AU
P056300

DTC P056300 indicates the IPB (Intelligent Power Brake) ECU detects its 12V supply voltage exceeds the system-calibrated safety threshold (typically 16V-18V, depending on vehicle calibration) — Atto 8

Braking System

DTC P056300 indicates the IPB (Intelligent Power Brake) ECU detects its 12V supply voltage exceeds the system-calibrated safety threshold (typically 16V-18V, depending on vehicle calibration).

In BYD DM-i and other new energy vehicles, the IPB system integrates electro-hydraulic brake assist, ESC, ABS, and automatic emergency braking.

This fault means the IPB module detects an abnormally high input voltage, which can damage internal solenoid valve coils, motor drive circuits, or sensors.

As a result, the system stores the fault code and may enter a degraded protection mode, limiting or disabling ESC/ABS functions.

This causes a hard brake pedal and increased braking distance, severely compromising driving safety.

Distinguish this code from engine management system DTC P0563: DTC P056300 applies specifically to the IPB system.

Typical causes include abnormal DC-DC converter output, IPB internal voltage monitoring circuit faults, or poor circuit grounding.

5
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1DC-DC converter voltage regulation failure: On DM-i models, the DC-DC converter converts the high-voltage battery output to 12V low voltage. If the internal regulation circuit fails, the output voltage may exceed 15V or even rise above 16V, causing the IPB to report an overvoltage fault.
  • 2Internal fault in the IPB electro-hydraulic module: The voltage monitoring circuit (A/D converter) inside the IPB ECU drifts or fails, falsely reporting excessively high voltage while the actual measured external voltage is normal.
  • 3Abnormal contact resistance in the power supply circuit: Loose, oxidized, or poorly contacting IPB power wiring harness connectors (such as plugs A03 and B02), or corroded or insufficiently torqued ground points (G101, G102, etc.) cause the reference ground potential to drift and the ECU to detect a relative voltage increase.
  • 412V battery internal resistance too high: Battery aging or sulfation increases internal resistance, causing terminal voltage to rise rapidly during charging and exceed the IPB monitoring threshold.
  • 5Charging and distribution assembly fault: On some models, a faulty DC-DC control unit inside the charging and distribution assembly causes the output voltage to rise uncontrollably.
What To Do
  • 1
    Read freeze frame data: Use the VDS2000 or Launch X-431 diagnostic tool to read the DTC freeze frame. Record the specific voltage value (Voltage_Battery_Value), vehicle speed, time, and system status when the fault occurred to determine whether the fault is continuous or intermittent.
  • 2
    Measure high and low-voltage system voltages: With the vehicle in the Ready state, measure the voltage across the battery positive and negative terminals using a multimeter (normal: 13.5-14.5 V). Simultaneously read the actual IPB supply voltage (IPB_Voltage) in the VDS data stream. Compare the two values to check for circuit voltage drop or monitoring errors.
  • 3
    Check DC-DC output characteristics: Connect an oscilloscope to monitor the DC-DC output waveform and check for voltage spikes or excessive ripple. If the DC-DC output continuously exceeds 15.5V, check the charging and power distribution assembly or the DC-DC converter. Perform a swap test if necessary.
  • 4
    Inspect the IPB power supply circuit: disconnect the IPB wiring harness connector; check terminals A03 (constant power), A04 (ignition power), and other terminals for oxidation or backed-out pins; measure the voltage drop of the power supply circuit from the battery to the IPB (should be less than 0.2V); check the tightness of the IPB housing ground point and the battery negative ground point (standard torque is usually 8-10N·m); sand any corroded ground points.
  • 5
    IPB system self-check and calibration: After repairing the power supply, clear the fault codes, bleed the IPB system, calibrate the sensors (steering angle sensor and pressure sensor), and perform a function test. If the fault persists and the measured voltage is normal, replace the IPB electro-hydraulic brake assembly.
Real-World Cases
BYD DTC AI Analysis

Song PLUS DM-i charging and power distribution assembly fault caused the braking system to log P056300

✓
A 2021 Song Plus DM-i with 23,000 km displayed "Brake System Fault" and "ABS Fault" warnings. VDS read DTC P056300 (System Voltage Too High) and multiple IPB communication faults. Voltage at the DC output terminal fluctuated between 13.8 V and 16.2 V, well outside the normal range. The DC output wiring, ground connections, and fuses showed no abnormalities. Replacing the charging/distribution assembly stabilized voltage at 14.2 V, cleared the fault codes, and restored the brake system to normal. The cause was an internal DC-DC control circuit failure in the charging/distribution assembly, which caused loss of output voltage regulation.
Original source ↗
BYD DTC AI Analysis

