AU
C002100

DTC C002100 indicates the IPB (Integrated Power Brake) detects brake master cylinder pressure (booster pressure) below the system-calibrated normal operating threshold — Atto 3

Braking System

DTC C002100 indicates the IPB (Integrated Power Brake) detects brake master cylinder pressure (booster pressure) below the system-calibrated normal operating threshold.

In BYD models equipped with the IPB system, such as the Song PLUS DM-i, a motor-driven hydraulic pump generates brake assist, replacing the conventional vacuum booster.

When the internal IPB pressure sensor detects the master cylinder pressure fails to reach the target value within the specified time or remains below the safety threshold, the ECU sets this fault code and illuminates the ABS/ESP warning light.

This condition can cause a hard brake pedal (loss of assist), increased braking distance, Automatic Emergency Braking (AEB) deactivation, and limited energy recovery, compromising driving safety in severe cases.

This functional braking system fault can result from an internal IPB hydraulic circuit leak, pressure sensor signal drift, reduced motor/pump assembly efficiency, or abnormal ECU control logic.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1IPB electro-hydraulic module internal master cylinder pressure sensor fault, signal drift, or poor circuit contact (connector oxidation, backed-out pins)
  • 2Wear, binding, or drive circuit fault in the IPB motor or hydraulic pump assembly, resulting in slow or insufficient pressure build-up.
  • 3Brake fluid leakage prevents the system from maintaining pressure (aging IPB unit seal, master cylinder seal failure, or loose line fittings)
  • 4Outdated IPB ECU software version or hardware fault (damaged internal power supply circuit, failed solenoid valve driver chip)
  • 5Brake fluid level too low, degraded fluid quality (excessive water content), or failure to perform the correct bleeding/calibration procedure after replacement.
What To Do
  • 1
    Use the BYD VDS2000/3000 diagnostic tool to read fault codes and freeze frame data. Record vehicle speed, master cylinder pressure, motor status, and ambient temperature at the time of the fault.
  • 2
    Visually check if the brake fluid level is between MAX and MIN. Inspect the IPB unit, brake lines, and calipers for signs of fluid leakage.
  • 3
    Read the IPB live data stream. Compare the 'actual master cylinder pressure' with the 'target pressure'. Verify the pressure rises linearly while the motor is running (normally, pressure builds rapidly within 1-2 seconds after the motor starts).
  • 4
    Check the IPB module electrical connections: measure the supply voltage (constant +B, should be 12V ± 0.5V), ground resistance (should be < 1Ω), and CAN-H (approx. 2.6-2.8V) and CAN-L (approx. 2.2-2.4V) signal voltages.
  • 5
    Perform the IPB system bleeding procedure (use the diagnostic tool to access the 'Brake System Bleeding' function; this automatically activates the motor to bleed fluid in the sequence of front left - front right - rear left - rear right. Never use the traditional pedal-pumping method).
  • 6
    If pressure remains abnormal, update the IPB ECU software. If unsuccessful, replace the IPB electro-hydraulic module assembly with ECU. After replacement, perform 'End of Line Configuration', 'Sensor Calibration', and 'Longitudinal Acceleration Sensor Calibration'.
Real-World Cases
BYD DTC AI Analysis

BYD Qin PLUS DM-i - IPB pressure sensor wiring poor contact

✓
Symptoms: After starting the vehicle, the instrument cluster displayed 'Check ESP System' and 'Check Brake System'. The brake pedal felt noticeably harder. Diagnostic tool retrieved fault code C002100 (Brake Booster Pressure Too Low). Diagnostic process: Used VDS to read brake system data stream. Master cylinder pressure read 0kPa (normal idle should be 50-70bar), confirming no sensor signal output. Inspected IPB module connector and found the plug loose with pins showing white oxidation. Measured sensor supply voltage: 12V power normal, ground normal, but signal line voltage abnormal. Diagnosed as poor connector contact interrupting the signal. Solution: Cleaned IPB connector pins with electronic cleaner, applied conductive grease to prevent corrosion, reseated the plug firmly and secured the wiring harness with cable ties. Cleared fault codes and test drove. Master cylinder pressure data returned to normal. Fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD Song Pro DM - IPB internal pressure sensor damaged

✓
Symptoms: While driving, the brake pedal suddenly hardened. Required great effort to depress. ABS and ESP warning lights illuminated simultaneously. Owner described the sensation as "like there's no assist". Diagnostic scan showed DTC C002100; could not clear. Diagnostic process: Started vehicle and listened for IPB motor operation. Motor ran normally with noticeable vibration, ruling out a power supply fault. Data stream showed normal motor current but pressure value stayed at 0, unchanged during motor operation. Measured IPB pressure sensor signal output: constant 0V. Determined internal sensor damage. Solution: Replaced IPB electro-hydraulic module assembly with integrated ECU (part number varies by vehicle configuration). After replacement, bled system, performed coding and calibration. Fault code cleared. Brake assist returned to normal.
Original source ↗
BYD DTC AI Analysis

BYD e5 450 - IPB motor controller fault with associated warnings

✓
Symptoms: EV would not enter READY mode (unable to shift into gear or drive). Instrument cluster showed "Brake System Fault". Vehicle controller stored DTCs C002100 (Brake Booster Pressure Too Low) and C002200 (Pressure Sensor Signal Too Low). Diagnosis: EVs rely on the IPB to generate brake assist. Checked IPB fuse and relay first; both normal. Applied direct power to the IPB motor; motor did not run. IPB internal motor controller failed, preventing pressure build-up. Pressure sensor set C002100 because it detected no pressure; this is a secondary fault. Root cause is the inoperative IPB motor. Solution: Replaced IPB electro-hydraulic module assembly with ECU. After replacement, IPB motor runs normally, pressure builds, sensor signal returns to normal, and vehicle starts normally.
Original source ↗
BYD DTC AI Analysis

BYD Tang DM – IPB system seal ring aged and leaking

✓
Symptoms: Hard brake pedal on cold start. Braking returns to normal after driving 5–10 minutes or once warm. Intermittent fault. Scan tool occasionally logs DTC C002100, sometimes accompanied by a "hydraulic pump operation timeout" warning. Diagnosis: Live data showed master cylinder pressure only reached 20 bar when cold (below the normal 50 bar+). The IPB motor ran continuously for over 30 seconds (normally it reaches target pressure and stops within 10 seconds). Inspection found slight oil seepage at the connection between the IPB body and master cylinder. When cold, the rubber seal contracts and causes internal leakage; the seal expands when warm, improving sealing. The pressure sensor detected slow pressure build-up and triggered the fault code. Repair: Replaced the IPB assembly (internal seals are not available separately) and replaced the brake fluid. After replacement, cold-start pressure build-up time returned to normal (reaching 50 bar in approximately 3 seconds).
Original source ↗
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.