AU
B1601

DTC B1601 indicates a short to ground in the driver frontal airbag (DAB) ignition circuit — Seal U

Safety System

DTC B1601 indicates a short to ground in the driver frontal airbag (DAB) ignition circuit.

In the BYD SRS (Supplemental Restraint System), this fault means damaged wire insulation in the circuit between the airbag control unit (ACU) and the driver airbag contacts the vehicle body ground, or an internal short to ground exists within the airbag inflator.

This causes circuit resistance to drop well below the standard range (normally 2.0-3.0 Ω, approaching 0 Ω during a short circuit).

When the ACU detects this abnormal drop in circuit impedance, it identifies a short-to-ground fault and triggers protection mode: the instrument cluster SRS warning light illuminates continuously, the system disables the driver airbag to prevent inadvertent deployment, and the airbag fails to deploy during a collision, severely compromising occupant safety.

3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1A worn or broken flat cable inside the clock spring shorts the wire to the steering wheel metal frame or ground wire.
  • 2Water ingress, corrosion, or deformed pins at the yellow airbag wiring harness connector below the steering wheel (usually near the combination switch), causing the terminal to short to ground.
  • 3Chafing or crushing damages the insulation on the wiring harness from the ACU to the steering wheel where it passes through the A-pillar, dashboard, or floor, causing a short to body ground.
  • 4Internal fault in the driver airbag module (inflator igniter) causing one of the two igniter terminals to short to ground.
  • 5Airbag control module (SRS ECU) internal driver circuit fault, incorrectly reporting a short to ground (confirm after ruling out external wiring).
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS backup power supply and prevent accidental airbag deployment.
  • 2
    Fault Confirmation: Connect BYD VDS or a factory diagnostic tool. Read DTC B1601 and freeze frame data. Confirm the fault status is Current and record the vehicle status when the fault occurred.
  • 3
    Visual inspection: Check the yellow airbag wiring harness connector under the steering wheel for looseness, water ingress, oxidation, or damage. Check the clock spring exterior for burn marks.
  • 4
    Airbag module isolation test: Remove the driver airbag, measure the resistance between the two terminals of the airbag connector (normal: 2.0-3.0Ω), and measure the resistance from each terminal to ground (should be infinite; if continuity exists, the airbag has an internal short circuit; replace the airbag).
  • 5
    Clock spring test: Disconnect the connectors and measure continuity between the clock spring upstream (ACU side) and downstream (airbag side). Measure the insulation to ground for each terminal. Rotate the steering wheel to check for intermittent shorts to ground.
  • 6
    Harness continuity and insulation test: Use a multimeter to measure the harness from the ACU to the steering wheel and check for continuity to ground. Inspect the harness routed through the A-pillar and floor for wear or damaged insulation.
  • 7
    Component replacement: Replace the faulty component (clock spring, wiring harness, or airbag assembly) based on the test results. After replacing the clock spring, center the steering wheel to prevent abnormal angle sensor data after installation.
  • 8
    System reset and verification: Reconnect all connectors and the battery. Use the diagnostic tool to clear the DTC. Perform an SRS system self-check to confirm B1601 does not return. Road test the vehicle to confirm the SRS warning light remains off.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Internal wear of the clock spring caused a short to ground.

✓
A 2020 BYD Song Pro with 42,000 km on the odometer came in with the airbag warning light constantly illuminated. A VDS scan revealed current fault code B1601 (driver frontal airbag short to ground). The technician disconnected the battery negative terminal, waited 90 seconds, then removed the driver airbag. The airbag itself measured 2.3Ω (normal), and its terminal-to-ground resistance was infinite (normal). Next, the technician checked the clock spring. Measurements were normal with the steering wheel straight ahead, but when turned to full left or right lock, the downstream clock spring terminals intermittently showed 0Ω to ground. This confirmed internal wear of the ribbon cable causing a short to ground. The technician replaced the clock spring (Part No.: BYD-EG-5910XXX), reinstalled the steering wheel ensuring it was centered, cleared the fault codes, and the SRS system passed its self-test; the warning light went out. A road test confirmed the repair.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Connector corrosion after wading caused short to ground

✓
A 2019 BYD Yuan EV had the airbag warning light illuminate after driving through heavy rain and flood water. The scan tool showed current fault code B1601. Inspection revealed water stains and verdigris corrosion inside the yellow airbag harness connector (C202 plug) below the steering wheel. One terminal had corroded and broken off, contacting the connector's metal housing and creating a short to ground. The resistance from that terminal to ground measured 0.2Ω. Repair steps: cleaned the connector thoroughly with electronic cleaner, dried the harness with compressed air, replaced the damaged terminal and re-crimped it, applied conductive anti-corrosion compound, and reconnected the plug. Also checked the floor harness sealing and found that the aged weatherstrip at the base of the A-pillar was allowing water entry; the technician resealed the area with fresh sealant. After clearing the fault codes and road testing, the fault did not recur.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Internal short circuit in airbag assembly after accident repair

✓
A 2021 BYD Qin Plus DM-i was in a front collision. A repair shop replaced the driver airbag with a used unit. After the repair, the SRS warning light stayed on, and a scan tool read DTC B1601. The technician disconnected the battery, removed the airbag, and measured 2.1 Ω across its terminals — a reading that seemed normal. However, when measuring resistance from each terminal of the airbag connector to body earth, one terminal showed 0 Ω, confirming a short-to-earth fault in the used airbag's internal igniter. The technician replaced the driver airbag with a new genuine assembly. (Note: verify the part number matches the vehicle; some models also require replacing the seatbelt pretensioners.) After installation, the circuit resistance returned to normal (2.5 Ω). The technician connected the scan tool, cleared the DTC, and performed SRS system configuration and self-test. Fault resolved.
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]