AU
B1654-00

DTC B1654-00 indicates a communication interruption or abnormal signal between the airbag control unit (SRS ECU) and the left front impact sensor — Seal U

Safety System

DTC B1654-00 indicates a communication interruption or abnormal signal between the airbag control unit (SRS ECU) and the left front impact sensor.

This sensor typically mounts inside the left front fender or on the longitudinal beam.

It uses a two-wire communication circuit (signal wire and ground wire) and contains a piezoelectric or MEMS accelerometer with a normal resistance of approximately 2-3 kΩ.

The ECU sets this DTC if it cannot detect the sensor feedback signal during a self-test or drive cycle, if the resistance falls outside the calibrated range (open or short circuit), or if communication verification fails.

This fault disables the left front collision detection zone.

During a collision, it may prevent accurate airbag deployment or cause unintended deployment, making it a safety-critical fault.

4
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Loose connector, backed-out pins, or oxidation: Sensor plug latch failure, terminal corrosion, or water ingress causes excessive contact resistance. These are the most common causes of intermittent faults.
  • 2Wiring harness open circuit or damage: Sharp sheet metal edges cut the wiring harness after left front fender repairs or collisions, or vibration breaks the wires during long-term use.
  • 3Internal sensor body fault: Aging piezoelectric element, or moisture causing a short or open in the internal circuit, preventing generation of a correct acceleration signal.
  • 4Mounting bracket deformation: Improper alignment of the sensor bracket after accident repairs causes sensor mounting angle deviation or poor connector contact.
  • 5SRS ECU terminal fault: Poor contact or enlarged pin holes at ECU-side G36 connector terminals 33/34 (e.g., Qin model), causing abnormal signal acquisition.
What To Do
  • 1
    Safety Preparation: Power down the vehicle, disconnect the negative battery terminal, and wait at least 90 seconds to prevent accidental airbag deployment.
  • 2
    Fault confirmation: Connect the BYD dedicated diagnostic tool (such as X-431 or ED400), read and record the DTC, and confirm B1654-00 is a current fault, not a history fault.
  • 3
    Visual inspection: Check the left front crash sensor connector (located near the left front fender liner or headlamp bracket) for proper seating, obvious damage, or signs of water ingress.
  • 4
    Circuit continuity test: Disconnect the ECU and sensor connectors. Measure the resistance between ECU terminal G36-33 and sensor terminal C35-2 (L/W wire), and between G36-34 and C35-1 (Br/W wire). Resistance must be less than 1Ω. If resistance is infinite, trace the wiring harness to find the open circuit.
  • 5
    Insulation test: Measure the resistance between the above wiring harness and body ground. The resistance must be greater than 10 MΩ to rule out a short to ground.
  • 6
    Sensor body inspection: Measure the resistance between the two sensor terminals. Normal resistance is 2-3 kΩ (refer to the vehicle repair manual for specific values). If out of range, replace the sensor.
  • 7
    Installation check: Confirm the sensor mounting bracket is not deformed, the sensor fits tightly against the bracket, and the arrow points in the required installation direction (usually toward the front of the vehicle).
  • 8
    Replacement verification: If the above checks are normal, swap the left front and right front sensors and observe if the fault code transfers to confirm an internal sensor fault.
  • 9
    Repair and replacement: Repair harness damage (soldering + heat-shrink tubing), replace damaged sensors or connectors, and use genuine parts.
  • 10
    System reset: Reconnect all components, turn on the power, and use the diagnostic tool to clear the fault codes. Perform an SRS system self-check (ignition switch ON; the indicator light should turn off). Finally, perform a road test to verify.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Poor connection at BYD S6 left front impact sensor connector

✓
The SRS warning light on the instrument cluster illuminated intermittently. The scan tool retrieved DTC B1654-00. Inspection found the locking tab of the collision sensor connector inside the left front fender was loose, with minor oxidation on the terminals. Wiring harness continuity and sensor resistance tested normal. Repair: cleaned the terminals with electronic cleaner, repaired the locking tab, applied conductive grease and reconnected the connector. Cleared the fault code; issue resolved.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin: wiring harness open circuit after accident repair

✓
After left front accident repair, the SRS light stayed on with DTC B1654-00. The sensor connector was good, but the L/W wire (G36-33 to C35-2) had infinite resistance between ECU and sensor. Disassembly found the harness at the inner fender liner cut through by a sharp sheet metal edge. Repair: Cut open the harness sheath, soldered the broken wire, insulated with double-layer heat shrink tubing, rerouted the harness away from sharp edges, and replaced the damaged sensor. Fault cleared.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Surui: Missed connector during accident repair

✓
After front bumper collision repair, the dashboard displayed an airbag warning. Read DTC B1654-00. Inspection found the left front crash sensor connector completely unplugged (the mechanic forgot to connect it). Reconnected the plug and cleared the code. After driving for a while, the fault returned. Further inspection revealed the sensor mounting bracket was deformed in the accident, preventing the sensor from seating properly and putting the connector under tension, causing poor contact. Repair: corrected the bracket flatness, replaced the sensor with a new one, ensured the connector lock clicked fully into place, and secured the wiring harness clip.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Internal piezoelectric element failure in BYD S6 sensor

✓
Vehicle had no collision history. The SRS warning light suddenly illuminated and DTC B1654-00 would not clear. Wiring harness continuity was normal; connectors showed no abnormalities; supply voltage measured 12V (normal). Swapped the left and right front sensors — the fault code changed to B165D-00 (right front sensor fault), confirming an internal failure of the original left front sensor. Disassembly revealed the internal piezoelectric ceramic plate had desoldered. Replaced the OEM left front impact sensor, cleared fault codes, and performed static and dynamic road tests. System 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. Sources: [1]