Hi everyone,
I’m having a problem with the Volvo On Call system. The instrument cluster constantly displays: "Volvo On Call Service." When scanning with VDASH, I noticed that the control unit shows up in red.
Here’s what has been done so far:

• Backup battery replaced
• Timer reset
• Swapped with another module (still shows up red in VDASH)
• Checked fuse 19 (5A) – it’s intact -
• Wiring looks fine
  Additionally, the following appears in VDASH:
  The following units are not responding or are not present in the vehicle:

PHM

Please check the wiring.

The specific error code for the PHM is: CEM-U019800

Additionally, the following codes are also present:

CCM-B1A6909 and IHU-B1D5513 recorded.

...which is why I currently suspect a potential "ground zero" issue.

Is there a specific spot on the Volvo XC70 P3 (Nov. 2015 model) with a sunroof that I should examine more closely? Somewhere a corroded ground point might be located? Or are there other possible causes?

Best regards