DTC U01BF-00: Can Communication System: Communication Error To Backup Power Supply Unit (PYUL)

U01BF: 00 (PCM (PYUL)) DETECTION CONDITION AND POSSIBLE CAUSE

System malfunction location	CAN communication system: Communication error to backup power supply unit
Detection condition	The PCM detects communication error with backup power supply unit.
Fail-safe	Inhibits auto door lock operation. (with auto door lock system) Displays/turns on shift system warning indication/warning light. Inhibits engine-stop by i-stop control.
Possible cause	Malfunction in wiring harness (including connector/terminal) between sub battery and backup power supply unit (See CIRCUIT INSPECTION .) (See CONNECTOR INSPECTION .) Malfunction in wiring harness (including connector/terminal) between backup power supply unit and PCM (See CIRCUIT INSPECTION .) (See CONNECTOR INSPECTION .) Backup power supply unit malfunction (Refer to [BACKUP POWER SUPPLY UNIT REMOVAL/INSTALLATION ] ). PCM malfunction (Refer to [PCM REMOVAL/INSTALLATION ] ).
Repeatability verification procedure	Clear the DTC recorded in the memory. (See CLEARING DTC .) Replicate the vehicle conditions at the time the DTC was detected using the following procedure. WARNING: Observe legal speed limits when driving the vehicle and perform the procedure in a location where safety can be assured. To prevent an accident, work with two people when the vehicle is being driven (one person drives vehicle, other person operates M-MDS). Try to reproduce the malfunction by driving the vehicle based on the values in the freeze frame data/snapshot data.
Courtesy of MAZDA MOTORS CORP.
1	Sub battery
2	Backup power supply unit
3	PCM