I have a similar issue with our MC 2012 titanium Ecoboost, but just limited to the forward collision alert. The warning lamp for the forward collision alert is on, and yet the adaptive cruise control works just fine - and they use the same sensor (I'm assuming - I can only see one likely candidate in the schematics called the Proximity Warning Radar Unit).
Like you, I have checked for diagnostic codes with an OBD tool.
I found this description in a manual for a 2014 Mondeo, and perhaps the same applies to our year:
"The CCM (Cruise Control Module) monitors the yaw rate signal from the
ABS module and compares it to the wheel speed and steering wheel angle signals. If the
ABS module determines the yaw rate is invalid, the CCM disables the adaptive cruise control. The message center displays the message COLLISION WARNING MALFUNCTION and/or ADAPTIVE CRUISE MALFUNCTION."
- so maybe it's something to do with the yaw rate ?