AU
B161C1B

DTC B161C1B indicates the Passenger Front Airbag ignition circuit resistance exceeds the threshold set by the SRS control module (normal range is typically 2 — Qin Plus

Safety System

DTC B161C1B indicates the Passenger Front Airbag ignition circuit resistance exceeds the threshold set by the SRS control module (normal range is typically 2.0-3.0Ω; the module triggers the code upon detecting resistance >3.5Ω or an open circuit).

This active SRS system fault means the passenger front airbag may fail to deploy during a collision, or abnormal signals may force the system into fail-safe mode.

In the BYD diagnostic protocol, the '1B' suffix specifically denotes 'resistance too high/open circuit'.

Poor wiring connections, oxidized connectors, poor clock spring contact, or increased internal airbag module resistance typically cause this condition.

This fault illuminates the instrument panel SRS warning lamp and disables the passenger front airbag.

As a safety-critical fault, it requires immediate repair.

5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1Front passenger airbag wiring harness connector loose, oxidized, or corroded (located on the right side of the dashboard or behind the glove box; front passenger kicks or liquid ingress often cause poor contact)
  • 2Worn internal carbon brush or poor contact in the clock spring (spiral cable) causing increased signal transmission resistance.
  • 3Airbag module internal igniter resistance increased due to aging, or poor internal solder joint.
  • 4Frequent movement or compression breaks internal copper strands or causes intermittent connections in the under-seat or floor wiring harness (especially on models equipped with seat position sensors).
  • 5Improperly installed aftermarket equipment (such as dash cams or ambient lighting) drawing power from the airbag system or splicing into the wiring, causing abnormal circuit resistance.
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (to ensure the SRS capacitor discharges fully). Wear an anti-static wrist strap. Do not use a multimeter in resistance mode to measure directly near the airbag (to prevent accidental deployment).
  • 2
    Visual inspection: Inspect the front passenger airbag module connector (usually located inside the right dashboard trim panel or behind the glove box) for looseness, water ingress, oxidized pins, or backed-out terminals. Clean the connector and apply conductive grease if necessary.
  • 3
    Circuit measurement: Use a high-precision multimeter to measure the front passenger airbag circuit resistance from the SRS control module side (standard value: 2.0-3.0 Ω). Simultaneously measure the insulation resistance to ground (must be >1 MΩ) and check for intermittent open circuits.
  • 4
    Clock spring inspection: Remove the lower steering wheel trim panel, check the clock spring connector connection, and measure continuity across both ends of the clock spring (resistance must remain stable while turning the steering wheel, with fluctuation <0.5Ω).
  • 5
    Component substitution test: If the circuit is normal, perform a substitution test using a known-good front passenger airbag module (Note: Do not measure the resistance of the airbag module itself) to confirm whether the fault transfers.
  • 6
    System reset: After repair, reconnect the battery. Use VDS2000 or a dedicated BYD diagnostic tool to clear the fault code. Execute "SRS System Configuration" and "Sensor Calibration". Perform a collision simulation test (using an airbag test resistor) to verify normal circuit operation.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Oxidation of the passenger airbag connector caused high resistance on the Qin Pro DM

✓
A 2019 BYD Qin Pro DM displayed 'Please Check SRS System' on the dash. DTC B161C1B stored. Removed the glovebox to access the passenger airbag connector behind it. Pins were oxidised and blackened by A/C condensate leakage. Contact resistance measured 5.2 Ω. Cleaned the pins with WD-40 Precision Electrical Cleaner, applied conductive grease, and resistance restored to 2.3 Ω. Cleared the DTC – fault resolved. Check the A/C drain hose for blockages to prevent recurrence.
BYD DTC AI AnalysisFrom Chinese market (translated)

Aftermarket dashcam power tapping caused airbag circuit fault

✓
2018 BYD Qin Pro petrol. Owner installed a dashcam, tapping power from the passenger airbag wiring harness, causing DTC B161C1B. Inspection found aftermarket wiring spliced into the airbag circuit, adding series resistance (about 1.5Ω), bringing total resistance to 4.8Ω. Removed the unauthorised modification, restored factory wiring insulation, cleared fault codes with a diagnostic tool, and ran a system self-test. SRS warning light went out. Fault resolved. Reminded owner never to tap power from the airbag system.
BYD DTC AI AnalysisFrom Chinese market (translated)

Internal wear in the clock spring caused an intermittent fault.

✓
A 2018 Qin Pro DM with 80,000 km developed an intermittent SRS warning light and DTC B161C1B that appeared sporadically. Inspection showed the passenger airbag circuit runs through the clock spring (spiral cable). Disassembly revealed worn carbon brushes inside the clock spring, causing contact resistance to spike at specific steering wheel angles. Replaced the clock spring assembly (part number: BC-5820340). Measured circuit resistance stabilised at 2.1 Ω. Multi-angle steering wheel test: no abnormalities. Fault completely resolved.
BYD DTC AI AnalysisFrom Chinese market (translated)

Replaced airbag module due to internal resistor aging

✓
2019 Qin Pro (petrol). B161C1B fault occurred repeatedly. Wiring measured normal at 2.2 Ω, but the fault returned when driving over bumps. Monitored with an oscilloscope and found instantaneous resistance spikes. Found internal igniter resistance degradation or dry solder joints in the front passenger airbag module. Replaced the front passenger airbag module (fitted new fixing bolts, torqued to 9–11 N·m). Coded the new module using VDS. Fault resolved.
BYD DTC AI AnalysisFrom Chinese market (translated)

Wiring harness under seat chafed, causing intermittent connection.

✓
2019 Qin Pro DM with seat position sensor: Frequent front-to-back seat adjustment chafed the floor harness against the guide rail, partially breaking internal copper strands and creating a high-resistance connection that triggered B161C1B. Inspected the wiring under the seat; found damaged insulation and oxidised copper. Cut out the damaged section, soldered in a matching-gauge wire, applied double-layer heat shrink tubing, and rerouted the harness away from moving parts. Resistance stabilised at 2.0 Ω after repair. Fault resolved.
Other Qin Plus 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]