Power Supply: Notes

Fig 1: Identifying MS45 Power Supply

Courtesy of BMW OF NORTH AMERICA, INC.

KL30 - Battery Voltage  : B + is the main supply of operating voltage to the ECM.

Power Supplies  : The power supplies (KL15 and ECM Relay) are fused to the MS45 ECM. The fuses are housed in the Engine Fuse Block located in the Electronics Box.

KL15 - Ignition Switch  : When the ignition is switched "on" the ECM is informed that the engine is about to be started. KL15 (fused) supplies voltage to the Engine Control Module Relay and the Fuel Injector Relay. Switching KL15 "off" removes the ECM operating voltage.

Fig 2: Ignition Switch Schematic

Courtesy of BMW OF NORTH AMERICA, INC.

Engine Control Module Relay  : The ECM Relay provides the operating voltage for

Ground  : Multiple ground paths are necessary to complete current flow through the ECM.