BYD E5: IPB Power Supply Circuit Poor Contact Causing Voltage Anomaly

✓
Dashboard ESC warning light on. Retrieved DTC P056300. Battery voltage measured 12.4V (normal). Inspecting the IPB wiring harness connector revealed oxidised and burnt terminals inside the A03 power plug, causing high contact resistance. During vehicle operation, poor contact generated voltage fluctuations and the IPB ECU detected transient overvoltage. Sanded earth point G101, replaced the IPB power harness connector, retightened the battery negative earth bolt, cleared the fault codes. Fault resolved.
Original source ↗
BYD DTC AI Analysis

Tang DM-i DC-DC output fault caused overvoltage warnings in multiple systems

✓
The charging gun tripped during DC fast charging. The dashboard displayed "Low Voltage Power Supply System Fault" and "Braking System Fault". VDS scan revealed P056300 and voltage-related faults in IPB, ESP, EPS, and other systems. Live data from the low-voltage battery manager showed system voltage at 16.8V, with charge/discharge status flickering between "Charging" and "Discharging". DC-DC output voltage measured above 16.5V. Diagnosed as faulty DC-DC regulator inside the charging and power distribution assembly. Replaced the charging and power distribution assembly. System voltage restored to 14.1V, all system fault codes cleared, and normal fast charging operation restored.
Original source ↗
BYD DTC AI Analysis

Song Pro DM-i IPB Internal Voltage Monitoring Circuit Fault

✓
No accident history. The "Check Brake System" warning appeared intermittently during normal driving. VDS showed intermittent fault code P056300. Freeze frame data indicated 17.1V when the fault occurred, but real-time measurements showed both the battery and DC-DC output at a normal 14.0V. Inspected the IPB power supply wiring, ground points, and harness connectors—no faults found. Diagnosis: drift or damage to the IPB ECU internal voltage sampling circuit (A/D converter), causing false high-voltage warnings. Replaced the IPB electro-hydraulic brake assembly (part number SC-EE-3610100). Monitored continuously for one week; the fault has not returned.
BYD DTC AI Analysis

Qin PLUS DM-i 12V battery aging caused charging overvoltage

✓
Vehicle: 3 years old, 50,000 km. Dashboard displayed braking system fault. Scan found active DTC P056300. Battery voltage measured at 15.8V immediately after startup. IPB data stream showed voltage rising simultaneously. DC-DC converter tested normal. Battery internal resistance measured 18mΩ (normal <8mΩ). Determined aged battery with high internal resistance forced DC-DC to raise output voltage to maintain charging current, triggering IPB overvoltage protection. Replaced 12V iron battery (model L2-400). System voltage returned to normal 13.8V; fault cleared.
Other Atto 8 Fault Codes
B110811This DTC indicates a short circuit in the air conditioning system PM2.5 air quality sensor (rapid detector). Specifically, abnormal continuity exists between the sensor power supply circuit or signal output circuit and body ground or battery positive. This causes the control module (ACU/air conditioning controller) to detect abnormal current or a voltage signal outside the valid range (typically 0V or supply voltage). The PM2.5 sensor monitors internal and external particulate concentrations, providing the data the automatic air conditioning system uses to switch between fresh air and recirculation modes. A short circuit disables the air quality monitoring function. This fault may force the air conditioning system into recirculation protection mode and trigger related thermal management system faults, as the air conditioning system acts as a key actuator in vehicle thermal management. In severe cases, the short circuit current can damage the internal sampling circuit of the air conditioning controller or overheat the wiring harness.B1109DTC B1109 indicates an open circuit in the communication line between the air conditioning system PM2.5 air quality sensor (dust concentration sensor) and the air conditioning control unit (AC ECU), or an open circuit within the sensor internal circuitry. Typically located in the air conditioning intake duct, this sensor monitors real-time PM2.5 particle concentration inside and outside the vehicle. It provides data to the automatic air conditioning system for intelligent switching between fresh air and recirculation modes and for controlling the air purification device. During an open circuit fault, the AC ECU cannot receive the air quality signal, triggering the system fail-safe mode. Symptoms typically include failure of the automatic recirculation function, abnormal air purification indicator light operation, or abnormal air quality data displayed on the air conditioning panel. Severe cases may compromise the cabin environment control strategy, but do not directly affect vehicle driving safety.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 overview →
Data confidence: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.