UK
AU
B1706-00

This DTC indicates the Airbag Control Unit (ACU) detects an abnormal short circuit between the ignition drive circuit of the Left Side Curtain Airbag (located inside the driver-side roof side rail) and the vehicle constant power supply (B+) — Seal 6 EV

Safety System

This DTC indicates the Airbag Control Unit (ACU) detects an abnormal short circuit between the ignition drive circuit of the Left Side Curtain Airbag (located inside the driver-side roof side rail) and the vehicle constant power supply (B+).

Under normal conditions, the ACU internal boost circuit supplies a high-voltage pulse to the airbag ignition circuit only at the moment of deployment, and the circuit remains insulated from body ground and power lines.

When the diagnostic system detects a continuous 12V battery voltage in this circuit, it identifies a short to power.

This fault causes the ACU to trigger primary/secondary safety protection and disable the left curtain airbag circuit to prevent accidental deployment, resulting in a loss of head protection during a side-impact collision.

If the short-circuit current reaches the deployment threshold, extreme cases may cause unexpected airbag deployment, constituting a severe safety defect.

5
Cases Logged
Real-World Cases
BYD DTC AI Analysis

A-pillar trim screw pinching damaged the wiring harness.

✓
A 2017 Qin EV300 exhibited an airbag warning light that stayed on after accident repairs. Diagnosis confirmed active fault code B1706-00. Getting under the left A-pillar trim revealed that the trim panel screws replaced during the accident repair were too long, piercing the outer insulation of the left curtain airbag harness. This shorted the yellow igniter wire to the red constant-power wire for the reading lamp. Repair: Replaced the damaged harness section (the complete main harness from the ACU to the curtain airbag), sleeved it with genuine convoluted tubing for added protection, and installed standard-length screws. Fault cleared.
BYD DTC AI Analysis

Sunroof drain tube leak caused connector corrosion

✓
A 2018 Qin EV450 had an airbag warning light on after the rainy season. The owner reported water stains on the left headliner. Inspection revealed DTCs B1706-00 accompanied by B1707-00 (right curtain airbag short to ground). Removed the C-pillar trim and found severe corrosion on the left curtain airbag connector, with verdigris between the pins shorting positive to negative. Traced the leak to a detached left rear sunroof drain hose, allowing rainwater into the C-pillar. Repaired the drain hose connection, thoroughly dried the C-pillar interior, cleaned the connector with precision electronics cleaner, applied dedicated conductive grease, and replaced the curtain airbag wiring harness plug. Fault resolved.
BYD DTC AI Analysis

Aftermarket headliner ambient lighting caused circuit interference.

✓
A 2017 BYD Qin 100’s airbag warning light illuminated after an auto accessory shop installed aftermarket interior roof ambient lighting. The system stored DTC B1706-00. Inspection found the installer had bundled the ambient lighting power feed (constant power) together with the left curtain airbag harness using cable ties, and secured the light strip with metal self-tapping screws. The screws pierced the airbag harness insulation, causing a short circuit. Fix: removed the non-compliant ambient lighting and wiring, repaired the damaged curtain airbag harness by soldering and heat-shrink tubing, restored the original harness routing, and cleared the DTCs. The system returned to normal.
BYD DTC AI Analysis

Internal driver chip shorted in airbag control unit

✓
A 2017 Qin 80 with no accident or modification history suddenly had the airbag warning light come on while driving, displaying DTC B1706-00. Measured the left curtain airbag drive terminal at the ACU connector: constant 12V output. Disconnected the connector and measured continuity from the ACU internal to the curtain airbag terminal, confirming the internal ignition drive circuit had shorted. Replaced the airbag control unit (ACU). Ran the 'ECU Replacement' procedure using VDS, wrote the vehicle VIN and configuration, and executed a system self-test. Fault resolved.
BYD DTC AI Analysis

Seat adjustment mechanism rubbing against wiring harness

✓
A 2018 BYD Qin EV450 developed an intermittent DTC B1706-00, particularly after adjusting the driver's seat height. Inspection found the left curtain airbag wiring harness routed too close to the seat frame below the B-pillar. When the seat was raised to its highest position, the seat frame edge chafed against the harness, wearing through the insulation and exposing the copper wire, which shorted to the seat motor power line. We rerouted the harness, secured it clear of the seat track using dedicated harness retaining clips, fitted protective sleeving at the wear point, and replaced the damaged harness section.
Other Seal 6 EV 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: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.