Hi,
What is happening leads me to think the control module is failing and not powering the lamp. Is there a red wire at the lamp assembly? Have you checked it for power?
As far as the issue, it could be a few things. However, we would be guessing at this point. What really needs to be done is the can-bus needs scanned for diagnostic trouble codes. If there is an issue with the lamp control module, it will have codes stored in it.
According to the manual, for troubleshooting, you need to use Vehicle Diagnostic, Testing, and Information System (VAS 5051A) in the operating mode " Guided Fault Finding". That would walk you through diagnostics.
Now, most people don't have that type of equipment, but a scan tool designed for reading the CAN should work. CAN stands for controller area network. Basically, the different modules are tied together via a few wires. This type of scan can retrieve codes regardless of the module storing them.
Here is a link explaining how it's done:
https://www.2carpros.com/articles/can-scan-controller-area-network-easy
Let me know your thoughts.
Joe
Thursday, January 12th, 2023 AT 7:14 PM