BYD ATTO 3 (e-Platform 3.0) U300317 EPB Battery Soft Overvoltage Fault

U300317 indicates a soft overvoltage condition detected by the electronic parking brake (EPB) system. The fault affects EPB electrical power management, where the controller monitors its supply voltage and detects when it rises above the expected operating range. The BYD ATTO 3 uses BYD’s e-Platform 3.0 architecture, with this generation introduced from 2022 and continuing onward.

Symptoms

• EPB warning light illuminated
• Electronic parking brake warning message
• EPB may fail to apply or release
• EPB operation may become intermittent
• Multiple voltage or communication-related faults may be stored
• EPB functions may become temporarily unavailable
• Warning may appear following a 12V system voltage event
• Vehicle may display additional electrical system warnings

Possible Causes

• Excessive 12V auxiliary system voltage
• Fault in the 12V charging or power-management system
• Incorrect auxiliary battery voltage
• Voltage regulation fault
• Electrical supply surge
• Poor or unstable EPB controller power connection
• Damaged or corroded battery terminals
• Wiring fault causing abnormal voltage at the EPB controller
• EPB controller internal voltage-monitoring fault
• Previous electrical system fault or incorrect jump-start procedure

Diagnosis

Diagnosis should begin by confirming U300317 and checking the 12V auxiliary system voltage under the operating conditions specified by the manufacturer. Battery voltage, charging-system operation, EPB controller power and ground circuits, and voltage stability should be evaluated against factory specifications.

Other stored voltage or network-related faults should also be reviewed to determine whether the EPB overvoltage condition is caused by a wider electrical supply problem. Accurate diagnosis is particularly important when parts availability and repair costs are considerations for New Zealand vehicle owners.

Accurately diagnosing this fault often requires manufacturer testing procedures, wiring diagrams, connector pinouts, specifications, and system calibration information. Access to the factory service manual significantly reduces diagnostic time and helps prevent unnecessary parts replacement.

Applicable Years

2022, 2023, 2024, 2025, 2026, onwards

To order the correct OEM Service and Repair Manual for your BYD ATTO 3, submit your request using the form below and our team will provide the ordering details.