AU
B163A

This fault code indicates the Supplemental Restraint System (SRS) detects a 0Ω resistance in the front passenger side airbag firing circuit (typically located in the seat side or B-pillar/curtain) — Seal U

Safety System

This fault code indicates the Supplemental Restraint System (SRS) detects a 0Ω resistance in the front passenger side airbag firing circuit (typically located in the seat side or B-pillar/curtain).

Normal airbag igniter resistance is 1.6-2.4Ω.

A 0Ω resistance indicates a low-impedance short circuit.

Possible causes include a wiring harness short to ground, shorted connector pins, an internal short in the airbag inflator (igniter), or a faulty internal monitoring circuit in the SRS control unit (ACU).

The ECU disables this airbag circuit to prevent accidental deployment.

The airbag will fail to deploy during a side impact, severely compromising occupant protection.

Some early repair data or specific vehicle models define B163A as an anti-theft system communication fault.

Always reference the current vehicle repair manual for actual diagnosis.

4
Cases Logged
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Causes
Likely Causes — Seal U
  • 1Front passenger side airbag wiring harness chafed or insulation damaged, causing short to ground (commonly at seat slide rails, B-pillar trim, or floor harness pass-throughs).
  • 2Water ingress, oxidation, or bent and touching pins at the under-seat airbag connector (usually located on the inner side of the seat track or at the seat base), causing a short circuit.
  • 3Internal short circuit in the airbag gas generator (igniter) causes resistance to drop abnormally to 0 Ω (replace airbag assembly).
  • 4Internal fault in the SRS control module (ACU) driver/monitoring circuit causing a false detection (actual circuit is normal but the module falsely reports a short circuit)
  • 5Wiring harness insulation damaged or fixing screw pierced the wiring harness during vehicle modification (such as installing seat heating, ventilation systems, or full-coverage seat covers).
What To Do
  • 1
    Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment and personal injury.
  • 2
    Fault confirmation: Connect the VDS or X431 diagnostic tool to read DTCs. Confirm B163A is a Current fault, not a History fault. Record the environmental conditions from the freeze frame data.
  • 3
    Visual inspection: Inspect the airbag wiring harness connectors under the front passenger seat, inside the B-pillar trim panel, and at the door sill for looseness, water ingress, corrosion, or obvious physical damage. Focus on the wiring harness sleeve at the seat slide rail.
  • 4
    Isolation diagnosis: Disconnect the front passenger airbag connector (protect the wiring harness side with a shorting clip). Connect a dedicated airbag load simulator (2Ω dummy load) to the SRS ECU side and read the resistance. If the resistance returns to normal, the fault is in the airbag unit or wiring harness. If it remains at 0Ω, the fault is in the wiring harness or ECU.
  • 5
    Harness inspection: Measure the resistance of the two airbag circuit wires to body ground (should be >1 MΩ). Measure continuity between both ends of the harness (should be <1 Ω). Check for a short to ground or short to power. Use an oscilloscope to check for line interference if necessary.
  • 6
    Component inspection: If the wiring harness is normal, use the dedicated airbag tester to measure the airbag inflator resistance (must be 1.6-2.4Ω. 0Ω indicates an internal short circuit; replace the airbag assembly. Never measure directly with a multimeter).
  • 7
    Repair/Replace: Repair the damaged wiring harness (solder and insulate with heat-shrink tubing). Replace damaged connectors (use only OEM waterproof connectors). Replace the airbag module if an internal short circuit exists. Verify all connectors clip into place with an audible click.
  • 8
    System verification: Reconnect the battery, clear the fault code, turn the ignition switch to ON, and check if the airbag warning lamp turns off within the specified time (turning off after 6 seconds normally indicates the system passed the self-check). Perform a road test to confirm.
  • 9
    Final check: Use the diagnostic tool to perform an SRS system self-test and configuration check, confirm B163A does not return, verify related functions operate normally, and complete the repair record.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Tang DM immobiliser system communication fault causing no-start condition

