BMW M57 184/193 Bhp ECU Main Relay and Power Loom D.I.Y. Build

BMW M57 306D1 ECU Main Relay and Power Loom D.I.Y. Build
Some of the looms we supply do not have the main relay and power feeds to the ECU. This is because the donor vehicle has this in a handy unit in the form of the ECU connector and the blue main relay in the ECU box with the wiring to and from both parts that is easily removed from the car.
Some however may not have this unit. The drawings below are a wiring guide to create your own main relay loom using either a standard 30A vehicle relay or using the blue BMW main relay.
Please be mindful of your wire diameters as the ECU can draw a fairly high current whilst running.
From the battery, via the fuse to the main relay terminal 30 you require a 6mm² wire.
From the main relay terminal 87 to the joint where the wires are split into two to feed the ECU, you require a 6mm² wire.
From the joint wires are split into two to the ECU connector you need two 2.5mm² wires, one to pin 1 and one to pin 8 on the ECU power connector.
On the ground side, each ground pin (Pins 4, 5, and 6) requires a 2.5mm² wire to ground.
The brown wire which activates the relay is low current and a 0.5mm² diameter wire can be used.
If using a standard relay the red wire between terminal 30 and terminal 85 on the relay is low current and 0.5mm² diameter wire can be used. If using the blue BMW Main relay, this connection is internal to the main relay and not required.