AU
B17081A

DTC B17081A indicates the LHS Curtain Shield Airbag ignition circuit resistance is 0 ohms, representing a short circuit — Seal U

Safety System

DTC B17081A indicates the LHS Curtain Shield Airbag ignition circuit resistance is 0 ohms, representing a short circuit.

In the BYD SRS (Supplemental Restraint System), normal curtain airbag inflator resistance is 1.8-2.5 Ω.

A 0 Ω resistance indicates a short to ground in the ignition wiring between the SRS control unit and the LHS curtain airbag, or an internal short circuit within the inflator.

This fault prevents the LHS curtain airbag from deploying during a collision.

The control unit disables the shorted circuit to prevent accidental deployment and illuminates the airbag warning lamp.

The short circuit can trigger a protective lockout of the SRS control unit, which in severe cases affects the normal operation of the entire airbag system.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Internal short circuit in the left side curtain airbag inflator: Moisture, aging, or manufacturing defects cause a short circuit between the positive and negative terminals of the igniter bridge wire inside the curtain airbag assembly.
  • 2Wiring harness chafed and shorted to ground: Long-term vibration and friction damage the wiring harness insulation in the A-pillar, B-pillar, or headliner, causing a short circuit to the vehicle body metal.
  • 3Connector fault: Water ingress, corrosion, or bent pins making contact in the curtain airbag connector (usually located in the headliner or C-pillar) causing a short circuit.
  • 4SRS control unit internal driver circuit fault: The internal ignition driver transistor broke down, causing a short circuit.
  • 5Improper repair work: piercing the curtain airbag wiring harness with a tool or incorrectly seating the connector during previous headliner removal/installation, glass replacement, or A-pillar trim removal/installation.
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes to fully discharge the SRS capacitor; disable the high-voltage system (if applicable).
  • 2
    Initial diagnosis: Use a dedicated diagnostic tool (e.g., VDS2000/3000) to read freeze frame data and confirm environmental conditions when the fault occurred. Clear the fault code, cycle the ignition, and observe if it is a current fault (Current DTC).
  • 3
    Circuit measurement: Disconnect the SRS ECU and left curtain airbag connectors. Use a multimeter to measure the curtain airbag-side wiring harness resistance to ground and confirm if it is 0 Ω. Measure the curtain airbag resistance (should be 1.8-2.5 Ω). If the resistance is 0 Ω, replace the curtain airbag assembly.
  • 4
    Wiring harness inspection: Check the headliner wiring harness (especially the A-pillar to C-pillar section) for wear or pinch marks; check connector sealing and terminal condition; measure wiring harness insulation resistance to ground, which must be greater than 1MΩ.
  • 5
    ECU check: If the wiring harness and curtain airbag are normal, measure the output at the corresponding SRS ECU pin. If the measurement still indicates a short circuit, replace the SRS control unit.
  • 6
    Repair verification: After repairing the short circuit, use a 2Ω substitute resistor (special diagnostic tool) to simulate the curtain airbag. Verify the fault code clears and the system returns to normal. Finally, connect the actual curtain airbag and perform 3 ignition cycle self-checks to verify the system outputs no fault codes.
Real-World Cases
BYD DTC AI Analysis

Left curtain airbag inflator internal short circuit case

✓
Model: BYD Qin EV 2019. Symptom: Instrument panel airbag warning light stays on constantly; read DTC B17081A. Diagnosis: Disconnected the battery, removed the left curtain airbag connector, measured resistance across the airbag terminals: 0.2 Ω (normal: approx. 2 Ω), confirming an internal short in the curtain airbag. Fix: Replaced the left curtain airbag assembly, rewound the airbag using special tools to prevent wrinkles after installation, and cleared the fault.
BYD DTC AI Analysis

Headlining wiring harness chafed, short to ground.

✓
Model: BYD E2 2019. Symptom: Airbag warning light illuminated after driving over rough roads, DTC B17081A stored. Diagnosis: Checked curtain airbag unit — normal. Traced the roof wiring harness and found a loose retaining clip above the A-pillar. The harness had chafed against the metal bracket, damaging the insulation and exposing copper wires that shorted to body. Repair: Repaired the damaged harness by wrapping with insulation tape and covering with corrugated sleeving. Re-secured harness routing and ensured adequate clearance from sharp edges.
BYD DTC AI Analysis

C-pillar connector water ingress corrosion

✓
Model: BYD E3 2020. Symptoms: Airbag warning light illuminated after rain; intermittent DTC B17081A. Diagnosis: Inspected the left curtain airbag C-pillar connector (located within the trim panel above the rear seat). Found the connector seal degraded and pins showing green copper corrosion, causing a short circuit between terminals. Fix: Cleaned the connector pins using electrical contact cleaner, replaced the seal, and applied waterproof silicone grease to the connector to ensure waterproof performance.
BYD DTC AI Analysis

SRS control unit internal driver fault

✓
Model: BYD Qin EV 2019. Symptoms: The fault persisted after multiple left curtain airbag and wiring harness replacements. DTC B17081A was current and could not be cleared. Diagnostic process: Disconnected the curtain airbag and wiring harness, then directly measured the corresponding output pins on the SRS ECU. Resistance to ground was 0 Ω, confirming a short circuit in the control unit's internal ignition drive circuit. Solution: Replaced the SRS control unit (required re-coding of vehicle configuration and crash sensor calibration). Fault resolved.
BYD DTC AI Analysis

Improper removal and installation pinched the wiring harness, causing a short circuit.

✓
Vehicle: BYD E2 2019. Symptoms: After the dealership replaced the headliner, fault code B17081A appeared upon delivery. Diagnosis: Inspection revealed the A-pillar trim clip pinched the left curtain airbag wiring harness during A-pillar trim installation, causing an internal short circuit. Resolution: Repaired the damaged harness by cutting out the affected section and soldering in an extension, rerouted the harness to clear the trim clip mounting points, and reinstalled the A-pillar trim.
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.