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 — Seal U

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.

The P056024 fault code on the Seal U indicates that the Integrated Power Brake system has detected a switch, or attempted switch, to its backup voltage regulator power supply. Severity is medium, as braking support functions such as ABS, ESC, or emergency braking may be affected. Common causes include a weak 12V battery or loose, corroded IPB power connections. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
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Cases Logged
5
Causes
Likely Causes — Seal U
  • 1An aging or undercharged low-voltage battery (12V battery) causes a sudden voltage drop during startup or driving, triggering backup mode.
  • 2Poor contact, loose connections, or corrosion in the IPB module power supply circuit, causing intermittent supply voltage interruption.
  • 3DC-DC converter fault (DM-i models) causing unstable high-voltage to low-voltage output that fails to meet IPB operating voltage requirements.
  • 4IPB electro-hydraulic module internal power management circuit or UBVR changeover relay fault, 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, leaving the system voltage at a critical level.
What To Do
  • 1
    Use the VDS2000/3000 diagnostic tool to read the complete fault code stream, determine if 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 fastening. Measure the voltage drop; it must be <0.1V.
  • 4
    Disconnect the IPB module connector. Inspect the terminals for backout, oxidation, or water ingress. Measure the power supply terminal voltage stability. 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 Seal U Fault Codes
B110913DTC B110913 indicates an open signal circuit for the PM2.5 rapid detector (in-cabin air quality sensor). This sensor typically mounts inside the air conditioning system intake duct. It monitors in-cabin PM2.5 concentration in real time and provides data to the automatic air conditioning system for intelligent control of the air purification function. The BYD diagnostic protocol uses sub-code '13' to specifically indicate an open signal circuit. Although this fault theoretically affects a comfort feature, BYD Qin series vehicles classify it as a Level 3 (severe) fault. This classification occurs because the air conditioning system interacts with the battery thermal management system (e.g., monitoring battery cooling intake air quality). The fault can disable the automatic air conditioning mode and prevent the air purification function from operating. In extreme cases, it affects the battery compartment intake air quality assessment, triggering the 'repair immediately' strategy.B110AThis DTC indicates interrupted CAN bus communication or abnormal data between the air conditioning control unit (ACU) and the PM2.5 air quality sensor. The PM2.5 sensor monitors particulate concentration inside and outside the vehicle and provides the basis for purification control in the automatic air conditioning system. The ACU triggers this fault if it fails to receive a valid CAN message from the sensor within the specified period (usually 100-500 ms), if message verification fails, or if the signal frame times out. Although this fault does not affect vehicle driving safety, it disables the automatic air purification function. The air conditioning system cannot automatically switch between recirculation and fresh air modes or activate the air purification mode based on air quality. A persistent fault may restrict the thermal management strategy.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173712DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Common problems reported for Seal U →Seal U 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.