AU
B163C1B

DTC B163C1B indicates the front passenger side airbag igniter circuit resistance exceeds the normal threshold (typically 2 — Seal U

Safety System

DTC B163C1B indicates the front passenger side airbag igniter circuit resistance exceeds the normal threshold (typically 2.0–3.0 Ω).

The system triggers this fault upon detecting resistance > 6 Ω or an open circuit.

This fault falls under the SRS (Supplemental Restraint System) passive safety category, specifically indicating a high-resistance fault in the front passenger seat-mounted side airbag or curtain airbag electrical circuit.

High resistance indicates poor circuit contact, a broken wiring harness, an oxidized connector, or an open airbag igniter.

This condition may prevent proper airbag deployment during a collision, constituting a safety-related functional fault.

4
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Loose or oxidized airbag harness connector under the front passenger seat: Qin PRO series seats feature electric adjustment. Frequent forward and backward movement causes loosening, terminal back-out, or pin oxidation at the yellow airbag connector under the seat (usually located on the inner side of the seat rail), increasing contact resistance.
  • 2Internal open circuit in the clock spring (spiral cable): Although the clock spring under the steering wheel primarily connects the driver-side airbag, some models route the front passenger airbag signal through it. Fatigue fracture of the internal flat cable causes abnormal circuit resistance.
  • 3Airbag igniter internal open circuit: The internal igniter resistance wire in the front passenger side airbag module (integrated into the side of the seat backrest) broke due to aging, or poor production batch welding caused resistance drift.
  • 4Harness wear causing open circuit: Prolonged harness chafing against the seat frame edge or inside the B-pillar trim partially breaks the copper wire, creating a high-resistance state without a complete disconnection.
  • 5SRS control module (ACU) internal sampling circuit fault: A faulty internal A/D converter or voltage divider resistor in the control module causes a false high resistance reading, while the actual external circuit is normal.
What To Do
  • 1
    Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes to discharge residual charge in the system capacitors. Use a multimeter to confirm the SRS system voltage is 0V. Wear an anti-static wrist strap.
  • 2
    Read data stream: Use the BYD VDS2000/VDS3000 diagnostic tool to access the SRS system. Read the freeze frame data for B163C1B. Confirm the current resistance value (usually 10Ω or higher, or displaying 'open circuit') and verify the fault status (current/history).
  • 3
    Visually inspect the seat wiring harness: Remove the front passenger seat (4 retaining bolts, 25Nm torque). Inspect the yellow dedicated connector under the seat (2-pin or 4-pin) for looseness, water ingress, oxidation, or terminal back-out. Test the connector contact pressure using a dedicated probe.
  • 4
    Resistance measurement: Use a dedicated fused airbag test lead (to prevent electrostatic deployment), disconnect the airbag connector, and measure the resistance of the airbag inflator body. The resistance must be 2.0 ± 0.3 Ω. If the resistance is >5 Ω, replace the airbag module. Measure the wiring harness continuity from the seat connector to the SRS control module; the resistance must be <1 Ω.
  • 5
    Check the clock spring (if applicable): Remove the steering wheel and check continuity in the passenger-side circuit of the clock spring. If the circuit is open, replace the clock spring (align the centering marks during installation).
  • 6
    Repair and verification: Clean the oxidized connector using electronic contact cleaner. If necessary, replace the connector or repair the wiring harness (solder and heat-shrink tubing). Restore the connection and clear the fault code. Perform 3 ignition cycle self-checks to confirm the fault code does not recur. Finally, perform an airbag system simulated deployment test (use a dedicated tool in place of the airbag to verify circuit integrity).
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Oxidised seat connector caused intermittent high resistance on Qin Pro DM

✓
A 2019 Qin Pro DM with 32,000 km had an intermittent SRS warning light on the instrument panel. The stored DTC was B163C1B (active). Inspection found green oxide inside the yellow connector under the front passenger seat, and insufficient pin contact pressure. The cause: the vehicle had been driven through water, allowing moisture to seep under the seat. The fix: cleaned the connector with WD-40 Precision Electrical Contact Cleaner, applied conductive grease, and adjusted the terminal spring tension. The fault cleared. A one-week follow-up confirmed no recurrence.
BYD DTC AI AnalysisFrom Chinese market (translated)

Open circuit in passenger-side airbag module internal igniter.

✓
2018 BYD Qin PRO (petrol). Replaced the passenger seat assembly after accident repairs. After installation, logged DTC B163C1B. Measured the new seat airbag resistance: open circuit. Disassembly revealed the airbag igniter pins fractured due to stress during transport. Replaced the seatback side airbag module (PN: K8A-5820400). Remeasured resistance: 2.1 Ω. Cleared the DTC, system normal. Do not drop or stack airbag modules.
BYD DTC AI AnalysisFrom Chinese market (translated)

Worn B-pillar wiring harness caused resistance drift.

✓
A Qin PRO DM with 58,000 km had the passenger side airbag warning light staying on constantly. Diagnosis found the wiring harness between the seat connector and SRS module had worn through its insulation at a corner of the B-pillar trim, the copper core partially broken with only 2-3 strands still connected. Resistance measured 8.5Ω (unstable). Stripped back the harness, cut out the damaged section, and soldered in 0.5mm² high-temperature silicone wire. Reinforced the harness routing to prevent contact with sharp edges. Fault resolved.
BYD DTC AI AnalysisFrom Chinese market (translated)

SRS control module false positive

✓
2019 Qin Pro, no accident history. SRS warning light illuminated suddenly, storing DTC B163C1B. Passenger airbag resistance: 2.0Ω (normal). Wiring harness continuity checked normal. Connectors showed no abnormalities. Suspected internal ACU fault. Upgraded SRS control module software from V1.2 to V1.4; fault persisted. Replaced SRS control module (part no. K8A-3636100), performed online configuration coding, and cleared the fault. Cause: aging of the internal sampling resistor in the control module.
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]