AU
C00A800

This DTC indicates the Integrated Inertial Sensor (IIS) in the ESP (Electronic Stability Program) system lacks initial calibration, or the calibration data is abnormal or invalid — Qin Plus

Braking System

This DTC indicates the Integrated Inertial Sensor (IIS) in the ESP (Electronic Stability Program) system lacks initial calibration, or the calibration data is abnormal or invalid.

The Integrated Inertial Sensor integrates a high-precision MEMS accelerometer and gyroscope to monitor the vehicle’s longitudinal acceleration, lateral acceleration, and yaw rate in real time.

The ESP uses these core input signals for body stability control, anti-skid calculations, and Automatic Emergency Braking (AEB) decisions.

The ECU sets this DTC when it detects a significant deviation between the sensor output and the expected reference, when the calibration data area checksum validation fails, or when the installation attitude angle exceeds the permitted tolerance.

This condition forces the ESP system into a degraded mode, restricting or disabling functions such as the Anti-lock Braking System (ABS), Traction Control System (TCS), Vehicle Dynamics Control (VDC), and AUTOHOLD.

In extreme cases, this compromises driving safety.

3
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Reinstallation of the ESP/IPB control unit assembly following accident repairs, chassis disassembly, or a collision altered the installation angle or levelness, causing the inertial sensor to lose its reference attitude.
  • 2The vehicle chassis sustained a severe impact (such as bottoming out, a deep pothole impact, or a collision), causing a slight shift in the sensor's physical position or zero-point drift in the internal MEMS chip.
  • 3Failed to perform the initial Sensor Calibration procedure after replacing the ESP hydraulic modulator assembly, or failed to keep the vehicle absolutely level during calibration.
  • 4Integrated inertial sensor internal fault (MEMS chip aging, cold solder joint, internal IC damage) or corrupted ECU internal EEPROM data, resulting in unreadable calibration parameters or verification failure.
  • 5Control unit software version defect, flashing error, or abnormal power loss causing calibration data area corruption.
What To Do
  • 1
    Pre-inspection preparation: Park the vehicle on level ground (recommended hoist platform levelness error <0.5°), center the steering wheel, check the ESP/IPB control unit mounting bracket for deformation, verify the fixing bolt torque meets specification (usually 8-12Nm), and confirm the mounting surface is free of debris and the control unit is level.
  • 2
    Fault confirmation: Connect a dedicated diagnostic tool such as BYD VDS or Launch X-431, enter the ABS/ESP system, read and record all fault codes, and check for C00A800 and accompanying faults such as C006102 (lateral acceleration sensor) and C006202 (longitudinal acceleration sensor).
  • 3
    Software calibration: Select 'Special Functions' → 'Inertial Sensor Calibration' (Sensor Calibration/IIS Calibration). Follow the prompts, keep the vehicle stationary, do not press the brake pedal, and do not turn the steering wheel. Execute the calibration procedure (usually 30-60 seconds) until the diagnostic tool displays 'Calibration successful'.
  • 4
    Function check: Clear all fault codes. Turn off the vehicle, wait 5 minutes, then power on again. Confirm C00A800 does not reappear. Perform a road test (including straight-line driving and moderate steering). Verify the ESP warning light turns off and the lateral/longitudinal acceleration values in the data stream are within a reasonable range (close to 0±0.1g when stationary, changing normally during steering).
  • 5
    Hardware replacement: If calibration fails repeatedly, the fault recurs intermittently after calibration, or internal circuit fault codes are present, replace the ESP hydraulic modulator assembly with ECU. After replacement, perform the calibration and brake system bleeding procedures.
Real-World Cases
BYD DTC AI Analysis

Seal ESP warning light stays on — calibration skipped after chassis repair

✓
2023 Seal, 12,000 km. After starting, the ESP and ABS warning lights stayed on, along with the traction control indicator. VDS scan showed fault code C00A800 (Integrated Inertial Sensor Not Calibrated) accompanied by C006102. Inspection found no collision damage, but revealed underbody protection work at an unauthorized shop where the ESP assembly had been removed. Reinstalled the ESP unit to the standard torque of 10 Nm, ensured it was level, then performed the sensor calibration. Fault cleared; road test confirmed all functions normal.
Original source ↗
BYD DTC AI Analysis

E5 sensor calibration lost after collision repair

✓
Following front collision repairs on a 2019 E5, the dashboard displayed "Check ESP System" with DTC C00A800. Inspection found the ESP control unit had been removed and the mounting bracket slightly deformed. Straightened the bracket, ensured the control unit was level, then performed sensor calibration using VDS. Initial calibration indicated "excessive vehicle tilt angle". Leveled the lift platform and recalibrated successfully. Fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD Dolphin: Intermittent multi-system warning lights illuminated — software refresh resolved it

✓
2022 BYD Dolphin intermittently triggered simultaneous ESP, ABS and TPMS warning lights while driving. After restarting, some lights cleared but the ESP light remained on. Dealer diagnostics found DTC C00A800 and related communication faults. Technician checked ESP assembly installation and found no issues. No hardware replaced. Performed inertial sensor calibration via VDS and flashed IPB control unit software to the latest version (V2.3.5 or above). Fault has not recurred. Early software version defect caused abnormal sensor self-check.
Other Qin Plus 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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Qin Plus →Qin Plus overview →
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.