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Home >> BMW >> 2001 >> Z8 >> Repair and Diagnosis >> Electrical >> Motors, Switches, Relays >> Bus System Troubleshooting - Overview - E36, E38, E39, E46, E52 & E53 >> Bus System Troubleshooting >> Motor Bus (M-Bus) >> M-Bus Troubleshooting >> Failure Of The Bus Ribbon

Failure Of The Bus Ribbon

The following faults can occur to the M-bus wiring:

The IHK control module checks the M-bus for continuous position feedback from the stepper motors. If the M-bus is interrupted then the control unit will store a fault for every stepper motor on the bus.

In order to determine if a stepper motor is at fault for the lack of communication, disconnect one stepper motor at a time while monitoring the M-bus signal line with a voltmeter or oscilloscope. The pattern or voltage should return to normal when the defective stepper is found. As a confirmation that communication is restored, change the setting on the IHK panel, if the remaining connected flap motors assume the selected position communication is OK.

Diagnosis of the M-bus is carried out by the DISplus/MoDiC via the IHK module. Available in the Diagnosis Program are: