ECU Pinouts

The ECU is the very heart of your engine management system. Almost everything under the bonnet, and a lot of the stuff inside the car, connects to it in some way.

When things start going wrong, it's essential to check that signals are getting to or coming from the ECU, and that means testing the wiring. To help you identify what goes where, here are the pinouts for each generation of E30 ECU.

Jetronic

Jetronic's primitive management system only controlled fuelling, so the ECU is little more than an injection control unit. The control model uses a 25-pin plug, with Pin 1 at the cable end.

Pin	Function	Pin	Function	Image
1		14

Motronic 1.0

The Motronic 1.0 ECU employs a 35-pin plug to connect to all the engine bay components.

Pin	Function	Pin	Function	Image
1	Ignition coil output	19	Ground
2	Idle switch	20	Main relay
3	WOT switch	21	Tachometer
4	Cranking signal	22	AFM Temp sensor
5	Ground/Crank PosS Gnd	23	Inlet Air Temp/Crank SpS Gnd
6	AFM ground	24	O2 sensor signal *
7	AFM signal	25	Crank position sensor 1
8	Crank speed sensor 1	26	Crank position sensor 2
9	AFM supply	27	Crank speed sensor 2
10	Auto only special	28	Water Pressure switch
11	Fuel consumption gauge	29	A/C switch (if installed)
12		30	+Inlet Air Temp
13	Water Temp	31
14	Injector output cyl 3&4	32
15	Injector output cyl 1&2	33	ICV pulse
16	Ground	34	ICV pulse
17	Ground	35	Injector ground
18

Motronic 1.1

Motronic 1.1 uses a much chunkier plug, fitting 55 pins into three rows. Unlike Jetronic and Motronic 1.0, pin 1 is now at the end furthest from the cable.

Pin	Function	Pin	Function	Pin	Function	Image
1	Timing Control - to coil and O2 sensor	20		38
2	Ground	21		39	Programming voltage - Diagnostic Plug
3	Fuel pump relay control	22	Idle speed control	40	A/C on input
4	Idle speed control	23	O2 sensor heater	41
5	Evaporative purge valve	24	Ground	42	Park/ neutral input (auto only)
6	Engine Speed output- to instrument cluster	25		43
7	AFM input - pin 2	26	AFM common- ground pin 4	44	AFM air inlet temp- pin 1
8	Cylinder ID sensor input	27	Start input- to ignition switch and coil	45	Coolant Temp input
9		28	O2 input	46
10	O2 sensor input	29		47	Engine speed input
11		30		48	Engine speed input
12	AFM reference output- pin 3	31	Cylinder ID sensor input	49
13	RXO - diagnostic plug	32	Fuel rate output- to instrument cluster	50
14	Ground	33		51
15	Check engine light - to cluster	34		52	Closed throttle input - pin 1
16	Injectors 1,3,5	35		53	WOT input - pin 3 Note: TPS pin 2 is ground
17	Injectors 2,4,6	36	Main relay	54
18	Power input main relay	37	Power input - to main relay	55	TXD - diagnostic plug
19	Ground