2001 S60 Parking assist beeping continuously

[turtle8014]

I have a 2001 S60 with the standalone version of the parking assist module which takes its power from the taillights and has its own buzzer. My issue is that when I turn on the park assist using the red switch in the trunk and engage reverse the buzzer first lets out a short beep and after that beeps continuously for around 10s after which it stops beeping altogether. If I re-engage the reverse gear the same thing happens again.

Due to the standalone nature of the module my car does not have AEM which means that vida/dice cannot communicate with the park assist module which in turn means that I am unable to determine if there are any DTCs. I have tested that all four of the sensors make a clicking sound when the reverse is engaged so none of them seem to be outright broken. Can the module itself be broken in this way? I would like to know if there are any more diagnostics steps I could take (preferably ones that don't require taking off the entire rear bumper) before starting to scour parts from the junkyard.