AU
C051D01

DTC C051D01 indicates an abnormal calibration status of the inertial measurement unit (IMU) inside the IPB (Integrated Power Brake) — Seal U

Braking System

DTC C051D01 indicates an abnormal calibration status of the inertial measurement unit (IMU) inside the IPB (Integrated Power Brake).

Specifically, the yaw rate sensor or longitudinal acceleration sensor reference data is lost, offset, or invalid.

Integrated inside the IPB control module, this sensor monitors the vehicle’s rotational yaw rate about the vertical axis and its longitudinal acceleration in real time.

It provides the core input signal the ESP electronic stability control system uses to calculate vehicle dynamic attitude.

The IPB sets this code when it detects the sensor output deviates from the expected calibration reference beyond the threshold, or when it loses the stored calibration parameters.

This limits ESP functionality or triggers limp mode; however, normal hydraulic braking usually remains unaffected.

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Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Failure to perform the IMU sensor calibration procedure after replacing the IPB assembly, disconnecting the battery, or prolonged vehicle battery depletion, resulting in lost calibration data.
  • 2A loose IPB control module mounting bracket, insufficient retaining bolt torque, or external impact to the module caused the physical reference of the internal inertial sensor to shift.
  • 3IPB control program updated after a vehicle software upgrade (OTA or diagnostic tool) without simultaneously resetting or matching the calibration data.
  • 4Hardware aging of the Inertial Measurement Unit (IMU) inside the IPB, chip overheating, or poor PCB solder joints causes signal drift beyond the self-check tolerance.
  • 5Extreme electromagnetic interference or power supply voltage fluctuations (such as jump-starting or abnormal generator voltage regulation) corrupting memory calibration parameters.
What To Do
  • 1
    Use a BYD dedicated diagnostic tool (VDS or ED400) to read the complete IPB system fault codes and freeze frame data. Confirm if related fault codes such as C006A02 (signal error) or C00A800 (not calibrated) accompany C051D01.
  • 2
    Visually inspect the IPB control module for external damage and verify the module mounting bracket is not deformed. Tighten the fixing bolts to the specified torque (usually 8-10 N·m) and ensure the module mounting surface is parallel to the vehicle body reference surface.
  • 3
    Measure the IPB supply voltage (B+ to ground) and ensure the battery voltage is ≥12V with no loose connections; check the CAN-H and CAN-L communication line voltage (2.5V±0.1V) and terminating resistance (approx. 60Ω).
  • 4
    Perform the sensor calibration procedure: Park the vehicle on level ground, center the steering wheel (within ±5°), and close all doors. Access the IPB system on the diagnostic tool, select the 'Sensor Calibration' or 'IMU Calibration' function, and complete the yaw rate sensor zero-point calibration and longitudinal acceleration sensor calibration in sequence (some models require simultaneous pressure sensor calibration).
  • 5
    After successful calibration, clear the fault code and perform a dynamic road test including straight-line acceleration, constant-speed cruising, left and right turns (to generate yaw moment), and emergency braking. Verify the instrument cluster ESP/ABS warning light turns off and the system does not intervene abnormally.
  • 6
    If the calibration procedure aborts or fails, or the fault code returns, diagnose an internal IPB hardware fault and replace the IPB assembly. After replacement, configure the new module coding, write the VIN, and perform a complete sensor calibration.
Real-World Cases
BYD DTC AI Analysis

ESP warning light on after suspension repair (yaw rate sensor not calibrated)

✓
After the 4S shop replaced the front shock absorbers and lower control arms on a Song Plus DM-i, the instrument cluster showed a steady ESP warning light and the steering wheel felt abnormal self-centering torque when turning. VDS read IPB system fault code C051D01; freeze frame data showed the fault occurred at 0 km/h. Inspection found technicians disconnected IPB-related wiring harnesses during the chassis repairs and skipped sensor calibration afterward. We performed the "Yaw Rate Sensor Zero Position Calibration" procedure on level ground, cleared the fault codes after calibration, and road-tested 5 km to confirm ESP function returned to normal and the warning light went out.
Original source ↗
BYD DTC AI Analysis

IPB system warning after software upgrade (calibration data lost)

✓
After an OTA software update, the Qin PLUS DM-i started up the next day with the ESP and ABS warning lights and a 'Check Brake System' alert on the instrument cluster, and entered limp mode. The diagnostic scanner showed IPB system DTCs C051D01 (Yaw Rate Sensor Calibration Error) and C006A02 (Yaw Rate Sensor Signal Error). Technicians determined the IPB control logic had updated during the software upgrade, but the internal IMU calibration data had not synchronized. Using an ED400 diagnostic tool, they accessed the IPB system and ran the 'Integrated Sensor Calibration' procedure (longitudinal acceleration, yaw rate, and master cylinder pressure sensor calibration). The system passed self-checks after calibration. They cleared the fault codes and road-tested; brake force distribution and stability control functioned normally.
Original source ↗
BYD DTC AI Analysis

IPB internal IMU hardware failure caused calibration failure.

✓
A Song PLUS DM-i with 30,000 km and no collision or repair history sat stationary overnight. The next morning at startup, the dashboard suddenly showed an ESP warning. Only DTC retrieved: C051D01. Freeze frame showed the vehicle completely stationary when the fault occurred, battery voltage normal at 12.4V. Attempted sensor calibration; the scan tool returned 'Calibration failed - sensor signal out of tolerance'. Checked IPB power supply and ground—both normal. Diagnosed as internal Inertial Measurement Unit (IMU) chip hardware fault or dry solder joint in the IPB, causing permanent signal baseline offset. Replaced the IPB assembly (part number 6A-3630100). After replacement, performed coding, VIN configuration, and sensor calibration on the new module. Fault completely resolved.
Original source ↗
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.