Engine wiring harness

This is appliable to all fortwo 450s with petrol engines.

The engine uses a separate wiring harness to the rest of the car which links all engine sensors, actuators and the ignition system to the Engine Control Unit (ECU) and the car's main wiring harness. The ECU has two connection sockets: one for the engine wiring harness and a second which connects to the car's main wiring harness.

The wiring harness looks as follows. This particular version has been cleaned, repaired where necessary, wrapped in waterproof Tesa Tape and fitted to a 698cc fortwo 450. There are some differences between wiring harnesses, most notably between 599cc and 698cc models but early 599cc models (mk1-3) all had minor differences driven by the need to constantly lower emissions.

With the wiring harness removed, it may not be overly obvious what each connector plug in to. This will hopefullly provide a single source of information you may require when working on the engine harness. With the exception of the lambda sensor circuit on pre-2000 models, all wiring cores are single colour.

The 599cc models all had a separate engine fuse and relay box located beneath the carpet under the left seat. One connector from the engine harness (Connector 'M') plugged into this unit to supply a number of circuits. When this fuse box was removed as part of the intoduction of the SAM unit in 698cc models, an inline connector was provided above the subframe on the left side. This allowed the engine harness to connect directly into the main harness for the car. In both cases, the connector serves the following equipment:

599cc fortwos (with electrical centre under left seat):
PinToWire SizeWire Colour
1 Ignition Coil Packs 2.5 (or 3x 1.5) Green (or 3x White)
2 Fuel Injectors 1.5 Green
3 Airconditioning compressor 1.5 White
4 - - -
5 Starter motor (start signal) 2.5 Blue
6 Intercooler fan 1.5 Yellow
7 Lambda sensors, cycle valve, vacuum valve 1.5 White
698cc fortwos (with connector above subframe):
PinToWire SizeWire Colour
1 Airconditioning compressor 1.5 Blue
2 Ignition Coil Packs 1.5 Red
3 Fuel Injectors 1.5 Green
4 Starter motor (start signal) 2.5 Blue
5 Intercooler fan 1.5 Yellow
6 Lambda sensors, cycle valve, vacuum valves 1.5 White

The following image is a diagrammic of the engine wiring harness for a 698cc fortwo (click to enlarge) which shows at which point along the wiring harness various connectors are positioned:

As previously discussed, slight changes have been made to the wiring harness throughout the life of the fortwo 450. However, the ECU has generally remained the same. The following table details the pin arrangement of the engine harness connector.

ECU Connector PinWire SizeWire ColourFunctionDestination Connector PinVariants
1 2.5 Blue Gear Motor (motor) 6 All models
2 - - - - All models
3 2.5 Green Gear Motor (motor) 1 All models
4 1.5 Yellow Clutch Actuator (motor) 3 All models
5 1.5 Yellow Clutch Actuator (motor) 6 All models
6 0.75 Yellow Cylinder No.3 Ignition Coil 4 All models
7 - - - - All models
8 0.5 Yellow TDC (Crank Position) Sensor 2 All models
9 0.5 Yellow TDC (Crank Position) Sensor 1 All models
10 0.5 Black Knock Sensor 1 All models
11 0.5 Red Gearbox RPM Sensor 1 All models
12 - - - - All models
13 0.75 Yellow Oil pressure switch - All models
14 0.5 Yellow Gear Motor (position sensor) 3 All models
15 0.5 Yellow Gear Motor (position sensor) 5 All models
16 0.5 Yellow Coolant Temperature Sensor 2 All models
17 0.5 Yellow Inlet Air Temperature Sensor 2 All models
18 0.75 Yellow Turbo Lambda Sensor (sensor circuit) 4 All models
19 0.5 Yellow Gear Position Sensor 2 All models
20 0.75 Yellow Throttle (sensor circuit) 6 All models
21 - - - - All models
22 - - - - All models
23 0.5 Yellow Clutch Actuator (position sensor) 4 All models
24 0.5 Yellow Clutch Actuator (position sensor) 2 All models
25 0.75 Green Cylinder No.3 Ignition Coil 3 All models
26 - - - - All models
27 - - - - All models
28 - - - - All models
29 - - - - All models
30 0.5 White Gearbox RPM Sensor 2 All models
31 0.5 Black Gearbox RPM Sensor Screen All models
32 0.5 White Knock Sensor 2 All models
33 0.5 Green Gear Motor (sensor +ve feed) 2 All models
34 0.5 Green Gearbox Temperature Sensor 1 Only up to Sept 2000 on 599cc
35 0.5 Green Gearbox Temperature Sensor 2 Only up to Sept 2000 on 599cc
36 0.75 Green Exhaust Lambda Sensor (sensor circuit) 4 From September 2000 on 599cc and 698cc
37 0.5 Green Throttle (sensor circuit) 5 All models
38 0.75 Green Throttle (sensor circuit) 3 All models
39 0.5 Green MAP Sensor 3 All models
40 - - - - All models
41 0.75 Green Lateral accelaration sensor 2 599cc models only
42 0.75 Yellow Lateral accelaration sensor 1 599cc models only
43 0.5 Green Clutch Actuator (sensor -ve feed) 1 All models
44 0.75 White Cylinder No.2 Ignition Coil  3 All models
45 0.75 White Cylinder No.2 Ignition Coil 4 All models
46 - - - - All models
47 0.75 White Alternator trigger - From Sept 2000 on all 599cc and 698cc
48 0.5 White Vacuum Valve (on intake for cat pre-heater) 2 From September 2000 on 599cc and 698cc
49 - - - - All models
50 - - - - All models
51 0.5 White Gear Motor (sensor -ve feed) 4 All models
52 0.5 White Coolant Temperature Sensor 1 All models
53 0.5 White Inlet Air Temperature Sensor 1 All models
54 0.75 White Exhaust Lambda Sensor (sensor circuit) 3 From September 2000 on 599cc and 698cc
55 0.75 White (Yellow/Brown)* Turbo Lambda Sensor (sensor circuit) 3 All models
56 0.75 White Throttle (sensor cicuit) 2 All models
57 0.5 White MAP Sensor 2 All models
58 - - - - All models
59 - - - - All models
60 0.5 White Gear Position Sensor 3 All models
61 - - - - All models
62 - - - - All models
63 0.75 Blue Cylinder No.1 Ignition Coil 4 All models
64 0.75 Blue Cylinder No.1 Ignition Coil 3 All models
65 0.5 Blue Vacuum Valve (on inlet for cat-preheater air pump) 2 Only on 698cc models
66 0.75 Blue Exhaust Lambda Sensor (heater circuit) 2 From September 2000 on 599cc and 698cc
67 0.75 Blue (Brown/Pink)* Turbo Lambda Sensor (heater circuit) 2 All models
68 0.75 Blue Cycle Valve 2 All models
69 - - - - All models
70 0.75 Blue Fuel Injector No.3 2 All models
71 0.75 Red (Blue)* Fuel Injector No.2 2 All models
72 0.75 Blue Fuel Injector No.1 2 All models
73 0.75 Blue Throttle (actuator motor) 4 All models
74 0.75 Blue Throttle (actuator motor) 1 All models
75 0.5 Blue Clutch Actuator (sensor +ve feed) 5 All models
76 0.5 Blue MAP Sensor 1 All models
77 - - - - All models
78 - - - - All models
79 0.5 Blue Gear Position Sensor 1 All models
80 0.75 Blue Lateral Accelaration Sensor 3 599cc models only

 * up to September 2000

 

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