AU
P056024

DTC P056024 indicates the IPB (Integrated Power Brake) detects a switch or attempted switch to the UBVR (Unified Backup Voltage Regulator) power supply mode — Atto 8

Braking System

DTC P056024 indicates the IPB (Integrated Power Brake) detects a switch or attempted switch to the UBVR (Unified Backup Voltage Regulator) power supply mode.

In the BYD IPB system, the UBVR is the internal backup power management unit.

When the main power supply (typically constant 12V power) experiences a voltage drop, instability, or failure, the system triggers a redundant power supply mechanism to maintain critical braking functions.

This DTC indicates: 1) abnormal main power supply voltage causing an automatic system switch; 2) a fault in the UBVR switching circuit; 3) an internal power management logic error within the IPB module.

This fault may affect functions including ABS, ESC, and Automatic Emergency Braking, risking degraded braking performance.

5
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Aging or undercharged low-voltage battery (12V battery) causes a sudden voltage drop during startup or driving, triggering backup mode.
  • 2Poor contact, loose connection, or corrosion in the IPB module power supply circuit, causing intermittent interruption of the supply voltage.
  • 3DC-DC converter fault (DM-i models) causes unstable high-voltage to low-voltage output, failing to meet IPB operating voltage requirements.
  • 4Fault in the IPB electro-hydraulic module internal power management circuit or UBVR changeover relay, causing false reporting or failure to switch back to the main power supply.
  • 5Prolonged vehicle parking or frequent short-distance driving prevents the battery from fully charging, resulting in critical system voltage.
What To Do
  • 1
    Use the VDS2000/3000 diagnostic tool to read the complete fault code stream, confirm whether P056024 is a current or history fault, and check the system voltage in the freeze frame data.
  • 2
    Measure the low-voltage battery static voltage (should be ≥12.4V) and dynamic voltage during startup/driving (should stabilize at 13.5-14.5V). Check the battery state of health (SOH). Charge or replace the battery if necessary.
  • 3
    Check the IPB module power fuse (usually F1/18 or F2/17, depending on vehicle configuration), power wire (B+), and ground wire (GND) for secure connections. Measure the voltage drop; it must be <0.1V.
  • 4
    Disconnect the IPB module connector. Check the terminals for push-out, oxidation, or water ingress. Measure the voltage stability at the power supply terminal. For DM-i models, also check the DC-DC output voltage.
  • 5
    If wiring is normal but the fault is intermittent, update the IPB module software to the latest version. If the update fails or the fault persists, replace the IPB integrated electro-hydraulic brake assembly, and perform brake bleeding, calibration, and ESC yaw sensor learning.
Real-World Cases
BYD DTC AI Analysis

Aging 12V battery in Song PLUS DM-i intermittently triggers P056024

✓
After sitting parked for 3 days, the vehicle started with ABS/ESC warning lights on. Scanned DTC P056024 (current). Static battery voltage measured only 11.8V; load test showed excessive internal resistance. Replaced the OEM 12V battery (60Ah AGM), cleared the DTC, and followed up for one month with no recurrence. Analysis: The aged battery caused cold-cranking voltage to drop below 10V, triggering the IPB to enter UBVR mode for protection.
BYD DTC AI Analysis

Internal power chip failure in IPB module causing persistent DTCs

✓
The brake system warning light illuminated suddenly while driving. P056024 was present and could not be cleared. Battery voltage measured normal at 14.2V; IPB power supply harness showed no abnormalities. Disassembled the IPB module and found the MOSFET in the UBVR switching circuit on the internal PCB burnt out. Replaced the IPB assembly to resolve the fault. Old part analysis revealed batch components had insufficient voltage rating.
BYD DTC AI Analysis

Water ingress into the wiring harness connector caused oxidation and poor contact.

✓
Brake system fault after driving through water. Diagnostic tool displayed P056024 and related communication faults. Checked the IPB module harness connector in the engine bay and found mud and water inside, with obvious oxidation and blackening on the power supply terminals (Pin 1/32). Cleaned the connector, applied conductive paste, and replaced the waterproof seal; fault cleared. Recommend checking the engine bay seals.
BYD DTC AI Analysis

Software version bug caused false positive (fixed via OTA)

✓
Multiple Song PLUS DM-i owners reported intermittent P056024 DTCs, but hardware inspections found no faults. A technical bulletin identified an overly sensitive power management strategy in IPB control unit software V1.2. Technicians upgraded the software to V1.4, optimizing the UBVR switching threshold from 12.0V to 11.5V. The fault rate dropped significantly after the upgrade.
BYD DTC AI Analysis

DC-DC converter output instability causes voltage fluctuations

✓
Fault code P056024 set when driving in HEV mode; EV mode operated normally. DC-DC output voltage measured fluctuating widely between 13.0-15.2V (should be stable at 14.0±0.2V). Inspection found loose DC-DC high-voltage input terminals causing power instability. Tightened the high-voltage connectors and updated the DC-DC control software. IPB power supply stabilized and the fault code has not returned.
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.