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B170A-00

DTC B170A-00 indicates the Supplemental Restraint System (SRS) detected the resistance in the left curtain shield airbag igniter circuit exceeds the calibrated threshold (normal range is typically 2 — Qin Plus

Safety System

DTC B170A-00 indicates the Supplemental Restraint System (SRS) detected the resistance in the left curtain shield airbag igniter circuit exceeds the calibrated threshold (normal range is typically 2.0-3.0Ω; fault threshold is generally >3.5Ω or open circuit).

The SRS ECU continuously monitors the circuit impedance of each airbag igniter using a low-current detection circuit.

Excessive resistance indicates a high-resistance condition in the circuit.

Potential causes include poor connector contact, a partially broken wiring harness, or increased internal resistance from igniter aging.

This fault prevents the left curtain shield airbag from deploying normally during a collision and constitutes a critical failure in the passive safety system.

The B170A-00 fault code on the Qin Plus indicates the SRS has detected excessive resistance or an open circuit in the left curtain shield airbag igniter circuit. This is a medium-severity safety fault that may stop the airbag from deploying in a crash. Common causes include a loose or oxidized igniter connector or a damaged wiring harness near the pillar/door hinge area. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Qin Plus
  • 1Loose or oxidized left curtain airbag igniter connector: Moisture or vibration increases contact resistance in the connector located inside the left C-pillar trim panel or on the left roof side rail.
  • 2Worn or broken wiring harness: Long-term bending from opening and closing the door partially breaks the copper wires where the left curtain airbag wiring harness passes through the left front door hinge, A-pillar, or B-pillar wiring holes (common failure area on Qin series models).
  • 3Clock spring (spiral cable) internal fault: If the vehicle steering wheel-to-body wiring harness includes the curtain airbag circuit, internal slip ring wear in the clock spring increases resistance.
  • 4Left curtain airbag unit fault: Increased internal resistance in the squib due to aging, moisture ingress, or manufacturing defects.
  • 5SRS ECU detection circuit fault: Abnormal components in the corresponding detection channel inside the airbag control unit cause a false high resistance reading.
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS backup power supply and prevent accidental airbag deployment.
  • 2
    Preliminary check: Use BYD VDS or Launch X431 to read the DTC freeze frame. Confirm the vehicle status and ambient temperature at the time of the fault to rule out intermittent interference.
  • 3
    Data stream analysis: Access the SRS system data stream and check the 'left curtain airbag resistance' value (normal is approximately 2.5Ω; a reading >4Ω or 'open circuit' confirms the fault).
  • 4
    Connector check: Remove the left C-pillar trim panel and left roof interior trim panel. Verify the left curtain airbag white/yellow connector is fully seated. Inspect the terminals for green oxidation or backed-out pins.
  • 5
    Harness continuity test: Disconnect the SRS ECU and left curtain airbag connectors. Use a multimeter to measure harness continuity between them. Check the bent section of the harness at the left front door hinge for open circuits or high resistance (should be <1Ω).
  • 6
    Component replacement verification: If the wiring harness is normal, remove the left curtain airbag and measure its igniter resistance (standard value: 2.0 ± 0.3 Ω). If the resistance is too high, replace the left curtain airbag assembly. If the curtain airbag is normal but the fault persists, check or replace the SRS ECU.
  • 7
    System reset: After repair, connect the battery. Use the diagnostic tool to clear the fault code and perform "Configuration and Settings". Perform the SRS system self-check. Confirm the resistance returns to normal and the warning light turns off.
Real-World Cases
BYD DTC AI Analysis

Qin EV450 left curtain airbag connector oxidised, causing high resistance

✓
A 2018 Qin EV450 with 30,000 km showed a constant SRS warning light. Scanned with VDS, retrieved DTC B170A-00 (left side curtain airbag resistance too high). Data stream showed resistance at 5.8Ω (out of spec). Removed the left C-pillar trim and found obvious green oxidation inside the left roof curtain airbag connector — caused by moisture ingress from a previous window tint installation. Cleaned the pins with electronic contact cleaner, applied conductive grease, and reconnected the connector. Resistance returned to 2.4Ω. Fault cleared.
BYD DTC AI Analysis

Qin 100 left front door hinge wiring harness worn through and broken.

✓
2017 BYD Qin 100 had B170A-00 DTC. Left side curtain airbag resistance showed 'open circuit'. Inspection found wiring harness insulation worn through at the left front door hinge (below A-pillar) from repeated door opening/closing, with internal copper conductors fractured down to only 2-3 strands remaining, creating high resistance. After stripping back the harness and locating the break, the copper cores were spliced using a dedicated crimping pliers, soldered, and sealed with heat-shrink tubing. The wiring was rerouted and additional anti-chafe sleeving added. Fault resolved. This is a common issue on Qin series vehicles.
BYD DTC AI Analysis

Replaced the aged curtain airbag igniter on the Qin EV300

✓
A 2017 Qin EV300 developed DTC B170A-00 following accident repairs. Wiring harness continuity tested normal. Direct measurement of the left curtain airbag showed a resistance of 8.5Ω, severely out of specification. Diagnosis determined the curtain airbag's internal igniter had sustained impact damage during the collision or had aged, causing increased internal resistance. Replaced the left curtain airbag assembly (part number: ...). Used VDS to perform ECU configuration coding, which requires entering the resistance value parameter from the new airbag label. Performed a system self-test, and the fault code cleared.
BYD DTC AI Analysis

Resolved false SRS ECU fault with software update

✓
Multiple 2017 BYD Qin 80s simultaneously set DTC B170A-00 and similar resistance-related fault codes. Measured the actual wiring resistance and curtain airbag resistance; both were within normal range. A BYD Technical Service Bulletin (TSB) confirmed that early batch SRS control unit software calibration was overly sensitive, causing false DTCs. Upgraded the SRS ECU software via VDS from V1.2 to V1.4. The fault codes cleared after the update and system monitoring returned to normal.
Other Qin Plus 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.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.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.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Qin Plus →Qin Plus 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.