BMW M57 184/193 Bhp body loom fitting guide

Wiring Colours:
Red Wire: Ignition live from key switch. Connect via a 7.5a fuse.
Grey Wire: RPM Signal from ECU for tachometer.
Brown / Yellow Wire: Alternator warning light. This warning light is ground switched.
White / Brown wire: Oil Pressure warning light. This warning light is ground switched

Blue Wire:
Fuel pump relay activation wire.
This activation wire is ground switched.
See the footnotes at the end of page.

Ring Terminal:
Connect to a good solid ground.

ECU Connector:
Connects to the 4^th Socket from the right of the ECU.
Note: It will only fit in it’s proper place due to the connectors being different sizes.

Throttle Pedal Connector BMW:
Plugs into the throttle pedal.

Throttle Pedal Connector Transit:
Plugs into the throttle pedal.

Throttle Pedal Connector Defender:
Plugs into the throttle pedal.

OBD2 Connector:
Mount where you wish.

Main Power Relay and ECU Power Feeds.
It is assumed you will be using the blue main relay, the small main fuse box and the ECU power connector from the donor vehicle. This is a removable harness from the under bonnet ECU box. The Thick RED wire with the ring terminal on goes to the battery 12v ideally via a 100A fuse. The thick Brown/Orange wire connects to ground.
Please note you will need a wire with a minimum 6mm² diameter to cope with the current draw to the battery.

A brief explanation of ground switching.
Ground switching is when the electrical circuit is completed by switching the ground side of the of the circuit. In our case, the ECU switches the ground on and off on the warning lights and the fuel pump relay to activate and deactivate them. Please see the schematics below for an explanation.

Fuel Pump Relay:
It is anticipated that you will be switching the original fuel pump relay from the vehicle which will in 99.9% of cases be ground switched so check the wiring diagram.
In the event you do not have a fuel pump relay and need to install one, the schematic on the right will suffice.

Alternator and Oil Pressure:
The Alternator and the Oil Pressure warning lights have an internal voltage feed from the instrument cluster they are located in.
Wire up the loom as shown to the instrument cluster connector or in a suitable place in the original wiring loom going to the instrument cluster.