2015 V60 alarm problem

[GrahamHR]

Ongoing problem which I have mentioned on other threads. Everything pointed to the alarm siren, in particular the battery pack.

Well, I took the siren out. Opened the metal case using an angle grinder on the welds and on one of the retaining tabs, so it could be levered clear of the plastic. Levered that clear.

Managed to open it ( two halves tightly clipped together).

Battery looks fine, no leakage. Checked the voltage; 2.6V. The battery pack label indicates it is nominally 2.4V (550mAh) , so it looks like it is fully charged and the fault lies elsewhere.

I put my code reader on the car. I get these error codes, which cannot be erased.

B1D1787. Battery backed sounder. Bus signal/ message failure. Missing message

Fuel system/ combined system
U016700. Lost communication with vehicle immobilizer control module

Engine control module
U016700. Lost communication with vehicle immobilizer control module


Any ideas?