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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.

5
Cases Logged
Real-World Cases
BYD DTC AI Analysis

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

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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

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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.

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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)

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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

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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
B1108For the BYD Song MAX (2017–2019), DTC B1108 indicates a short circuit in the PM2.5 air quality detection module (dust sensor) or its wiring harness. The sensor uses laser scattering to detect in-cabin and outside PM2.5 concentrations and transmits data to the HVAC ECU via the LIN bus or an analog signal. Short circuit conditions include: 1) Sensor power supply wire (+5V/+12V) shorted to ground 2) Signal wire shorted to power or ground 3) Short circuit in the sensor's internal photoelectric detection circuit This fault prevents the automatic climate control from switching between fresh air and recirculation based on air quality. The system enters fail-safe mode (typically forced recirculation). Severe short-circuit current can destroy the HVAC ECU sampling circuit. The system classifies this as a Level 3 severe fault and restricts vehicle operation to prevent electrical fires or controller damage. For other BYD models (such as the Qin EV, E5, and Song DM), B1108 indicates a driver-side sunload sensor fault, reflecting differences in DTC definitions across models.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.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.
Data confidence: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.