AU
C019604

This DTC indicates a functional fault in the Inertial Measurement Unit (IMU) integrated within the ESP (Electronic Stability Program) hydraulic modulator — Atto 3

Braking System

This DTC indicates a functional fault in the Inertial Measurement Unit (IMU) integrated within the ESP (Electronic Stability Program) hydraulic modulator.

This MEMS-based sensor assembly integrates a Yaw Rate Sensor and a Lateral G-Sensor.

It monitors the vehicle's real-time rotational angular velocity around the vertical axis and lateral acceleration to provide critical vehicle dynamic attitude parameters for the ESP, TCS, HHC, and AEB systems.

Sub-code '04' specifically indicates a signal circuit/range/performance fault or an internal self-test failure.

Possible causes include: 1) Physical damage to the sensor hardware (internal silicon structure fracture or cracked solder joints); 2) Operating temperature outside the rated range (-40°C to +85°C); 3) Signal output exceeding valid thresholds (e.g., yaw rate ±75°/s or lateral acceleration ±1.5g); 4) ECU internal A/D converter or power management circuit fault.

This fault causes complete failure of the vehicle stability control system.

It creates a loss-of-control risk under extreme conditions (such as high-speed cornering or emergency obstacle avoidance) and may compromise the accuracy of the brake energy recovery strategy.

This is a safety-critical fault requiring immediate repair.

3
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Physical damage, aging, or poor internal solder joints of the inertia sensor chip inside the ESP hydraulic modulator assembly (HECU), causing signal drift or complete loss of output.
  • 2Sensor power supply circuit fault: Includes unstable constant power (B+) or ignition power (IG1) voltage, and excessive ground circuit resistance (>1Ω), causing the sensor reference voltage (typically 5V) to drift.
  • 3Module installation issue: Angle between the mounting surface and the vehicle horizontal plane exceeds tolerance (within ±2° required), or failure to apply the specified tightening torque (typically 8-10Nm), resulting in an incorrect sensor measurement reference.
  • 4Extreme temperature environments or poor ESP module heat dissipation: Prolonged driving in high temperatures or interference from nearby heat sources causes the internal temperature sensor to trigger a protective fault.
  • 5History of vehicle collision or severe jolting: Damages the internal micro-mechanical structure of the MEMS sensor, or causes terminal back-out or oxidation inside wiring harness connector C2J (or corresponding model-specific connector).
What To Do
  • 1
    Safety Preparation: For E5 battery electric vehicle models, strictly follow high-voltage safety procedures. Disconnect the power battery high-voltage service disconnect and the 12V battery negative terminal. Wait at least 3 minutes for the system to fully discharge.
  • 2
    Initial visual inspection: Inspect the ESP hydraulic modulator assembly (located on the left side of the engine or front compartment) for physical damage or leaks. Check the mounting bracket for deformation. Inspect the wiring harness connector for oxidation, water ingress, or backed-out pins.
  • 3
    Circuit electrical inspection: Use a multimeter to measure the voltage at the ESP module connector power supply terminals (constant B+ must be 12 ± 0.5 V; ignition IG1 must be >11 V during startup). Ground resistance must be <1 Ω. Measure the terminal resistance between CAN-H and CAN-L; it must be 60 ± 6 Ω. Verify the circuit has no short to ground or short to power.
  • 4
    Data stream and freeze frame analysis: Connect the VDS diagnostic tool and read the ambient temperature and vehicle attitude data from the fault freeze frame. Check the real-time data stream for "lateral acceleration" and "yaw rate". With the vehicle stationary on a level surface, these values must be 0±0.5 m/s² and 0±2°/s. If the display shows -40, +40, or a fixed value, this confirms an internal sensor fault.
  • 5
    Installation reference verification: Use a spirit level to check the level of the ESP module mounting surface against the vehicle longitudinal and lateral axes, keeping the installation error within ±2°; use a torque wrench to retighten the mounting bolts to the standard torque (usually 8-10Nm).
  • 6
    Temperature and environment check: Verify if the ambient temperature during the fault was outside the -40°C to +85°C range. Inspect the area around the ESP module for new heat sources causing interference (such as aftermarket modifications).
  • 7
    Component replacement: Upon confirming an internal sensor fault, replace the entire ESP hydraulic modulator assembly with ECU (Note: this sensor is an integrated design; do not replace it separately). Use genuine parts (such as the BYD-3535010 series; confirm the exact part based on the vehicle model year).
  • 8
    System calibration: After replacement, use VDS to perform 'Yaw Rate Sensor Calibration' and 'G-Sensor Calibration'. Some E5 models require 'Longitudinal Acceleration Sensor Learning'.
  • 9
    Function verification and road test: Clear all fault codes and restore the high-voltage system connection. Conduct a road test. At a vehicle speed >20km/h, perform an S-shaped lane change or emergency lane change test. Confirm the ESP function operates normally and C019604 does not recur. Verify the relevant warning lights turn off.
Real-World Cases
BYD DTC AI Analysis

