AU
C057A00

DTC C057A00 indicates an abnormally high voltage or a short to power (B+) in the IPB (Intelligent Power Brake) internal brake booster temperature sensor power supply circuit — Seal U

Braking System

DTC C057A00 indicates an abnormally high voltage or a short to power (B+) in the IPB (Intelligent Power Brake) internal brake booster temperature sensor power supply circuit.

Integrated within the electronic brake booster, this sensor monitors the operating temperature of the booster motor or electronic control unit in real time to prevent brake performance degradation or motor burnout from overheating.

The IPB-ECU logs a power supply short circuit fault when the sensor supply line (typically a 5V reference voltage) continuously exceeds the calibrated threshold (generally above 6.0V or reaching the 12V battery voltage).

This fault triggers the IPB system safety protection mechanism.

It may limit or completely disable brake assist, degrade ABS/ESP functions, and force the vehicle into Limp Home Mode.

The system retains only basic unassisted hydraulic braking.

This constitutes a severe fault affecting driving safety.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Damaged sensor wiring harness insulation causing a short circuit to 12V constant power (B+) or the ignition power wire.
  • 2Breakdown or internal short circuit of the brake booster internal temperature sensor element, causing abnormal continuity between the power supply pin and the ground pin or signal pin.
  • 3Fault in the internal 5V reference voltage regulation circuit of the IPB electro-hydraulic module, causing an abnormal increase in output voltage.
  • 4Water ingress, corrosion, or metallic debris in the sensor connector (usually located on the IPB assembly) causing abnormal continuity between terminals.
  • 5During vehicle accident repairs or modifications, crushed wiring or damaged insulation causes an incorrect connection or short circuit between the power wire and sensor signal wire.
What To Do
  • 1
    Safety preparation: Disconnect the high-voltage system service disconnect switch (for DM-i/EV models), disconnect the 12V battery negative terminal, and wait for more than 3 minutes to completely power down the IPB system and release residual pressure.
  • 2
    Fault confirmation: Connect the VDS or a dedicated diagnostic tool to read fault codes. Confirm C057A00 is a current fault (Present) and will not clear. Record freeze frame data. Check for accompanying C057B00 (signal short circuit) or IPB communication fault codes.
  • 3
    Wiring visual inspection: Inspect the wiring harness routing from the brake booster to the IPB module for abrasion, damaged insulation, or burn marks. Focus on harness fixing points and protective sleeves passing through the firewall, near the steering column, and in high-temperature areas of the front compartment.
  • 4
    Voltage measurement: Reconnect the battery, turn the ignition switch to the ON position, and measure the voltage between the temperature sensor connector power supply pin and ground. Normal voltage is 4.8-5.2V. If the reading is 12V or an abnormally high voltage, disconnect the connector and measure the voltage on the wiring harness side. If the voltage remains high, the wiring harness has a short circuit. If the voltage returns to normal, the sensor has an internal short circuit.
  • 5
    Harness continuity and insulation test: Disconnect the IPB module connector. Measure the continuity between the sensor power supply harness and the power supply (B+) (must have no continuity). Measure the insulation resistance to ground (must be greater than 10MΩ). Check the harness-to-body ground point for poor contact.
  • 6
    Sensor check: Measure the temperature sensor resistance (at room temperature, an NTC type typically measures 2-10kΩ and decreases as temperature rises). If the resistance is abnormally low (close to 0Ω) or infinite, and the wiring harness is normal, replace the brake booster assembly (the sensor is typically not available separately).
  • 7
    IPB module inspection: If the wiring harness and sensor are normal but the module output voltage remains abnormal (>5.5V), the IPB internal voltage regulator has failed. Replace the IPB electro-hydraulic brake module assembly.
  • 8
    Repair verification: After repairing the short circuit or replacing the faulty component, clear the fault code. Perform the IPB system self-check, brake line bleeding, and pedal position learning procedures. Conduct a road test to confirm the fault does not recur and the brake assist function operates normally.
Real-World Cases
BYD DTC AI Analysis

Song PLUS DM-i firewall wiring harness chafing caused short to power

✓
At 32,000 km, the ABS and ESP warning lights suddenly illuminated on the dashboard along with a brake system malfunction warning. The diagnostic scanner read current DTC C057A00. Inspection found the wiring harness retention clip at the firewall had come loose. Long-term friction between the harness and steering column dust boot chafed through the insulation, shorting the temperature sensor supply wire (5V) to the air conditioning compressor clutch power wire (12V). Repaired the damaged wiring, rerouted and secured the harness to eliminate interference, and resolved the fault.
Original source ↗
BYD DTC AI Analysis

BYD Seal IPB temperature sensor seal failure, internal short circuit

✓
After driving through water approximately 30 cm deep, the brake pedal became stiff. The scanner displayed DTC C057A00. Disassembled the IPB assembly and found the seal between the brake booster housing and the wiring harness connector had deteriorated. Water ingress damaged the internal temperature sensor element, shorting the power supply to ground. As the sensor is integrated within the electronic vacuum booster, replacing it separately would not guarantee sealing integrity. Replaced the entire electronic brake booster assembly, then performed IPB online coding and brake bleeding. Fault cleared.
Original source ↗
BYD DTC AI Analysis

BYD Dolphin IPB sensor connector water ingress and corrosion

✓
Continuous use during the rainy season triggered the ESC warning light and DTC C057A00. Inspection found significant green corrosion on the temperature sensor connector at the IPB module (located on the side of the module). Moisture between the terminals conducted electricity and caused abnormal power supply. Cleaned the connector terminals with electronic contact cleaner, dried them, applied specialized conductive paste and silicone grease for waterproofing, and wrapped the connector with waterproof tape for extra protection. Cleared the fault codes after repair and monitored for one week without recurrence.
BYD DTC AI Analysis

Han DM-i IPB module internal reference voltage abnormal

✓
The vehicle had no collision or water damage history. The brake assist failure warning appeared suddenly during normal operation. Multimeter measurement showed the temperature sensor supply voltage at 8.7V (normal: 5V). With the sensor disconnected, the IPB module output still measured 8.7V, confirming an internal 5V regulator circuit fault in the IPB. Replaced the IPB intelligent integrated brake module assembly and performed ECU online coding, longitudinal acceleration sensor calibration and brake bleeding using a dedicated diagnostic tool. The brake system returned to normal.
BYD DTC AI Analysis

BYD Song Pro DM-i wiring error after accident repair

✓
After front-end collision repairs at an external workshop, the instrument cluster displayed multiple brake system fault codes, including C057A00 and U-class communication faults. Inspection found technicians had misconnected the temperature sensor power wire to the CAN-H harness while restoring the front compartment wiring, causing network interference and voltage abnormalities. Corrected the harness connections per the factory wiring diagram and initialized the IPB system to clear the faults.
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: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.