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B162C1B

DTC B162C1B is a BYD BMS (Battery Management System) fault code — Atto 8

Safety System

DTC B162C1B is a BYD BMS (Battery Management System) fault code.

It indicates abnormal communication between a specific Battery Information Collector (BIC) inside the battery pack and the main BMS, or excessive resistance in the sampling circuit.

Specifically, "B16" designates the BMS subsystem, "2C" identifies a communication or sampling fault in a specific BIC module, and "1B" is the subtype code indicating excessive resistance, an open circuit, or poor contact in that BIC module's CAN communication circuit.

This failure prevents the system from uploading voltage and temperature data for that battery cell group, affecting battery balancing management, SOC calculation, and the high-voltage interlock function.

In severe cases, the fault may prevent the vehicle from enabling the high-voltage system or cause a loss of drive power while driving.

5
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1BIC module connector loose, oxidized, or pins backed out, causing poor contact in the CAN communication line.
  • 2Wear, open circuit, or short circuit in the BIC sampling harness inside the battery pack, especially at the retaining clips.
  • 3BIC sampling board internal circuit fault (e.g., burnt balancing MOSFET or NTC resistor cold solder joint)
  • 4Water ingress or corrosion in the communication wiring harness connector between the BMS main control board and the BIC
  • 5Unstable voltage or poor ground connection of the low-voltage iron battery (12V) causes abnormal BIC power supply.
What To Do
  • 1
    Use the BYD dedicated diagnostic tool (ED400 or X-431) to read complete fault codes and freeze frame data, and confirm which specific BIC module (e.g., BIC1, BIC5) is reporting the fault.
  • 2
    Read the BMS data stream and check the corresponding BIC cell voltage and temperature for abnormal readings (such as -40℃ or 0V).
  • 3
    Inspect the traction battery pack exterior. After confirming no collision deformation, disconnect the high-voltage service disconnect and wait 5 minutes for high-voltage discharge.
  • 4
    Remove the battery pack upper cover, locate the corresponding BIC module, and check the connector for looseness. Measure the supply voltage at the connector (should be approximately 12V) and the CAN line voltages (CAN-H approximately 2.5-3.5V, CAN-L approximately 1.5-2.5V).
  • 5
    Measure the BIC module termination resistance (approximately 60Ω; high resistance indicates an open circuit or poor contact).
  • 6
    Check the BIC harness assembly routing and inspect for harness wear caused by rubbing against metal clips or brackets.
  • 7
    If the wiring harness is normal, replace the faulty BIC sampling board, reflash the BMS software, and perform battery balancing calibration.
  • 8
    Reinstall the battery pack, clear the fault code, perform a high-voltage power-on test, and road test the vehicle to confirm the fault is resolved.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin BMS communication fault (U20B000-BIC1 CAN communication timeout)

✓
BYD Qin DM. The instrument cluster displayed "Power System Fault", the vehicle could not drive in EV mode, and the warning lamp illuminated. The scan tool retrieved U20B000 (BIC1 CAN communication timeout). This code and B162C1B both belong to the BIC communication fault category. Diagnosis: 1. Connected the scan tool and read BMS fault codes; revealed abnormal BIC1 communication. 2. Opened the high-voltage battery pack and inspected the BIC1 sampling board CAN wiring harness. 3. Found the BIC1 module connector loose, with poor contact on the CAN-H and CAN-L signal wires. 4. The BIC1 supply voltage measured normal at 12 V, but the communication waveform was abnormal. Repair: Re-seated the BIC1 sampling board connector, used the special tool to secure the locking clip, and cleared the fault codes. This resolved the fault. Recommendation: Replace the BIC mounting bracket to prevent future loosening.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Tang battery sampling issue (P1A2900 - temperature sampling fault)

✓
BYD Tang DM experienced sudden power limitation while driving, with the dashboard displaying "Battery System Abnormal". Read DTC P1A2900 (Temperature Sampling and Equalisation Circuit Fault), indicating a BMS sampling fault. Diagnosis: 1. Connected an ED400 diagnostic tool and accessed BMS live data; cell string 5 temperature read -40°C (clearly abnormal). 2. Opened the battery pack and inspected the BIC5 sampling board; found a cold solder joint on the temperature sampling NTC resistor. 3. Inspected the wiring harness between the BIC and BMS main board; found oxidation on the cell string 5 sampling line connector. Repair: Re-soldered the NTC resistor, cleaned the sampling connector and applied conductive paste, and replaced the BIC5 sampling board. Fault cleared.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Song Pro EV BIC Balance Fault (P1A2A00)

✓
BYD Song Pro EV exhibited fluctuating charging power and erratic SOC readings during fast charging. Retrieved DTC P1A2A00 (Cell Balancing Circuit Fault). Diagnosis: 1. Read BMS fault codes that indicated a balancing circuit anomaly; 2. Checked cell voltage live data and found the 8th cell voltage deviation exceeded 500 mV; 3. Inspected the BIC8 balancing circuit and found the balancing MOSFET burnt out; 4. Traced the root cause to a previous over-discharge of that cell, which lowered its voltage; prolonged unbalanced operation then burnt out the balancing circuit. Resolution: Replaced the BIC8 sampling board, performed top-up balancing on the 8th cell, reflashed the BMS software, and limited the charge and discharge current for that cell.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD e5 BMS Power Supply Fault (B1FB2/B1FB3)

✓
BYD e5 taxi would not engage high voltage; the instrument cluster displayed "Check Power System". DTCs B1FB2 (Supply Voltage Too Low) and B1FB3 (Supply Voltage Too High) appeared alternately. Diagnosis: 1. Checked the iron battery voltage and found it fluctuating between 11V–16V; 2. Measured the DC-DC output and found it unstable; 3. Checked the BMS power supply harness and found a loose earth point causing abnormal voltage sampling; 4. Checked the BMS internal power module and found the filter capacitor bulging. Solution: Replaced the DC-DC converter, re-tightened the BMS earth point, and replaced the BMS internal filter capacitor. Fault resolved.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Han EV BIC Communication Fault (U029A)

✓
BYD Han EV. Loss of drive power while driving, dash displayed 'High Voltage System Fault'. Diagnostic scan retrieved U029A (Lost Communication With Hybrid Battery Pack Sensor Module). Diagnosis: 1. Measured CAN lines between BMS and battery pack, termination resistance 60Ω — normal; 2. Sectional testing located an open circuit at one point in the battery pack's internal CAN harness; 3. Opened battery pack and found the BIC harness worn through by a retaining clip, causing intermittent open circuit. Solution: Replaced damaged CAN harness and rerouted it to avoid contact with sharp clips. Fault resolved.
Original source ↗
Other Atto 8 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. Sources: [1]