AU
B170F12

DTC B170F12 indicates a short to power in the right side curtain airbag ignition circuit — Atto 8

Safety System

DTC B170F12 indicates a short to power in the right side curtain airbag ignition circuit.

In the BYD SRS (Supplemental Restraint System) architecture, this fault indicates the airbag control unit (ACU) detects an abnormally low-impedance connection between the right side curtain airbag igniter circuit (typically two wires: high-side driver and low-side driver) and the vehicle power supply (+12V or +B).

This hardware short-to-battery fault may cause: 1) risk of unintended airbag deployment (in extreme cases); 2) airbag failure to deploy during a collision; 3) the SRS entering protection mode, disabling related airbag functions.

The '12' suffix in the BYD diagnostic protocol typically designates the specific 'short to power' subtype.

5
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Right curtain airbag wiring harness insulation damage: Long-term vibration, compression, or external impact damages the harness insulation inside the A-pillar, B-pillar, or roof side rail, shorting the harness to the body power supply wire.
  • 2Curtain airbag connector fault: Water ingress, oxidation, or deformed pins in the curtain airbag connector located inside the B-pillar trim cause a short circuit between pins (especially between the high-side drive pin and constant power pin).
  • 3Damage from modifications or added equipment: Fixing screws or harness clips pierced the factory curtain airbag wiring harness during the installation of a dash cam, roof ambient lighting, or aftermarket audio system.
  • 4Curtain airbag assembly internal short circuit: Damaged insulation on the gas generator igniter resistance wire causes a short circuit to the housing (the housing typically grounds to the chassis, but on some models, the curtain airbag housing may abnormally contact the positive power supply through its mounting points).
  • 5SRS control unit internal fault: The airbag ignition driver chip inside the ACU (such as the high-side switch MOSFET) short-circuits, causing continuous ignition voltage output.
What To Do
  • 1
    Safety preparation: Switch the vehicle OFF, disconnect the 12V battery negative terminal, wait at least 90 seconds (to fully discharge the SRS capacitor), and wear an anti-static wrist strap.
  • 2
    Visual inspection: Remove the right A-pillar, B-pillar, and headliner trim panels. Inspect the curtain airbag wiring harness for damage or burn marks. Focus on the sill trim and roof side rail retaining clips.
  • 3
    Connector check: Disconnect the right curtain airbag connector (usually located in the middle of the B-pillar or C-pillar). Inspect the pins for oxidation, deformation, or water stains. Measure the resistance to ground and voltage to power at the vehicle-side harness terminals of the connector.
  • 4
    Circuit continuity test: Use a multimeter to measure continuity between the two curtain airbag circuit wires (usually marked R-CAB+ and R-CAB-) and the vehicle power supply (+B). The normal reading is infinity (OL).
  • 5
    Insulation resistance test: Use a megohmmeter (500V range) to measure the insulation resistance between the curtain airbag wiring harness and the vehicle body. The resistance must be greater than 10MΩ.
  • 6
    Component isolation test: If the wiring harness is normal, connect a dedicated airbag substitute resistor (2Ω) in place of the right-side curtain airbag. Clear the fault code, power on, and test. If the fault disappears, replace the curtain airbag assembly.
  • 7
    Control unit inspection: If all above checks are normal, inspect the ACU connector and internal circuits. If necessary, replace the SRS control unit and perform coding matching.
  • 8
    Repair verification: After repair, reconnect the battery and use the diagnostic tool to clear the fault code. Perform the 'Sensor Check' and 'Airbag System Self-test'. Confirm B170F12 does not return and the SRS warning light turns off normally.
Real-World Cases
BYD DTC AI Analysis

Chafed B-pillar wiring harness caused short to power.

✓
A 2019 BYD Qin Pro DM with 30,000 km had the SRS warning light on. Retrieved DTC B170F12. Removed the right-side B-pillar trim and found the curtain airbag harness insulation worn through at the clip location, with exposed copper wires contacting a constant power wire on the body. The cause was a missing harness clip that allowed the harness to rub and wear through. Repaired the damaged wiring, rerouted and secured the harness, and resolved the fault.
BYD DTC AI Analysis

Sunroof leak caused a short circuit in the curtain airbag connector.

✓
The owner of a 2020 E3 reported the airbag warning light illuminated on the dashboard after rain. Inspection found visible water stains inside the right-side C-pillar curtain airbag connector; oxidised pins caused a short circuit. Further checks found the sunroof drain hose detached, letting rainwater into the C-pillar. Cleaned the water stains, replaced the curtain airbag connector (repaired the pins), reinstalled the drain hose, and cleared the fault.
BYD DTC AI Analysis

Aftermarket dash cam installation pierced wiring harness

✓
2019 E2 logged B170F12 the day after an aftermarket shop installed a dashcam. Inspection found a self-tapping screw used during the wiring work had pierced the right-hand roof curtain airbag harness, causing a short between the power wire and airbag igniter line. Repaired the damaged harness (soldered and insulated with heat-shrink tubing), rerouted the dashcam wiring clear of the airbag loom, and resolved the fault.
BYD DTC AI Analysis

Internal short circuit in curtain airbag igniter

✓
A 2018 Qin Pro petrol was in a right-side collision. A repair shop fitted an aftermarket right curtain airbag, after which the vehicle logged DTC B170F12. The replacement airbag showed normal resistance, but the fault remained after installation. Disassembly and inspection revealed the aftermarket airbag's internal igniter had defective insulation, causing a short to the housing (the housing had an unintended electrical path to body power via the mounting bracket). Installing a genuine right curtain airbag assembly fixed the fault.
BYD DTC AI Analysis

SRS control unit driver chip fault

✓
A 2019 Qin EV with no accident history developed intermittent SRS warning light illumination during normal use, with DTC B170F12 appearing sporadically. Inspection of the wiring harness and connectors found no faults, and wiggling the harness did not reproduce the fault. Measuring the ACU output terminals revealed abnormal voltage leakage at the right side curtain airbag drive terminal. The cause was poor thermal stability of the high-side driver chip inside the SRS control unit. Replacing the SRS control unit and performing online programming (VDS2000 or a dedicated diagnostic tool) completely resolved the fault.
Other Atto 8 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.