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 — Atto 8

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.

The C00A800 fault code on the Atto 8 indicates the ESP system’s Integrated Inertial Sensor has missing, invalid, or abnormal calibration data. Severity is medium because ESP-related functions such as ABS, traction control, stability control, and AUTOHOLD may be reduced or disabled. Common causes include ESP/IPB unit reinstallation after repairs or a strong chassis impact changing the sensor angle. Visit an authorised dealer for inspection and recalibration. Typical repair cost data is available from 3 recorded cases.
3
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Reinstalling the ESP/IPB control unit assembly after accident repairs, chassis removal/installation, or a collision altered the installation angle/level, causing the inertial sensor to lose its reference attitude.
  • 2Severe impact to the vehicle chassis (such as bottoming out, a deep pothole impact, or a collision) causing slight physical displacement of the sensor or zero-point drift in the internal MEMS chip.
  • 3Failure to perform the initial Sensor Calibration procedure for the new part after replacing the ESP hydraulic modulator assembly, or failure to keep the vehicle perfectly level during calibration.
  • 4Internal fault in the integrated inertial sensor (MEMS chip aging, cold solder joint, internal IC damage) or corrupted data in the ECU internal EEPROM memory, resulting in unreadable calibration parameters or verification failure.
  • 5Defective control unit software version, flashing error, or abnormal power loss corrupting the calibration data area.
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, and verify the fixing bolt torque meets the specification (usually 8-12 Nm). 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, and read and record all fault codes. 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 to 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 verification: Clear all fault codes. Power off the vehicle, wait 5 minutes, then power on again and 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 Atto 8 Fault Codes
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.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.