This may possibly be caused by the control unit for trailer detection, which converts the vehicle's lighting system comfort CAN messages from the electrical system control unit into trailer lighting.
Diagnostic procedure:
- Read out event memory of the control unit for the trailer function.
- Check the correct functioning of the comfort CAN bus and trailer control unit's voltage supply.
- (The control unit is installed in the boot's wheel arch, on the left side).
- If the signals measured with the oscilloscope are ok, the malfunction must be caused by the defective control unit for trailer detection.
Note:
In the case of incorrect communication between the trailer detection control unit and the control unit for on-board voltage, the taillights are actuated as an emergency function.
Important safety note
Technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their day-to-day work. The information provided on this website is intended for use by suitably qualified personnel only.
Reprinting, distribution, reproduction, exploitation in any form or disclosure of the contents of this document, even in part, is prohibited without our express, written approval and indication of the source. The schematic illustrations, pictures and descriptions serve only for the purposes of explanation and representation of the instructions and cannot be used as a basis for installation or assembly work. All rights reserved.
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