✓
Symptoms: Vehicle failed to start. Start button had no response, dashboard displayed "Check Powertrain" warning, warning light on. DTC B163A was stored (immobiliser authentication failure/communication error). Diagnosis: Connected scan tool, retrieved DTC B163A and multiple network communication fault codes. Checked Body Control Module (BCM) power supply and ground circuits – normal. Inspected wiring between immobiliser coil and BCM, found loose connector. Measured immobiliser coil resistance at 1.2 Ω – normal. Suspected BCM software issue or hardware fault. Resolution: Disconnected, cleaned, and reconnected the harness connector between BCM and immobiliser coil, applied conductive grease. Reset BCM by disconnecting battery negative terminal for 5 minutes. Performed immobiliser system matching/learning with dedicated diagnostic tool. If fault persists, upgrade BCM software or replace BCM module. Note: This B163A code in the original case data relates to the immobiliser system. Depending on model and year, it may differ from airbag fault code definitions.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Song Pro smart key intermittent failure

✓
Symptoms: Smart key intermittently failed to unlock the vehicle. After entering the car, the message “Key Not Detected” appeared when pressing the start button. DTCs B163A and B163B were present simultaneously (weak key signal/authentication failure). Diagnosis: Connected a scan tool and retrieved B163A (immobiliser control unit communication fault). Checked smart key battery voltage (3.0 V, normal). Inspected the wiring between the cabin LF (low frequency) antenna and BCM; found the passenger-side LF antenna connector under the carpet had water ingress and oxidation. Measured the LF antenna inductance and found it was higher than normal (normal approx. 1.2 mH). Resolution: Cleaned and dried the LF antenna connector, then applied waterproof sealant. Replaced the passenger-side LF antenna. Performed key matching programming. Note: In the original case documentation, B163A relates to the immobiliser system. On other models or model years, this DTC may be defined as an airbag fault.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin Plus DM-i won't start after accident repair

✓
Symptoms: After front-end accident repairs, the vehicle wouldn't start. The instrument cluster showed an immobiliser active warning. Stored fault code: B163A (immobiliser internal fault). Diagnosis: Scanned for codes: B163A and multiple U-series communication codes. Inspected the repaired area and found the front compartment harness connector (BCM power) not fully seated. Checked BCM fuses: F2/14 (10A) blown. Measured BCM voltages: ACC power normal, constant B+ unstable. Traced the circuit and found body harness damage from the accident repair, causing an intermittent short circuit. Resolution: Repaired the damaged harness and re-insulated it. Replaced the blown fuse. Reconnected all BCM connectors and confirmed they locked securely. Used a VDS diagnostic tool to reset the immobiliser and match the keys. Note: In this case, B163A relates to the immobiliser system. Depending on model and year, the definition may differ — in some vehicles this code is for the airbag system.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Han EV: Immobiliser matching after BCM replacement

✓
Symptoms: After fitting a new Body Control Module (BCM), the vehicle would not start and the instrument cluster displayed "Check Anti-theft System". Read DTC B163A (Immobiliser Control Unit Not Configured/Communication Interrupted). Diagnosis: Confirmed the replacement BCM part number matched the original. Checked the BCM coding/configuration; the new BCM was missing the VIN and immobiliser configuration data. Inspected the transponder coil connection and found it normal; the key chip functioned correctly. Used a scan tool to read the BCM live data, which showed the immobiliser status as "Inactive". Repair procedure: Connected a BYD-specific diagnostic tool (VDS or Launch X431). Navigated to "Special Functions" → "BCM Configuration" and wrote the vehicle VIN. Performed "Immobiliser System Matching": matched the key, engine ECU, and BCM in sequence. Cleared the fault codes after completing the matching. The vehicle started normally. Note: In the original case materials, B163A relates to the immobiliser system and may differ from current airbag fault code definitions depending on vehicle model and year.
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]