2007 BMW Z4 2D Convertible, AutomaticFACTORY OEM SERVICE PROCEDURE

B+ Cable Monitoring

The E85 B+ Battery Cable is routed from trunk area along the underside of the car into the engine compartment. If the cable is damaged in an accident or while driving over an obstacle, the BST is activated, protecting the vehicle from further electrical problems.

Fig 1: Identifying B+ Cable Monitoring
G03397756Courtesy of BMW OF NORTH AMERICA, INC.

The battery cable monitoring occurs via the low impedance shield of the battery cable, the monitoring shield. The monitoring point in the trunk at the BST is connected to the SBSR and the other monitoring connection in the engine compartment is connected to the SBSL.

Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.

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