AU
B160B

DTC B160B indicates the SRS (Supplemental Restraint System) control unit detects the driver frontal airbag (DAB) igniter (squib) circuit resistance is below the calibrated threshold (typically <1 — Seal U

Safety System

DTC B160B indicates the SRS (Supplemental Restraint System) control unit detects the driver frontal airbag (DAB) igniter (squib) circuit resistance is below the calibrated threshold (typically <1.5Ω; standard range is 2.0±0.3Ω).

This active fault indicates an abnormally low-resistance path in the circuit.

A partial short circuit, an internal turn-to-turn short in the igniter, or a wiring harness short to ground can cause this condition.

The low resistance abnormally increases the airbag circuit current, creating a risk of unintended airbag deployment.

Alternatively, during a collision, the excessive current may trigger the ACU protective cutoff and prevent normal deployment.

When this DTC triggers, the SRS system typically enters fail-safe mode and disables the driver-side airbag.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Turn-to-turn short circuit or wear in the clock spring (spiral cable) internal coil reduces effective resistance. This is a common fault point on BYD models, especially the Tang and Song series.
  • 2Internal short circuit in the driver airbag module (DAB) igniter, or moisture in the pyrotechnic charge causing resistance drift. Typically occurs after vehicle water ingress or exposure to high-temperature, high-humidity environments.
  • 3Airbag wiring harness short to ground or power supply, often resulting from a damaged wiring sheath below the steering wheel, a pinched harness during steering wheel modification, or backed-out terminal pins.
  • 4Internal fault in the SRS control unit (ACU) sampling circuit or reference resistor drift, causing a false low resistance reading. Rule out via cross-checking.
  • 5Connector water ingress or terminal corrosion (e.g., poor sealing under the steering wheel on Yuan EV and Qin models) creates a parallel resistance path, reducing total resistance.
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (to fully discharge the ACU capacitor). Never measure the airbag terminals directly with a multimeter in resistance mode (the current may trigger airbag deployment).
  • 2
    Initial diagnosis: Connect the VDS or BYD dedicated diagnostic tool, read the DTC status (current/history), record the resistance value in the freeze frame data (such as 0.8Ω or 1.2Ω), and confirm fault persistence.
  • 3
    Visual inspection: Check the wiring harness sleeve below the steering wheel and the clock spring connector (usually yellow) for damage, signs of water ingress, or modification. Check the airbag terminals for oxidation.
  • 4
    Sectional resistance measurement: Disconnect the clock spring from the airbag. Use a dedicated airbag tester or connect a 2Ω dummy load in series to separately measure the resistance of the airbag assembly itself and the wiring harness circuit to locate the faulty section.
  • 5
    Component isolation test: Move the driver airbag module to the front passenger position (for testing only). If the fault code changes to B160C (front passenger resistance too low), the airbag module is faulty. If it remains B160B, check the clock spring or wiring harness.
  • 6
    Clock spring inspection: Measure the clock spring resistance at different rotation angles. If the resistance fluctuates while turning the steering wheel or drops below 1.0 Ω, an internal short circuit exists. Replace the clock spring.
  • 7
    Repair and Verification: After replacing the faulty component, use the diagnostic tool to perform 'Crash Sensor Calibration' and 'System Self-test'. Confirm the resistance returns to the 2.0±0.3Ω range. Clear the fault code and perform an ignition-on cycle test.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Tang DM clock spring internal short circuit resulting in 0.9Ω resistance.

✓
2021 Tang DM. The dash showed an 'Airbag Fault'. Retrieved DTC B160B. Live data indicated the driver's airbag resistance at 0.9Ω. Disassembled the steering wheel and found slight water ingress on the clock spring connector. Removed the clock spring and measured the resistance: 1.2Ω at rest, dropping to 0.6Ω when turning the steering wheel. Determined the internal flat cable insulation had worn, causing a short. Installed a genuine clock spring (part number: KE-4135100). Resistance returned to 2.1Ω. Fault resolved.
BYD DTC AI AnalysisFrom Chinese market (translated)

Song MAX airbag connector corroded after wading

✓
2019 Song MAX. After a typhoon, the airbag warning light stayed on constantly and stored DTC B160B. Inspection found muddy water intrusion in the wiring harness connector below the driver-side A-pillar (airbag circuit branch). The terminals showed green oxidation, causing approximately 0.5Ω parallel resistance. Cleaned terminals using electronic contact cleaner, applied conductive anti-corrosion grease, and replaced the waterproof seal ring. Resistance returned to normal. Recommend checking the door weatherstrip drain holes for blockages.
BYD DTC AI AnalysisFrom Chinese market (translated)

Modified steering wheel on Yuan EV crushed the wiring harness

✓
2019 BYD Yuan EV. One week after the owner fitted a racing steering wheel, DTC B160B set. Inspection found the aftermarket adapter hub was too thin, causing the original airbag wiring harness to be excessively pinched at the steering wheel frame. This damaged the insulation and created a short to ground. Repaired the wiring harness and fitted a dedicated harness protection sleeve. After restoring the factory steering wheel, the fault cleared. Tip: When fitting an aftermarket steering wheel, make sure the clock spring and airbag wiring harness have enough clearance.
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin Pro ACU software falsely reporting low resistance

✓
2020 BYD Qin gasoline. Intermittent B160B. Measured airbag resistance: 2.0Ω (normal). Checked ACU software version: V1.2. Known issue: overly sensitive sampling algorithm threshold. Flashed ACU to V2.1 using VDS (ECU refresh), which lowers the resistance detection threshold lower limit to 1.2Ω. Fault did not return. This type of software fault needs confirmation by comparing with multiple vehicles from the same production batch.
BYD DTC AI AnalysisFrom Chinese market (translated)

Internal short circuit in driver airbag igniter due to aging

✓
2019 Yuan, 80,000 km. DTC B160B persistent, resistance 1.0 Ω. Disconnected the clock spring and measured the airbag assembly directly; resistance remained low. Disassembled the airbag and found the insulation between the igniter bridge wire and housing had aged and broken down. Replaced the driver airbag assembly. Airbags are hazardous explosives—handle the old part in accordance with explosives transport regulations. Fault resolved. This fault occurs more frequently in high-temperature regions such as Hainan and Guangdong.
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]