AU
C019604

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

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 — Qin Plus
  • 1Physical damage, aging, or poor internal solder joints of the inertia sensor chip inside the ESP hydraulic control unit (HECU) assembly, causing signal drift or complete loss of output.
  • 2Sensor power supply circuit fault: including unstable constant power (B+) or ignition power (IG1) voltage, or excessive ground circuit resistance (>1Ω), causing the sensor reference voltage (usually 5V) to drift.
  • 3Module installation issue: The angle between the mounting surface and the vehicle horizontal plane exceeds tolerance (±2° required), or failure to tighten the module to the specified torque (typically 8-10Nm) causes an incorrect sensor measurement reference.
  • 4Extreme temperature environments or poor ESP module heat dissipation: Prolonged driving in high-temperature environments or interference from heat sources near the module causes the internal temperature sensor to trigger a protective fault.
  • 5Previous vehicle collision or severe jolting: Damages the internal micromechanical structure of the MEMS sensor, or causes terminal back-out or oxidation inside wiring harness connector C2J (or corresponding vehicle model connector).
What To Do
  • 1
    Safety preparation: For the E5 battery electric model, strictly follow high-voltage safety procedures. Disconnect the power battery high-voltage service disconnect, disconnect the 12V battery negative terminal, and wait at least 3 minutes to fully discharge the system.
  • 2
    Initial visual inspection: Check the exterior of the ESP hydraulic modulator assembly (located on the left side of the engine compartment or front compartment) for physical damage or leaks. Inspect the mounting bracket for deformation. Check the wiring harness connector for oxidation, water ingress, or backed-out pins.
  • 3
    Electrical circuit inspection: Use a multimeter to measure the voltage at the ESP module connector power 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 shorts to ground or power.
  • 4
    Data stream and freeze frame analysis: Connect the VDS diagnostic tool and read the ambient temperature and vehicle attitude data in 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 read 0±0.5 m/s² and 0±2°/s. A reading of -40, +40, or a fixed value confirms an internal sensor fault.
  • 5
    Installation reference verification: Use a spirit level to check the level of the ESP module mounting surface relative to the vehicle longitudinal and lateral axes. Verify the installation error is within ±2°. Use a torque wrench to retighten the mounting bolts to the standard torque (typically 8-10Nm).
  • 6
    Temperature and environment check: Verify if the ambient temperature during the fault was outside the -40°C to +85°C range. Check for new heat sources around the ESP module causing interference (such as aftermarket modifications).
  • 7
    Component replacement: If testing confirms an internal sensor fault, replace the complete ESP hydraulic modulator assembly with ECU (Note: this sensor is integrated and not serviceable separately). Use genuine parts (such as the BYD-3535010 series; verify 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". For some E5 models, perform "Longitudinal Acceleration Sensor Learning".
  • 9
    Function verification and road test: Clear all fault codes and restore the high-voltage system connection. Perform a road test. At vehicle speeds >20 km/h, perform an S-curve or emergency lane change maneuver to confirm the ESP functions normally and C019604 does not recur. Verify the related warning lights are 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 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.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.