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Home >> BMW >> 2003 >> M3 2D Convertible >> Repair and Diagnosis >> Engine Performance >> Ignition System >> Engine Electrical System - Repair >> Electronic Switching Or Control Unit >> 12 63 520 Replacing Main Relay

12 63 520 Replacing Main Relay

Switch off ignition.

Connect DIS Tester.

Release screws (1).

Remove electronics box cover.

Fig 1: Identifying Electronics Box Cover
G03118137Courtesy of BMW OF NORTH AMERICA, INC.

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: Locating Hinges Of Underside Of Electronics Box
G03118138Courtesy of BMW OF NORTH AMERICA, INC.

Arrangement:

  1. Main relay of Digital Motor Electronics.
  2. Engine fuses of Digital Motor Electronics.
Fig 3: Identifying Main Relay And Engine Fuses Of DME
G03118139Courtesy 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:

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

Continue troubleshooting as per DIS instructions.

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