AU
C055164

DTC C055164 indicates the IPB (Integrated Power Brake) detects a fault in the Longitudinal Acceleration Sensor signal circuit — Seal U

Braking System

DTC C055164 indicates the IPB (Integrated Power Brake) detects a fault in the Longitudinal Acceleration Sensor signal circuit.

This sensor monitors longitudinal acceleration (braking deceleration/driving acceleration) and provides key vehicle dynamic parameters to the ESC (Electronic Stability Control), ABS (Anti-lock Braking System), AEB (Autonomous Emergency Braking), and energy recovery systems.

When the fault triggers, the longitudinal acceleration signal status bit the IPB receives via CAN message 0x223 indicates an error (such as invalid signal, checksum error, or timeout), preventing the system from accurately determining the vehicle motion state.

In severe cases, ESC, ABS, and AEB functions may enter a degraded mode or fail completely.

The instrument cluster illuminates multiple brake system warning lamps, and extreme conditions compromise vehicle braking safety and stability control.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Loose inertia sensor wiring harness connector, backed-out pins, or corroded terminals: Poor contact at the IPB assembly or independent longitudinal acceleration sensor connector (depending on vehicle configuration), especially after driving through water, driving over rough roads, or an accident.
  • 2Longitudinal acceleration sensor hardware fault: Internal MEMS element damage, zero-point drift, or abnormal signal output causes the output voltage to exceed the IPB recognition range (typically 0.5-4.5V corresponding to ±1.5g).
  • 3IPB internal signal acquisition circuit fault: The 5V reference power supply to the sensor inside the IPB module has a short or open circuit, or a damaged signal acquisition ADC circuit fails to correctly process the sensor analog signal.
  • 4Abnormal sensor mounting position or physical damage: Failure to recalibrate the sensor after a vehicle collision or a deformed mounting bracket causing sensor mounting angle deviation, or a severe impact damaging the sensor's internal vibrating beam.
  • 5CAN network communication interference: Abnormal network impedance, electromagnetic interference, or a terminal resistor fault between the IPB and the sensor (if the sensor communicates via CAN bus rather than a hardwired connection) causes 0x223 message loss or checksum errors.
What To Do
  • 1
    Step 1: DTC freeze frame analysis and preliminary inspection: Use the VDS2000 or DMS diagnostic tool to read the DTC freeze frame. Verify parameters at the time of the fault, including vehicle speed, longitudinal acceleration, and yaw rate. Check the vehicle history for collisions, water ingress, or modifications. Visually inspect the IPB assembly and wiring harness for damage.
  • 2
    Step 2: Power supply and ground circuit inspection: Disconnect the IPB connector (or independent sensor connector). Check the sensor supply voltage (standard: 5V±0.25V). Check the ground wire resistance (must be less than 1Ω). Confirm the reference voltage is stable without fluctuation. If the voltage is abnormal, repair the wiring harness or replace the IPB.
  • 3
    Step 3: Signal circuit continuity and insulation test: Use a multimeter to measure continuity between the longitudinal acceleration sensor signal wire (usually marked LA-G or LongAccel) and the IPB. Resistance must be less than 1 Ω. Measure the insulation resistance from the signal wire to the power supply and to ground. Resistance must be greater than 10 MΩ. Inspect the connector terminals for terminal spread or backed-out pins.
  • 4
    Step 4: Sensor signal waveform verification: Connect an oscilloscope and monitor the sensor output signal waveform while the vehicle is stationary and during acceleration/braking. The normal signal is a stable DC voltage (approximately 2.5V when stationary). Voltage increases during hard acceleration and decreases during hard deceleration. If the signal spikes, drops out, or exceeds the range, replace the sensor or IPB assembly.
  • 5
    Step 5: IPB communication and software check: Verify the IPB CAN-H (2.5-3.5 V) and CAN-L (1.5-2.5 V) waveforms are normal; check the IPB software version and flash the software if required by a technical bulletin; check for related combination fault codes (e.g., C055100-C055500 series).
  • 6
    Step 6: Sensor calibration and system verification: After rectifying the fault, use the diagnostic tool to perform Longitudinal Acceleration Sensor Calibration. Clear the fault codes and perform a road test (including straight-line acceleration, emergency braking, and cornering braking) to confirm the fault code does not return and the ESC function operates normally.
Real-World Cases
BYD DTC AI Analysis

Signal Drift in Song Plus DM-i Due to IPB Connector Corrosion After Water Wading

✓
A 2021 Song PLUS DM-i showed "Brake System Fault" after driving through heavy rain and flood water. Scanner read DTC C055164. The IPB sits on the left side of the engine bay; its wiring harness connector seal had degraded, letting water in that oxidised the longitudinal acceleration signal terminal and created contact resistance (reference voltage dropped from 2.3V to 1.8V). Cleaned the connector, applied conductive paste, and replaced the waterproof seal. Fault resolved.
BYD DTC AI Analysis

Seal 6 DM-i fault after accident repair: calibration not performed

✓
Following front-end collision repairs that replaced the front bumper and wiring harness, the instrument cluster continuously displayed C055164. Diagnosis revealed the IPB had been replaced but technicians had not performed the sensor zero-point calibration. Ran the 'Longitudinal Acceleration Sensor Calibration' procedure using VDS with the vehicle stationary and level. Cleared the fault code after calibration; ESC function returned to normal.
BYD DTC AI Analysis

Faulty 5V power module inside IPB caused abnormal signals

✓
A Qin PLUS DM-i with 80,000 km logged DTC C055164. The IPB’s 5V reference supply to the longitudinal acceleration sensor was jumping randomly between 3–5 V. An external stable 5 V supply restored normal sensor signal, isolating the fault to the IPB’s internal power management chip. Replaced the IPB assembly (part number possibly 3568110-XX) and performed online matching. Issue resolved.
BYD DTC AI Analysis

Wiring harness chafing caused intermittent open circuit in the signal circuit

✓
Vehicle intermittently logs C055164 over speed bumps or rough roads; normal on flat roads. Inspection found the IPB wiring harness chafing against body sheet metal at the firewall penetration. Long-term wear damaged the insulation on the longitudinal acceleration signal wire, causing momentary short to ground over bumps. Repaired the wiring, rerouted and secured the harness, and added anti-abrasion sleeving. Fault has not returned.
Other Seal U 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.