Electrified vehicle low-voltage (LV) bus voltage control

A method for controlling an electrified vehicle having a high-voltage traction battery coupled by a voltage converter to a low-voltage auxiliary battery, comprising, by a vehicle controller:

• controlling the voltage converter to provide an oscillating output voltage to the low-voltage auxiliary battery in response to receiving a start signal while a vehicle brake pedal is released;
• and
• generating a diagnostic signal in response to variation of current supplied to the low-voltage auxiliary battery being less than a first current variation threshold;
• controlling the voltage converter to provide an output voltage greater than a first voltage threshold in response to receiving the start signal while the vehicle brake pedal is depressed;
• and
• generating the diagnostic signal in response to the current supplied to the low-voltage auxiliary battery being less than a first current threshold when the output voltage is above the first voltage threshold.

A system comprising:

• a traction battery coupled to an electric machine that provides propulsive force to an electrified vehicle;
• an auxiliary battery;
• a voltage converter coupled to the traction battery and configured to convert traction battery voltage to auxiliary battery voltage;
• and
• a controller programmed to:
• control the voltage converter to provide a non-oscillating voltage above a first voltage threshold to the auxiliary battery in response to the vehicle start signal being received while the brake pedal position signal indicates a released brake pedal, and an oscillating voltage having a peak below the first voltage threshold based on a in response to the vehicle start signal being received while the brake pedal position signal indicates a depressed brake pedal;
• wherein the controller is further programmed to generate a diagnostic signal in response to current to the auxiliary battery being below a corresponding current threshold while the voltage converter provides the non-oscillating voltage.