AU
B1611

DTC B1611 indicates a short to ground in the front passenger airbag (PAB) ignition circuit — Seal U

Safety System

DTC B1611 indicates a short to ground in the front passenger airbag (PAB) ignition circuit.

Specifically, the SRS control unit detects an abnormally low-resistance connection (typically less than 2-3Ω) between the passenger airbag inflator circuit (usually the high-level trigger wire) and vehicle ground (GND).

This short circuit prevents normal airbag deployment (diverting ignition energy to ground) or, in extreme cases, causes inadvertent deployment due to static electricity or electromagnetic interference.

This fault constitutes a severe active safety system failure.

The SRS control unit immediately disables the front passenger airbag, illuminates the airbag warning light, and may simultaneously lock the seat belt pretensioner, severely compromising passive safety performance.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Passenger-side dashboard wiring harness wear: Long-term vibration damages the airbag wiring harness insulation where it routes through the dashboard frame or near the steering column, causing contact with the metal body and creating a short to ground.
  • 2Connector water ingress and corrosion: The airbag connector (usually yellow) located under the centre console or on the floor lacks proper sealing. After driving through water or an A/C condensate leak, electrolytic corrosion forms between the pins, causing a short to ground.
  • 3Service damage: Tools scratching or crushing the wiring harness during A/C filter replacement, radio replacement, or dashboard removal and installation, damaging the wire insulation and causing it to contact metal body parts.
  • 4Internal airbag module fault: Damaged insulation on the igniter bridge wire inside the front passenger airbag assembly shorts the ignition terminal to the airbag metal housing (ground). This condition typically follows moisture ingress into the airbag assembly.
  • 5Rodent damage: During long-term outdoor or warehouse parking, rodents chew through the wiring harness insulation, exposing the copper core and causing it to contact the vehicle body ground.
What To Do
  • 1
    Safety preparation and diagnostic confirmation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor. Use the diagnostic tool to read freeze frame data and confirm vehicle status at the time of the fault (temperature, vehicle speed, etc.). Check for accompanying fault codes (such as B1610, B1612, etc.).
  • 2
    Visual inspection and connector check: Remove the lower trim panel under the front passenger glovebox. Check the yellow SRS connector (usually marked F-PAB) for water ingress, corrosion, or deformed pins. Measure the resistance from the connector terminals to ground. The normal value is greater than 10 MΩ.
  • 3
    Harness continuity check: Test harness continuity from the SRS ECU to the front passenger airbag, focusing on sections passing the Cross Car Beam and the floor harness sleeve. Use an endoscope to inspect the harness for wear at metal edges.
  • 4
    Airbag module test: Replace the front passenger airbag with a dedicated airbag simulator (2Ω load). Clear the fault code and power on the system. If the fault code disappears, the airbag assembly has an internal short circuit. Replace the front passenger airbag module.
  • 5
    Repair and verification: Repair the damaged wiring harness (wrap with double-layer heat-shrink tubing). Secure the wiring harness, maintaining a minimum 20mm clearance from metal components. Apply conductive paste and reconnect all connectors. Connect the battery. Use the diagnostic tool to execute 'System Configuration' and 'Sensor Calibration'. Finally, perform a collision simulation test to verify fault resolution.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Song MAX dashboard wiring harness wear caused intermittent short circuit

✓
A 2019 BYD Song MAX with 32,000 km had an intermittent airbag warning light and DTC B1611. Technicians found the passenger side airbag wiring harness had chafed through at the dashboard crossmember clip due to prolonged vibration, exposing the copper core. When the vehicle encountered bumps or temperature fluctuations, the exposed wiring contacted the crossmember causing a short to earth. Technicians repaired the damaged wiring (approximately 15 cm), rerouted the harness away from sharp edges, and fitted a rubber protective sleeve. This permanently resolved the fault.
BYD DTC AI AnalysisFrom Chinese market (translated)

Tang DM air conditioning condensate leak corroded connector

✓
2021 Tang DM. After heavy rain, the airbag warning light stayed on. Scan tool read DTC B1611 and could not clear it. Inspection found obvious water stains on the passenger-side floor harness connector (beneath the evaporator box). Resistance between Pin 1 (airbag high signal) and the connector shell (ground) was only 0.8 Ω. Traced to a blocked AC drain hose causing condensate to back up. Repair: cleaned and dried connector, treated pins with WD-40 Precision Electrical Cleaner, cleared drain hose, and applied sealant around the connector.
BYD DTC AI AnalysisFrom Chinese market (translated)

Yuan EV wiring harness improperly secured after accident repair

✓
One week after completing front collision repairs on a 2019 Yuan EV, the vehicle logged a B1611 DTC. Service history showed a previous replacement of the instrument panel assembly. Inspection found the passenger airbag harness pinched between the instrument panel bracket and body shell during reinstallation, crushing the insulation and creating an earth short. Replaced the damaged harness section (from instrument panel main harness to airbag connector). Reinstalled the instrument panel to the workshop manual torque of 9.8 N·m and fitted dedicated harness clips to maintain safe clearance from metal components.
BYD DTC AI AnalysisFrom Chinese market (translated)

Long-term parking caused rodents to chew the wiring harness on the Qin Pro.

✓
2020 Qin Pro. After sitting parked in a rural yard for two weeks, the airbag warning light illuminated on startup. Diagnosis revealed DTC B1611. Inspection of the wiring passthrough between the engine bay and passenger cabin found the harness sheath chewed through, with multiple bite marks on the internal airbag wiring. One wire had exposed copper contacting the body metal. Repair: cut out the damaged section, soldered in an extension wire, and insulated the repair with double-layer heat shrink tubing. Installed metal rodent-proof mesh at the wiring grommet and applied capsaicin-based rodent repellent to the harness surface.
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]