AU
B170F12

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

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.

The B170F12 fault code on the Seal U indicates a high-severity short to power in the right side curtain airbag ignition circuit. This can affect airbag deployment or disable related SRS functions. Common causes include damaged wiring insulation in the pillar or roof area, or a faulty curtain airbag connector with water ingress, corrosion, or bent pins. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Damaged right curtain airbag wiring harness insulation: Long-term vibration, compression, or external force damages the harness insulation inside the A-pillar, B-pillar, or roof side rail, causing it to contact the body power wire and short circuit.
  • 2Curtain airbag connector fault: Water ingress, oxidation, or pin deformation at the curtain airbag connector inside the B-pillar trim causes a short circuit between pins (especially between the high-side drive pin and the constant power pin).
  • 3Damage from modifications or aftermarket equipment: Fixing screws or wiring harness clips pierce the original curtain airbag wiring harness during the installation of a dash cam, roof ambient lighting, or upgraded audio system.
  • 4Internal short circuit in the curtain airbag assembly: Damaged insulation on the gas generator igniter resistance wire causes a short circuit to the housing (the housing normally grounds, but on some models, the curtain airbag housing may abnormally contact the positive power supply through the mounting points).
  • 5SRS control unit internal fault: The airbag ignition driver chip inside the ACU (such as the high-side switch MOSFET) shorted, resulting in continuous ignition voltage output.
What To Do
  • 1
    Safety preparation: Turn the vehicle OFF, disconnect the 12V battery negative terminal, wait at least 90 seconds (to ensure the SRS capacitor fully discharges), 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, focusing on the sill trim strip and roof side rail fixing clips.
  • 3
    Connector inspection: Disconnect the right curtain airbag connector (usually located in the middle of the B-pillar or C-pillar). Check the pins for oxidation, deformation, or water stains. Measure the resistance to ground and voltage to power supply at the connector's body-side wiring harness terminals.
  • 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 body power supply (+B). 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, substitute the right curtain airbag with the dedicated airbag substitute resistor (2Ω). 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. Use the diagnostic tool to clear the fault code. Perform the 'Sensor Check' and 'Airbag System Self-check'. 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 Seal U Fault Codes
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.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173712DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Common problems reported for Seal U →Seal U overview →
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.