DTC U0001: High Speed CAN Communications Bus: Description
WARNING: This page is about a different car, the 2013 Ford Mustang. However, it is still accessible from the selected car via links, so may be relevant.
The PSCM monitors the HS-CAN bus when the ignition has been on for more than 5 seconds, when the voltage to the PSCM is greater than 6.5 volts and when there are no DTCs present that are inhibiting PSCM operation.
DTC U0001:88 (High Speed CAN Communication Bus: Bus Off) - This DTC will set if the PSCM detects that transmission of HS-CAN bus messages is not acknowledged by other modules for 400 milliseconds or if the HS-CAN bus is deemed to have a communication error for greater than 5 seconds.