AU
C053D00

This fault code indicates the IPB (Intelligent Integrated Braking System) detects the hydraulic pressure value from the brake master cylinder pressure sensor falls outside the system-calibrated normal threshold range (too high or too low) — Seal U

Braking System

This fault code indicates the IPB (Intelligent Integrated Braking System) detects the hydraulic pressure value from the brake master cylinder pressure sensor falls outside the system-calibrated normal threshold range (too high or too low).

The IPB system monitors the driver’s braking intent and hydraulic circuit status in real time via the master cylinder pressure sensor.

The system logs a pressure out-of-range fault if the pressure signal voltage falls outside the valid 0.5-4.5V range, or if the pressure value mismatches the pedal travel and wheel cylinder pressure logic.

This fault triggers a degraded protection mode, which may limit ABS/ESC functions, disable automatic emergency braking, or cause abnormal brake pedal feel, severely compromising driving safety.

4
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Master cylinder pressure sensor inside the IPB integrated module drifted or damaged, causing abnormal signal output.
  • 2Brake hydraulic system leak (lines, wheel cylinders, or aged IPB unit sealing ring) preventing the system from building or maintaining actual pressure.
  • 3Severely low, degraded, or aerated brake fluid causing abnormal pressure transmission and sensor reading deviations.
  • 4A sticking hydraulic valve body or motor drive fault inside the IPB electro-hydraulic control unit causes pressure regulation to exceed the calibrated range.
  • 5Water ingress, corrosion, loose pins, or poor shielding in the pressure sensor wiring harness connector causing signal voltage fluctuations.
What To Do
  • 1
    Safety check and initial assessment: Verify the brake fluid level is between MAX and MIN, check the instrument cluster warning light status (ABS/ESC lights remain illuminated), and perform a road test to verify normal brake pedal travel and braking force.
  • 2
    Diagnostic tool readout: Use VDS or Launch X431 to read complete fault codes and view freeze frame data (record pressure value, pedal travel, and vehicle speed when the fault occurred). Analyze whether the pressure is too high (>20MPa abnormal) or too low (<0.5MPa abnormal).
  • 3
    Data stream analysis: Read the master cylinder pressure sensor voltage in real time. The normal range is 0.5-4.5V, corresponding to 0-25MPa. Press the pedal and verify the pressure changes linearly to rule out sensor drift.
  • 4
    Circuit inspection: Disconnect the IPB module connector. Measure the resistance of the pressure sensor power supply (5V reference voltage), ground, and signal wires. Check the wiring harness for an open circuit or a short to ground/power. Inspect the connector pins for oxidation.
  • 5
    Hydraulic system check: Inspect all four brake calipers and lines for leaks. Run the bleeding procedure to confirm the system is free of air. If the fluid level is normal but the system fails to build pressure, perform a sealing test on the IPB hydraulic unit.
  • 6
    Component replacement: If diagnostics confirm a faulty internal IPB sensor or hydraulic unit, replace the entire IPB electro-hydraulic brake assembly (do not attempt individual repairs). After replacement, perform coding configuration and calibrate the longitudinal acceleration sensor.
  • 7
    System calibration and verification: After replacement, perform the brake system bleeding procedure (use the diagnostic tool to perform motor bleeding). Clear the fault codes, perform an ESC dynamic test and emergency braking verification, and confirm the data stream pressure value is within the normal range.
Real-World Cases
BYD DTC AI Analysis

Song PLUS DM-i IPB pressure sensor intermittent drift

✓
ABS/ESC warning light on instrument panel illuminates intermittently; DTC C053D00 sets intermittently. Scan tool freeze frame shows master cylinder pressure signal voltage at 4.8V (out of range), with pressure data occasionally jumping above 25MPa when pressing brake pedal. Inspected wiring harness; no faults found. Brake fluid level normal. Diagnosed as IPB internal master cylinder pressure sensor thermal drift failure. Replaced IPB assembly, then performed bleed procedure and sensor calibration. Fault resolved.
BYD DTC AI Analysis

Brake fluid leak caused master cylinder pressure to drop too low

✓
The owner reported the brake pedal felt soft and the instrument cluster displayed a brake system fault. Retrieved DTC C053D00 (current status). Data stream showed master cylinder pressure at 0.1 MPa (abnormally low); pedal travel sensor readings were normal. Inspection found the left rear wheel cylinder leaking with brake fluid level near MIN. Replaced the wheel cylinder, topped up brake fluid and performed the IPB bleed procedure. Pressure returned to normal and the DTC cleared.
BYD DTC AI Analysis

Stuck IPB hydraulic valve caused pressure to exceed the upper limit

✓
While driving normally, the vehicle suddenly triggered a warning and the ESC light stayed on. Read DTC C053D00 (master cylinder pressure out of range). Live data showed 12 MPa master cylinder pressure with the pedal released (abnormally high). Pedal return checked normal; no brake drag. The master cylinder isolation valve inside the IPB stuck in the closed position, preventing residual pressure release. Replaced the IPB electro-hydraulic module assembly. Fault resolved.
BYD DTC AI Analysis

Water ingress in the wiring harness connector caused signal abnormality

✓
After driving in rain, the brake system warning light illuminated with DTC C053D00. The IPB module connector had internal water and oxidation; the pressure sensor signal pin was corroded. Cleaned the connector and applied conductive paste. Signal line voltage measured normal at 2.3V static. Road tested for three days with no recurrence. Check engine bay sealing to prevent rainwater splashing onto the IPB connector.
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.