AU
B170A1B

This DTC indicates the Supplemental Restraint System (SRS) detected the igniter (squib) circuit resistance of the left curtain shield airbag (located above the driver-side window between the B-pillar and C-pillar) exceeds the calibrated threshold (typically >3 — Atto 3

Safety System

This DTC indicates the Supplemental Restraint System (SRS) detected the igniter (squib) circuit resistance of the left curtain shield airbag (located above the driver-side window between the B-pillar and C-pillar) exceeds the calibrated threshold (typically >3.6Ω, normal range 1.5-3.0Ω).

Excessive resistance usually indicates a high-resistance connection, a partial open circuit, poor connector contact, or an internal open circuit in the igniter.

This fault may prevent the left curtain shield airbag from deploying during a side impact and continuously illuminates the SRS warning light.

This is a critical fault affecting passive safety.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Loose left lower A-pillar curtain airbag wiring harness connector (yellow plug), backed-out pins, or oxidized terminals, causing increased contact resistance.
  • 2Internal open circuit or poor contact in the spiral cable (clock spring) disrupts signal transmission in the curtain airbag circuit (on some models, the curtain airbag circuit routes near the steering column).
  • 3Internal open circuit or aging failure of the curtain airbag inflator, causing infinite or abnormally high circuit resistance.
  • 4Airbag Control Module (ACM/SRS ECU) internal detection circuit fault, abnormal sampling resistor, or connector pin corrosion.
  • 5Repeated bending and wear of the body wiring harness at the A-pillar or B-pillar pass-through hole breaks copper strands, creating a high-resistance connection.
What To Do
  • 1
    Safety preparation: Switch the vehicle OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 2
    Fault confirmation: Use the BYD VDS diagnostic tool to read freeze frame data, confirm the exact current resistance value of the left curtain airbag (e.g., 3.8Ω or OL open circuit), and check for intermittent faults.
  • 3
    Visual inspection: Remove the left A-pillar trim panel and front roof trim panel. Verify the curtain airbag wiring harness connector (yellow waterproof plug) is fully locked. Inspect for water ingress, oxidation, burn marks, or terminal back-out.
  • 4
    Wiring check: Disconnect the ACM connector. Use a dedicated low-current ohmmeter (<10mA) to measure harness continuity from the ACM pin to the curtain airbag connector. Normal resistance is <1Ω. Check the harness insulation for wear at the A-pillar pass-through hole.
  • 5
    Component isolation test: Connect an SRS simulator resistor (2Ω) to the circuit in place of the curtain airbag. If the fault code clears, the curtain airbag is faulty. If the code remains, check the wiring harness or ACM.
  • 6
    Repair/Replace: Repair the damaged wiring harness and re-wrap with anti-abrasion tape. Replace the faulty curtain airbag assembly (simultaneously replace the retaining clips and bolts with new ones). Replace the ACM if necessary.
  • 7
    System verification: Reconnect the battery, clear the fault code, and perform an SRS system self-check (turn the ignition switch ON and verify the warning light illuminates and then turns off). Use VDS to read the current resistance and confirm it returns to the normal range (1.5-3.0Ω).
Real-World Cases
BYD DTC AI Analysis

Qin PRO DM A-pillar connector oxidised after water exposure, causing high resistance

✓
After driving through water, the SRS warning light stayed on. Retrieved DTC B170A1B; freeze frame data showed 4.2 Ω resistance. Removed the left A-pillar trim and found obvious water stains and white oxidation powder inside the curtain airbag harness connector (yellow). Cleaned the connector terminals and applied conductive protectant — resistance returned to 2.1 Ω and the fault cleared. Check the door seals and A-pillar drain holes for blockages.
BYD DTC AI Analysis

Left curtain airbag connector not fully seated after interior trim removal and refitting

✓
After removing the left A-pillar trim for audio system modification, the SRS warning lamp illuminated. Diagnosis showed current DTC B170A1B. Inspection found the curtain airbag connector was inserted, but the CPA (Connector Position Assurance) was not fully engaged, causing poor terminal contact. Reconnected the connector firmly until an audible click confirmed the lock, then used VDS to clear the fault codes. System returned to normal.
BYD DTC AI Analysis

Internal open circuit in clock spring causes intermittent warning

✓
The SRS warning light occasionally illuminated while driving, clearing after restarting. Diagnostics revealed intermittent DTC B170A1B with resistance fluctuating between 2.8 Ω and open circuit. Traced the left curtain airbag circuit through the clock spring (spiral cable) beneath the combination switch and identified an internal break in the flat ribbon cable. Replaced the clock spring and verified the repair by repeatedly turning the steering wheel; the fault did not return.
BYD DTC AI Analysis

Curtain airbag igniter body internal open circuit

✓
Vehicle repaired after collision. Replaced left curtain airbag but DTC B170A1B remained. Old airbag resistance: OL (open circuit); new airbag: 2.2 Ω (normal). Fault persisted after fitting. Further inspection found the crash crushed and deformed the wiring harness inside the B-pillar, partially fracturing internal copper wires and creating high resistance. Replacing the wiring harness resolved the fault.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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.