You can try disconnecting the battery for 30 minutes, then reconnecting it.

VDash can clone your CEM I think, but at a cost. There is a Facebook group called Volvo Vida Dice & VDash Owners and Advice Group Worldwide where you can probably get more advice.

This video shows CEM cloning using programming software, just to give you an idea of how to remove and replace it. But the cloning involved soldering directly to the PCB. I think it';s possible to back up your CEM and write it to a new module via VDash, but there are several people on the FB group who will know a lot more than me, some who can if necessary connect to your car remotely if you have the necessary equipment and software at your end, but see if they can suggest anything else first.

 

I've replaced the battery recently so I suppose i've tried disconnected the battery for more than 30 minutes.

Watching that video, it looks a little out of my depth.

 

just a thought, would using a canbus trailer relay do the trick? Assuming the bulb holder could be cut and rewired- take a 12v feed off the battery to the trailer module, ground it, take a feed from the working light, and theres your new 12v live to the bulb holder from the new module

 

Maybe easier to run a feed from the front position lamp on the opposite side to a make and break relay. Use the wire from the working lamp as a switching signal, and power the other lamp directly from the battery via an appropriate fused connection through the switched side of the relay. I'd use a diode protected relay to protect the position lamp circuit and CEM from voltage spikes during switching. You'd want to use the existing working lamp circuit as the trigger feed to the relay rather than the power source for the opposing bulb, to avoid triggering canbus bulb warnings.

 

I'm sure you have checked, but has the previous owner replaced any of the bulbs with the crappy LED ones that can mess up the bus?? Go back to stock!