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C054100

DTC C054100 indicates the analog voltage signal from the second pressure sensor (typically the accumulator pressure sensor or master cylinder pressure monitoring sensor) inside the IPB (Intelligent Power Brake) module exceeds the ECU-calibrated upper threshold (typically >4 — Atto 3

Braking System

DTC C054100 indicates the analog voltage signal from the second pressure sensor (typically the accumulator pressure sensor or master cylinder pressure monitoring sensor) inside the IPB (Intelligent Power Brake) module exceeds the ECU-calibrated upper threshold (typically >4.8V or a corresponding pressure exceeding the system safety limit, such as >22MPa).

In the Bosch IPB system used by BYD, this sensor uses the piezoresistive effect to convert hydraulic pressure into a 0.5-4.5V linear voltage signal.

The ECU logs an "Out of Range High" fault when it detects this signal voltage remains above the valid physical range over multiple consecutive drive cycles (i.e., the sensor reports an excessively high pressure regardless of actual braking conditions).

This fault triggers the IPB system to enter a safety degradation mode: it disables regenerative braking, limits ESC functions, maintains basic hydraulic brake assist, and illuminates the ABS/ESC warning lamps.

If Sensor 2 monitors accumulator pressure, sustained high pressure may prevent the motor pump from starting or cause the pressure relief valve to remain open continuously, affecting brake pedal feel and response speed.

5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1A ruptured pressure sensor internal diaphragm or shorted circuit locks the signal output near the 5V reference voltage (sensor component fault).
  • 2Water ingress, pin oxidation, or backed-out pins at the IPB wiring harness connector (usually near the engine compartment firewall), causing the sensor signal wire (SIG) to short to the power supply wire (+5V or +12V).
  • 3IPB accumulator internal pressure rises abnormally and fails to relieve (e.g., accumulator pressure holding valve stuck closed or oil return port blocked), causing physical pressure to continuously exceed the sensor measuring range.
  • 4Internal signal acquisition circuit fault in the IPB control unit (ECU), such as a damaged ADC conversion chip or abnormally high 5V reference voltage regulator output, causing the ECU to misread sensor signals.
  • 5Severe brake fluid contamination (such as excessive water content, mixed low-boiling-point DOT3 fluid, or metal debris) blocks the sensor pressure port or corrodes the diaphragm, generating a false high-pressure signal.
What To Do
  • 1
    Use VDS2000 or a dedicated BYD diagnostic tool to read the DTC freeze frame data. Record the vehicle speed, brake pedal travel, motor pump operating status, and specific pressure values of Pressure Sensor 1 (master cylinder) and Sensor 2 (accumulator) at the time of the fault to determine if the high pressure is genuine or a false high signal.
  • 2
    Check that the brake fluid level is between the MAX and MIN marks. Inspect the brake fluid color and clarity. If the fluid is cloudy, dark, or contains suspended particles, completely replace it with brake fluid meeting the DOT4 standard (dry boiling point ≥230°C) and perform a circulation flush of the IPB system.
  • 3
    Disconnect the 16-pin or 24-pin harness connector from the IPB module (located on top of the module). Visually inspect the sealing ring for damage and the pins for bends or burns. Use a multimeter to measure the resistance from the Pressure Sensor 2 signal pin (usually pin X; refer to the wiring diagram) to ground and to +B (12V). Resistance should be >10 MΩ. Measure continuity to the corresponding pin at the ECU; resistance should be <1 Ω.
  • 4
    Reconnect the wiring harness. Access 'IPB System -> Data Stream' on the diagnostic tool and read 'Accumulator Pressure' and 'Master Cylinder Pressure'. Without pressing the brake pedal, the accumulator pressure should be 12-18 MPa. If the accumulator pressure reads >20 MPa or the voltage is >4.8 V while the master cylinder pressure is normal (approximately 0.1-0.3 MPa), Sensor 2 or the accumulator assembly is faulty.
  • 5
    Perform the IPB system bleeding procedure: First, use the diagnostic tool to perform 'motor pump bleeding' (to remove air bubbles inside the accumulator), then bleed the wheel cylinders in the following order: right rear -> left rear -> right front -> left front. Observe the Pressure Sensor 2 value during the bleeding process. Normally, the value changes linearly between 0-20MPa. If the value does not change or remains consistently high, proceed to the next step.
  • 6
    Check IPB power supply and ground: measure module power pin voltage (should be 12V±0.5V) and measure ground resistance (should be <0.5Ω). If the power supply is normal but pressure data is abnormal, reflash the IPB control unit software (update to the latest version) and calibrate the system (including pressure sensor zero-point and range calibration).
  • 7
    If the above steps fail to restore operation, and wiring short circuits and brake fluid issues are ruled out, the internal sensor or hydraulic circuit of the IPB electro-hydraulic module is faulty. Replace the IPB assembly (including ECU). After replacement, perform: ① Coding configuration (write vehicle VIN and configuration parameters); ② Linear valve calibration; ③ Pedal travel sensor calibration; ④ Four-wheel brake bleeding.
Real-World Cases
BYD DTC AI Analysis

