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 notice
The following technical information and tips for practical use have been set up by HELLA in order to offer professional support to automotive workshops in their daily work. The information available here on this website is only to be used by appropriately trained specialist staff.
The reprinting, distribution, reproduction, exploitation in any form and 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, figures and descriptions are for explanation and presentation of the document text and cannot be used as a basis for installation or design. All rights reserved.
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