AU
B163B1A

DTC B163B1A indicates the squib circuit resistance of the front passenger side airbag (typically mounted on the outboard side of the front passenger seat or inside the right front door trim panel) falls below the minimum threshold set by the SRS control module (ACM) (typically below 1 — Seal U

Safety System

DTC B163B1A indicates the squib circuit resistance of the front passenger side airbag (typically mounted on the outboard side of the front passenger seat or inside the right front door trim panel) falls below the minimum threshold set by the SRS control module (ACM) (typically below 1.0-1.5 Ω; normal range is 2.0-3.0 Ω).

This condition indicates a partial or complete short in the squib circuit.

Damaged wiring, water ingress at the connector, or an internal airbag fault can cause this issue.

This fault triggers the safety protection mechanism.

The SRS system disables the airbag circuit to prevent unintended deployment and illuminates the airbag warning light on the instrument cluster.

During a side impact, this airbag may fail to deploy normally, severely compromising occupant safety.

3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Airbag igniter internal short circuit: Aging, moisture ingress, overheating, or manufacturing defects cause an inter-turn short circuit in the front passenger side airbag igniter coil, abnormally reducing the resistance value.
  • 2Wiring harness short circuit: Wear, crushing, overly tight retaining clips, or animal bites damage the 2-core wiring harness connecting the airbag and the ACM (routed through the right front door hinge or seat rail), causing a short circuit between the positive and negative wires.
  • 3Connector water ingress or corrosion: Poor sealing of the right front door wiring harness connector (inside the rubber boot at the door hinge) or the airbag connector under the seat allows water entry after wading or washing the vehicle, causing a short circuit between pins or electrolytic conduction.
  • 4SRS control module (ACM) internal monitoring circuit fault: A faulty ACM internal sampling resistor or monitoring chip misinterprets a normal resistance value as low, while the actual wiring harness and airbag unit are normal.
  • 5Improper repair or modification: Previous repairs connected a resistor with excessively low resistance in parallel within the airbag circuit (e.g., using a resistor below 1Ω instead of an airbag), or installed an aftermarket or repaired airbag with mismatched resistance.
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes to discharge the SRS capacitor to prevent accidental airbag deployment. Wear an anti-static wrist strap.
  • 2
    DTC confirmation: Connect the diagnostic tool, read and record the DTCs. Confirm B163B1A is a current fault (Current DTC) and not a history fault. Check if the airbag resistance value in the data stream shows <1.0Ω.
  • 3
    Airbag unit inspection: Remove the front passenger side airbag (disconnect the connector first). Use a high-precision multimeter to measure the resistance between the two pins on the airbag-side connector. Normal resistance is 2.0-3.0 Ω. If the resistance is <1.0 Ω or close to 0 Ω, replace the airbag assembly.
  • 4
    Harness continuity and insulation test: Measure harness continuity from the ACM to the airbag connector (should be <0.5Ω). Measure insulation resistance between the two wires and to body ground (should be >1MΩ). Specifically inspect the harness inside the door hinge protective sleeve and under the seat for wear or short circuits.
  • 5
    Connector inspection and treatment: Inspect connector pins for deformation, corrosion, verdigris, or signs of water ingress. Clean with electrical contact cleaner. Replace the connector or sealing ring if necessary, and apply insulating silicone grease.
  • 6
    ACM replacement verification: If the wiring harness and airbag are normal, replace the ACM with a known-good unit to confirm if an internal module fault caused a false detection.
  • 7
    System reset and test: After repair, restore all connections, clear the fault codes, perform an SRS system self-diagnosis, and confirm B163B1A changes to Passed. Road test the vehicle on a bumpy road to confirm the fault does not recur.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Right front door hinge wiring harness wore through and shorted, causing low resistance.

✓
Symptoms: The airbag warning light on the dashboard stays on continuously. Scan tool shows DTC B163B1A (current). The vehicle has no collision history, but the right front door recently had body repair. Diagnosis: Disconnected the battery, then removed the passenger side airbag connector. The airbag itself measured 2.3Ω (normal). On the harness side, only 0.2Ω remained between the two wires – a short circuit. Removed and inspected the rubber boot at the right front door hinge. The harness inside had been crushed and damaged during the repair, shorting the positive and negative conductors. Resolution: Repaired the damaged harness (re-insulated and wrapped with tape). Rerouted the harness to prevent rubbing. Cleared the fault code, and the system returned to normal.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Passenger seat airbag connector shorted due to water ingress.

✓
Symptoms: After the vehicle waded through water (up to seat level), the airbag warning light flashed and then stayed on. DTC B163B1A appeared intermittently, with higher frequency in humid weather. Diagnosis: Inspected the airbag connector under the passenger seat. Found the connector seal aged and missing, with visible water stains and green copper corrosion inside. The airbag module itself tested normal, but resistance across the harness wires at the connector was 0.5Ω (short circuit). Water ingress during wading caused a short circuit, and the airbag may have sustained internal damage. Repair: Cleaned the connector pins thoroughly and replaced the seal. Replaced the passenger side airbag (due to potential internal short circuit from water ingress). Re-wrapped and waterproofed the wiring harness. Fault resolved.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Metal debris in the ACM connector caused a false short-circuit fault.

✓
Symptom: After starting the vehicle, the message "Please check SRS system" appears intermittently. DTC B163B1A sets as a current code and returns sporadically after clearing, with no specific pattern. Diagnosis: Measured the passenger side airbag and wiring harness resistance – both 2.1Ω (normal). Inspected the SRS control module connector (under the centre console) and found metal debris inside, likely from a previous repair, causing a short between the B163B circuit pins. Resolution: Thoroughly cleaned the ACM connector interior with precision instrument cleaner, blew out debris with an air gun, verified the pins were not deformed, and reconnected. The fault has not returned.
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]