the bulkhead in the engine bay, next to the brake servo.

All of the wiring that passes through the C101 is a key part of the Engine Management.

There were two versions of the C101 plug fitted. The "round" style fitted to Motronic vehicles, and the "square" style fitted to Jetronic vehicles.

Motronic

Pin	Colour	Function	To	Image
1	Blue	Charge light	pin 16 blue plug inst cluster
2	Green/Yellow	Static oil level	Pin 16 check panel
3
4	Brown/Purple	Temp gauge	pin 26 blue plug inst cluster
5	Brown/Green	Oil Pressure light	pin 18 blue plug inst cluster
6	Green/White	Oxygen sensor relay	Fuse 9
7	Green	Switched power	Ignition switch
8	White/Black	Fuel rate input	pin 11 blue plug inst cluster
9	Black	Engine speed input	pin 7 blue plug inst cluster
10	Blue	Dynamic Oil level	pin 20 Check Panel
11	White/Green	Reset service lights	pin 22 blue plug inst cluster
12	Grey	Check Engine indicator	Check Light
13	Green/Purple	fuel pump relay	fuse 11
14	Black/White	Speed signal out to ECU	pin 10 white plug inst cluster
15	Black/Green	Unloader relay	pin 1 blue plug inst cluster
16	White/Black	Diagnostic connector	Diagnostic plug pin 6
17
18	Black/Yellow	Start	Ignition switch
19
20	Red/Yellow	ABS power	ABS control module

WARNING: There is one difference in the C101 design between the E30s, and that is Pin 20. On early vehicles, Pin 20 is a brown earth wire, while for some later vehicles Pin 20 is a live, unfused red/yellow wire for the ABS system. If you are changing your engine, CHECK PIN 20 ON BOTH SIDES OF THE C101 PLUG before connecting the battery.

If you have a brown wire connected, cut it away from the pin, and make sure the free end can't come into contact with anything. If it is red/yellow, then leave it alone. Of course, if the body side of your C101 has a red/yellow wire on pin 20, and your new engine loom has nothing connected to this pin, you need to add a wire, capable of carrying about 15A, from either of the terminals marked '87' on the DME relay socket to pin 20 of the the C101 plug, otherwise your ABS braking system won't work.

Jetronic

Pin	Colour	Function	To	Image
1	Blue	Charge light	pin 16 blue plug inst cluster
2	Green/Yellow	Static oil level	Pin 16 check panel
3
4	Brown	Temp gauge	pin 26 blue plug inst cluster
5
6	Green/White	Oxygen sensor relay	Fuse 9
7	Green/Purple	fuel pump relay	fuse 11
8	White/Black	Start	Ignition Switch
9
10		Live power from ignition	unfused
11
12
13
14
15	Black/Green	Unloader relay	pin 1 blue plug inst cluster
16	Brown/Green	Oil Pressure light	pin 18 blue plug inst cluster
17	White/Green	Reset service lights	pin 22 blue plug inst cluster
18
19