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B169F

In BYD new energy vehicles, DTC B169F indicates an ESP (Electronic Stability Program) control unit communication fault, not an SRS airbag fault (early documentation may contain classification errors) — Seal U

Safety System

In BYD new energy vehicles, DTC B169F indicates an ESP (Electronic Stability Program) control unit communication fault, not an SRS airbag fault (early documentation may contain classification errors).

This fault code indicates the powertrain CAN or chassis CAN bus fails to receive a valid data frame from the ESP control module (integrated into the vehicle stability system, typically located on the left side of the engine compartment or inside the left front wheel arch), or the received signal fails verification.

This disables the Electronic Stability Program, traction control, anti-lock braking system (ABS), and advanced driver assistance functions relying on ESP signals (such as adaptive cruise control and lane keeping).

Root causes include a physical-layer CAN bus communication interruption, abnormal terminating resistance, a control unit power supply/ground fault, or a software version mismatch.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Poor contact, oxidation, or water ingress at the ESP control module wiring harness connector (the module mounting location exposes it to mud splash and car wash water intrusion, causing terminal corrosion)
  • 2CAN bus circuit fault (CAN-H or CAN-L short or open circuit, disrupted twisted-pair spacing, or terminating resistance deviation from the standard value of 60 Ω)
  • 3ESP control unit power supply or ground fault (blown fuse, poor relay contact, loose ground point causing voltage drop)
  • 4Control unit internal hardware damage (CAN transceiver chip failure due to overvoltage, short circuit, or electrostatic breakdown interrupts communication)
  • 5Software version mismatch or flashing failure (interrupted OTA upgrade, or ESP module software version incompatible with VCU/BCM)
What To Do
  • 1
    Use BYD dedicated diagnostic tool VDS2000/VDS3000 to read the complete fault codes and freeze frame data. Check for accompanying related fault codes such as U010104 (Lost communication with ESP) or U030198 (Software version mismatch).
  • 2
    Check the power supply voltage (standard 12V±0.5V) and ground resistance (< 1Ω) of the ESP control module (part number typically BYD-3636100 series) to confirm the power and ground circuits are normal.
  • 3
    Measure CAN bus physical layer parameters: CAN-H to ground voltage 2.5-2.7V, CAN-L to ground voltage 2.3-2.5V, and differential voltage approximately 0.2V. Disconnect power and measure terminal resistance. Resistance must be 55-65Ω (if abnormal, check the 120Ω terminating resistor for damage or the wiring for short circuits).
  • 4
    Check the ESP module wiring harness connector (especially at the mounting location inside the left front wheel arch) for proper sealing. Inspect for water stains, verdigris, or loose pins. Clean with precision electrical contact cleaner and apply conductive paste or waterproof silicone grease.
  • 5
    Inspect along the CAN wiring harness routing for crushing, damage, or insulation wear caused by rubbing against metal body components. Focus on accident repair areas and wiring harness retaining clips.
  • 6
    Perform software diagnostics: Check if the ESP control unit software version matches the vehicle configuration. Attempt to reflash the latest software version (ensure vehicle battery level >50% and a stable diagnostic tool connection).
  • 7
    If all the above checks are normal, replace the ESP control module assembly. After replacement, perform the steering angle sensor calibration (steering wheel centering and left/right limit position learning), wheel speed sensor signal check, and ESP system self-learning procedure.
Real-World Cases
BYD DTC AI Analysis

Song Pro DM: Intermittent ESP warning while driving

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Symptoms: The ESP, ABS and tyre pressure warning lights suddenly illuminated on the dash while driving, displaying 'Check ESP System'. The fault occasionally cleared after cycling the ignition, but returned during subsequent driving. Diagnosis: VDS retrieved DTCs B169F (Lost Communication with ESP) and U010104. ESP module power supply and earth: normal. CAN line voltage: normal. Intermittent contact at pin 14 (CAN-H) of the module connector; fault reproduced when wiggling the wiring harness. Resolution: Replaced the ESP control module connector assembly (BYD-3636100). Re-crimped the pins and applied conductive grease. Measured termination resistance at 60Ω – normal. Road test confirmed the fault was resolved.
Original source ↗
BYD DTC AI Analysis

Qin Plus DM-i multiple system warnings on cold start

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Symptoms: During cold starts in winter, the engine, ESP, ABS and airbag lights illuminate simultaneously and may extinguish on their own after 5–10 minutes of driving. Frequency increases after rain or washing the vehicle. Diagnosis: Scanned DTCs B169F (ESP communication fault) and B1600 (airbag control unit communication fault, intermittent). Inspection revealed the ESP module, located above the left front wheel, is prone to water ingress. Disassembled the connector and found internal water staining and green copper corrosion. CAN line resistance fluctuated between 55–75 Ω. Resolution: Cleaned and blow-dried the connector, replaced the deteriorated seal (BYD-3636980), applied waterproof silicone grease and re-wrapped the wiring harness. Advised against high-pressure washing of the engine bay.
Original source ↗
BYD DTC AI Analysis

Tang DM: No communication with ESP after accident repair

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Symptoms: After the front collision repair, the vehicle displayed 'ESP malfunction' on startup and the steering was heavy (EPS relies on the ESP steering angle signal). Diagnosis: We scanned with VDS and retrieved codes B169F (invalid ESP signal) and C0035 (left front wheel speed sensor fault, historic). Inspection found a mounting screw had pinched the ESP module wiring harness during the accident repair, damaging the CAN wire insulation and shorting it to ground. Measured CAN-H resistance to ground: 0Ω. Fix: We repaired the damaged CAN wiring harness by insulating with heat-shrink tubing, rerouted the harness, replaced the possibly damaged ESP control module (BYD-3636100-B1), then performed steering angle sensor calibration and wheel speed signal checks after installation.
Original source ↗
BYD DTC AI Analysis

Han EV ESP communication error after OTA update

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Symptoms: After OTA update from V1.2 to V1.3, at startup the next day the ESP warning light stayed on. Adaptive cruise control and lane keeping assist did not work. Diagnosis: VDS read DTCs B169F (Lost Communication With ESP) and U030198 (Software Version Mismatch). The ESP module had software V2.1 but the VCU expected V2.2, suggesting an incomplete OTA flash. A re-flash attempt prompted ‘Communication Timeout’. Solution: Disconnected the battery negative terminal for 5 minutes to reset the CAN network. Used VDS offline mode to force-flash the ESP software to V2.2.1, keeping battery charge above 50%. Cleared fault codes afterward, then performed ESP system self-learning and EPB function check. Intelligent driving assistance functions returned to normal.
Original source ↗
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.