AU
U043204

DTC U043204 indicates a communication timeout between the IPB (Intelligent Integrated Braking System) control unit and the MMx_TX module (Multi-axis Acceleration Sensor) — Seal 6 EV

Braking System

DTC U043204 indicates a communication timeout between the IPB (Intelligent Integrated Braking System) control unit and the MMx_TX module (Multi-axis Acceleration Sensor).

The MMx module monitors the vehicle’s lateral and longitudinal acceleration, providing critical dynamic data for ESP, Automatic Emergency Braking (AEB), Electronic Brakeforce Distribution (EBD), and the brake energy recovery system.

The IPB main control unit triggers this fault if it fails to receive valid acceleration data within the specified communication cycle (usually 200 ms), or if the received data frame contains a checksum error or abnormal length.

The system enters a safety fallback mode, limiting or disabling advanced functions such as ESP and AEB.

The vehicle usually retains basic hydraulic braking, allowing cautious driving to a repair facility.

5
Cases Logged
5
Causes
Likely Causes — Seal 6 EV
  • 1Multi-axis acceleration sensor (MMx) power supply circuit fault (5V reference voltage abnormal or missing) or poor ground connection, preventing normal sensor initialization or continuous operation.
  • 2Physical damage, open circuits, or short circuits in the CAN bus communication lines; or backed-out pins, oxidation, or corrosion from water ingress in key intermediate connectors (e.g., KJG05, BJA01) resulting in excessive contact resistance.
  • 3Multi-axis acceleration sensor damaged (internal MEMS chip failure, cold solder joint, moisture ingress due to seal failure, or performance degradation from physical impact)
  • 4Internal CAN transceiver circuit fault in the IPB integrated brake control unit, software communication protocol mismatch, or damaged main control chip communication port.
  • 5Vehicle wading, cabin water ingress (e.g., leaking from a blocked sunroof drain hose), or high-humidity environments cause corrosion of the sensor connector and wiring harness, resulting in intermittent poor contact.
What To Do
  • 1
    Use the BYD dedicated diagnostic tool (VDS1000/DiLink) to read all fault codes and freeze frame data. Verify if U043204 is a current fault and check associated fault codes (e.g., U012187, U043208, C003500) to assist in fault isolation.
  • 2
    Visually inspect the multi-axis acceleration sensor (typically located under the centre console, at the base of the centre armrest, or under the front seats) for proper mounting, external damage, and secure connector engagement. Verify there are no signs of physical impact.
  • 3
    Measure the sensor supply voltage (ignition ON, 5V±0.25V) and ground resistance (<0.5Ω). Confirm the power supply is stable without fluctuation.
  • 4
    Check the CAN bus physical layer: Measure CAN-H (2.5-2.7 V to ground) and CAN-L (2.3-2.5 V to ground) voltages, and the bus termination resistance (power off, approximately 60 Ω). Confirm no short or open circuits.
  • 5
    Carefully inspect the intermediate connector (especially terminal KJG05-18 and related pins) for backed-out pins, oxidation, or water ingress. Disassemble the connector if necessary, clean with electrical contact cleaner, blow dry, and apply conductive grease for protection.
  • 6
    Measure wiring harness continuity between the sensor and the IPB control unit (resistance less than 1 Ω) and insulation (resistance to ground greater than 10 MΩ). Check for intermittent short circuits or shorts to ground.
  • 7
    If all circuit measurements are normal, replace the multi-axis acceleration sensor assembly. Use the diagnostic tool to perform the sensor zero-point calibration and initialization procedure (Enter IPB system → Special Functions → Sensor Calibration / G-Sensor Calibration).
  • 8
    Clear the fault code and perform a road test (including straight-line driving, turning, hard acceleration, and hard braking). Confirm the ESP and AEB functions operate normally. Read the data stream using the diagnostic tool to confirm the acceleration value is normal (close to 0 m/s² when stationary) and verify the fault code does not recur.
Real-World Cases
BYD DTC AI Analysis

Song Pro multi-axis acceleration sensor connector oxidised, pins backed out

✓
While driving normally, the instrument panel suddenly displayed "Check ESP System" and "Check SRS System", with the ESP and airbag warning lights remaining on. The scan tool read DTCs U043204 and U012187 (lost communication with yaw rate sensor). Inspection revealed water ingress. Pin 18 of the multi-axis acceleration sensor connector (KJG05), located beneath the centre console, was oxidised and slightly backed out. Cleaned the terminals, repaired the backed-out pin, applied conductive grease, and recalibrated the sensor. Fault cleared.
Original source ↗
BYD DTC AI Analysis

Han EV Intermittent Multi-Axis Accelerometer Signal Abnormality

✓
Vehicle started normally from cold. After driving 7–10 km, the ESP warning light and automatic emergency braking limited warning illuminated. Cleared after restart. Retrieved DTCs U043204 and C003500 (acceleration sensor signal abnormal). Data stream showed abnormal lateral and longitudinal acceleration sensor values (reading -0.8 m/s² when stationary; normal should be near 0). Found the sensor connector loose with slight internal damage. Replaced the multi-axis acceleration sensor assembly, performed sensor calibration and steering wheel angle calibration. Fault fully resolved.
Original source ↗
BYD DTC AI Analysis

Tang DM airbag control module communication fault with U043204

✓
While driving, the vehicle suddenly displayed predictive collision warning and pedestrian detection system faults; EV mode unavailable. Read DTCs U043204, P1AC000 (airbag ECU collision warning), and U014000 (lost communication with BCM). Inspection found sunroof drain tube blocked, letting water into the cabin and soak the KJG05 connector, causing intermittent open circuit in the multi-axis acceleration sensor signal line. Cleaned the connector, cleared the drain tube, dried the wiring harness and waterproofed. Fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD Qin Pro multi-axis accelerometer wiring harness chafed and shorted

✓
After driving over rough roads, the ESP and airbag warning lights illuminated and ESP failed at high speed. Retrieved DTCs U043204 and B190014 (sensor signal short to ground). The multi-axis acceleration sensor signal line showed 0Ω resistance to ground. Traced the wiring harness chafing through at the firewall grommet, causing the short. The sensor was also damaged. Repaired the harness, rerouted the wiring to prevent further chafing, replaced the sensor and performed the initialization procedure. Fault resolved.
Original source ↗
BYD DTC AI Analysis

Aftermarket audio installation caused CAN bus interference on Song MAX

✓
Aftermarket audio installation caused intermittent ESP and airbag fault warnings on the instrument cluster, occurring more frequently when the subwoofer was active. Codes U043204 (history) and U0021 (CAN bus open circuit) were logged. The audio power cable was running parallel to the main wiring harness, creating electromagnetic interference, and the amplifier ground point was improper, causing ground return interference. Rerouting the audio wiring (maintaining 15 cm or more separation from the main harness), relocating the ground connection to the designated body ground point, and installing ferrite cores on the sensor CAN lines resolved the issue. The faults have not returned.
Original source ↗
Other Seal 6 EV 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.B1737DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.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 Seal 6 EV →Seal 6 EV 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.