(1) Erase the set DTC.
(2) Depress the brake pedal to change the power supply mode of the electric motor switch to ON (READY indicator: ON), then wait for 5 seconds or more.
(3) Check whether the DTC is set again.
Is the DTC set?
The trouble can be an intermittent malfunction. Refer to General Information - How to Use Troubleshooting/Inspection Service Points, How to Cope with Intermittent Malfunctions HOW TO COPE WITH INTERMITTENT MALFUNCTIONS.