Song PLUS DM-i IPB pressure sensor short circuit after wading in heavy rain

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A 2021 Song PLUS DM-i drove through standing water during heavy rain, and the instrument panel simultaneously lit up the ABS, ESP and brake system warning lights. VDS retrieved DTCs C054100 (Pressure Sensor 2 Out of Range High) and C054200 (Pressure Sensor 2 Circuit Malfunction). Technicians removed and inspected the IPB wiring harness connector near the left front fender, finding a deteriorated seal had allowed water in with visible staining inside the connector. They measured only 1.2kΩ between the pressure sensor signal pin and the 5V reference power pin (severe short). They cleaned the connector interior with anhydrous ethanol, dried it with a high-pressure air gun, fitted a new waterproof seal, and applied waterproof insulating silicone grease to the harness connector. After reconnecting, they cleared the DTCs and the IPB system passed its self-test, resolving the fault.
BYD DTC AI Analysis

Unauthorised brake fluid replacement contaminated the sensor.

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After routine maintenance, the brake fluid was changed at a non-authorized shop. Three days later, fault code C054100 appeared with a hard brake pedal and loss of energy recovery. Technicians found the shop had used incorrect substandard DOT3 fluid (dry boiling point only 205°C) containing impurities. Gum deposits in the fluid blocked the pressure port of IPB pressure sensor 2 (accumulator pressure monitoring), causing the sensor to read high pressure continuously. Solution: Completely drained all old brake fluid, flushed the IPB hydraulic circuit three times with dedicated cleaning fluid, replaced it with BYD genuine DOT4 brake fluid, and performed the complete IPB bleed procedure (motor pump bleed plus four-wheel bleed). After cleaning, sensor pressure values returned to normal and the fault code cleared.
BYD DTC AI Analysis

IPB module internal sensor zero drift

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Parked overnight, the vehicle displayed a brake system fault immediately on cold start. Only DTC C054100 set. Live data: with the brake pedal released, pressure sensor 1 (master cylinder) read 0.2 MPa (normal), but pressure sensor 2 (accumulator) read 25.5 MPa—exceeding the 18 MPa upper limit—and stayed fixed regardless of pedal movement. Checked IPB power supply, ground and wiring harness continuity; all normal. Internal fatigue of the pressure-sensitive diaphragm in pressure sensor 2 caused zero drift, locking the output signal at a high voltage. The IPB is integrated and the sensor is not serviceable separately, so replaced the IPB electro-hydraulic brake assembly with ECU, then performed control unit coding, linear valve calibration and pedal calibration. Fault resolved completely.
BYD DTC AI Analysis

Aftermarket underbody skid plate damaged wiring harness, causing signal short circuit

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After the owner fitted engine and underbody protection plates, the dashboard displayed codes C054100 and C054200 after approximately 500 km. Raising the vehicle revealed the protection plate mounting screws were too long and had pierced the IPB wiring harness corrugated tube, crushing the pressure sensor 2 signal wire and the 12 V constant power wire together and causing a short circuit. Repaired the damaged wiring by cutting out the damaged section, re-soldering the connections and insulating with heat-shrink tubing. Adjusted the protection plate screw lengths and fitted rubber washers. Rerouted the wiring harness to avoid contact with sharp metal edges. Post-repair measurement showed the sensor signal voltage had returned to normal (0.5-4.5V varying with pressure). Cleared the fault codes and the system operates normally.
BYD DTC AI Analysis

IPB control software calibration data fault

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Following the OTA update, the vehicle set fault code C054100 on the next startup. The driver noted normal braking performance with no shudder or hard pedal. VDS revealed the IPB software update had interrupted, causing loss of pressure sensor calibration data. The ECU had incorrectly set pressure sensor 2's upper threshold below the actual value. Solution: Checked the BYD service bulletin and confirmed this VIN needed the IPB control unit software flashed to the latest version (must be higher than 3.8.2). After flashing, performed 'sensor zero-point calibration' and 'accumulator pressure learning'. The fault code cleared automatically and the data stream showed pressure values back in normal range.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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.