12 63 520 Replacing main relay

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Switch off ignition.

Connect DIS Tester.

Release screws (1).

Fig 1: Releasing Screws

Courtesy of BMW OF NORTH AMERICA, INC.

Remove electronics box cover.

Installation:

Correctly install wiring harness with grommet in electronics box cover (water tightness).

Hook cover (3) into hinges of underside of electronics box (1). Then correctly install upper stop (2) above hinges on underside of electronics box.

Fig 2: Hooking Cover Into Hinges Of Underside Of Electronics Box

Courtesy of BMW OF NORTH AMERICA, INC.

Arrangement:

Main relay of Digital Motor Electronics
Engine fuses of Digital Motor Electronics

Fig 3: Identifying Main Relay Of Digital Motor Electronics

Courtesy of BMW OF NORTH AMERICA, INC.

Notes On Troubleshooting:

If the starter motor cranks the engine during the starting sequence but the engine fails to fire, then:

Check engine fuses.
If fuses are blown, replace them completely with fuse holder.
Find out why fuses have blown.

Continue troubleshooting as per DIS instructions.