BYD Song Pro ABS wheel speed sensor signal abnormality (C0035/C3004)

✓
**Symptoms:** ABS and ESP warning lights suddenly lit up while driving, with a tyre pressure monitoring alert. Some owners report a slight chassis noise during low-speed turns that disappears above 40 km/h. **Diagnosis:** 1. Scanner showed C0035 (right front wheel speed sensor power supply fault) and C3004 (front wheel ABS speed signal abnormal). 2. Right front tyre pressure read 0.3 bar below specification. 3. Raised the vehicle and found the right front wheel speed sensor packed with iron filings inside the hub, probe covered in metal debris. 4. Resistance check: normal is 1.2–1.8 kΩ, faulty sensor measured 0.8 kΩ (internal short developing). **Fix:** - Cleaned iron filings and grease from the sensor probe and tone ring. - Adjusted sensor-to-tone-ring gap to 0.3–0.8 mm. - Replaced right front wheel speed sensor (PN: BYD-3630100). - Cleared codes and test drove; ABS function normal.
Original source ↗
BYD DTC AI Analysis

BYD Tang DM Steering Angle Sensor Failure (C0051/C0196)

✓
**Symptoms:** After starting the vehicle, the steering system warning light stays on and the instrument cluster displays "Check Steering System". The owner reported abnormal self-centering force from the steering wheel, non-functional lane keep assist at highway speeds, and inability to set cruise control. **Diagnosis:** 1. Connected the VDS scan tool and retrieved steering system DTCs: C0051 (Steering Wheel Position Sensor - Signal B Malfunction) and U0126 (Lost Communication With Steering Angle Sensor Module). 2. Inspected the wiring harness connector beneath the steering column and found green corrosion inside (vehicle had water exposure). 3. Removed the Steering Angle Sensor (SAS module). Supply voltage measured 12V (normal), but CAN-H to CAN-L resistance was 78Ω (normal: 60Ω). 4. Internal circuit board water damage caused signal drift. **Resolution:** - Cleaned the wiring harness connector contacts and applied conductive grease for waterproofing. - Replaced the Steering Angle Sensor assembly (requires dealer zero-point calibration, cost approximately 680 yuan). - Performed the 'Steering Angle Learning' procedure using the scan tool: steer full left, hold 3 seconds → center → steer full right, hold 3 seconds → center. - Fault resolved. Lane keep assist and cruise control functions restored.
Original source ↗
BYD DTC AI Analysis

BYD Qin Pro ESP communication fault (C1414/U-category fault)

✓
**Symptoms:** Vehicle suddenly entered Limp Mode during normal driving, speed limited to 40 km/h. Dashboard showed "Check ESP System" and "Check HHC System". Restarting did not clear the fault; hard acceleration had no response. **Diagnosis:** 1. Scanned all DTCs: multiple C-series codes present — C1414 (Incorrect Module Design Level), C0089 (TCS Disable Switch Fault). 2. Inspected ABS/ESP control unit connector: found pin 14 (CAN-L) retracted, causing intermittent communication loss. 3. Measured ESP module supply voltage: 11.8 V at ignition ON (normal), but dropped to 9.2 V during cranking (battery aged). 4. Network communication faults also present, including U0121 (Lost Communication With ABS Control Module). **Resolution:** - Repaired the ESP control unit connector pin to restore reliable CAN bus connection. - Replaced the aged battery (original unit over 3 years old, insufficient cold cranking amps). - Flashed ESP control unit software to V2.3.1. - Cleared all DTCs and road-tested; Limp Mode cleared.
Original source ↗
Other Atto 3 Fault Codes
P0AA6Hybrid Battery Voltage System Isolation FaultB1108For 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.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.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.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.
Common problems reported for Atto 3 →Atto 3 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.