Hi Mike!
The Signal function enables you to record specific vehicle behaviors. For instance, a signal is triggered if the oil temperature reaches a particular value. This signal can then trigger notification by email or SMS as an event. I think the tricky thing for you will be to find a signal that indicates the WS403 is powered down without having any power to the unit itself. You need a signal that to 100% indicates the unit is going to power down before the unit is powered down. Or for next time you get a WS503-BP that has an internal four amp-hour battery pack to keep essential systems functioning for up to a year after the loss of main system power.
In the User manual for Danfoss Telematics Solutions Portal on page 67 you can read about, first how to create a signal, and then how to use that in an event. For the signal there is a filter needed and that should be set to SPN Value.
I tried this out by following the manual and it works for me so if you have any more issues please don't hesitate to contact us again, either here or send some screen dumps to plus1helpdesk@danfoss.com!
Best regards
Nilla
PLUS+1 Helpdesk