AU
B175C-00

DTC B175C-00 indicates the airbag control unit (SRS ECU) detects resistance in the Right Rear Side Airbag ignition circuit above the calibrated threshold — Seal U

Safety System

DTC B175C-00 indicates the airbag control unit (SRS ECU) detects resistance in the Right Rear Side Airbag ignition circuit above the calibrated threshold.

Normal airbag igniter resistance ranges from 1.6Ω to 2.4Ω (standard value approximately 2.0Ω).

The ECU sets this fault when it detects resistance exceeding approximately 2.8Ω or a high-resistance state in the circuit.

This fault indicates poor contact or a partial open in the ignition circuit, or abnormal internal resistance in the airbag module.

As a functional fault in the passive safety system, it may prevent the side airbag from deploying during a collision.

Because the SRS uses a two-stage diagnostic mechanism, this fault code continuously illuminates the airbag warning lamp and may force the entire airbag system into a downgraded protection mode, even if the vehicle remains drivable.

3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Right rear seat side airbag wiring harness connector loose or oxidized: Frequent seat movement or damp environments increase contact resistance at the connector pins. This is the most common cause of the fault.
  • 2Airbag wiring harness worn or internally broken: Repeated harness bending at the seat rail, B-pillar, or sill trim panel partially breaks the copper wire without causing a complete open circuit, resulting in abnormally high resistance.
  • 3Airbag igniter internal fault: The ignition resistance wire inside the airbag module is aged or poorly connected, causing the resistance value to fall outside the normal range.
  • 4SRS ECU internal detection circuit fault: A faulty sampling resistor or detection circuit inside the control unit incorrectly detects the airbag resistance as too high.
  • 5Water ingress or liquid corrosion: After the vehicle drives through water, water enters the wiring harness connectors below the right B-pillar or under the seat, causing pin oxidation and corrosion that creates contact resistance.
What To Do
  • 1
    Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes to discharge the SRS capacitor residual charge to prevent accidental airbag deployment. Wear an anti-static wrist strap. Do not measure the airbag directly with a standard multimeter. Use a dedicated airbag tester or a multimeter with a current limit below 10mA.
  • 2
    Visual inspection: Remove the right rear sill trim panel and seat side trim panel. Inspect the airbag wiring harness for wear, crushing, or water marks. Specifically check the under-seat connector for looseness and the locking tab for breakage.
  • 3
    Connector handling: Disconnect the airbag module connector (usually a yellow plug) and check the terminals for oxidation, backed-out pins, or deformation. Clean with electronic contact cleaner, apply conductive grease, and ensure the locking mechanism is intact.
  • 4
    Resistance measurement: Use a low-current ohmmeter to measure the resistance between the two terminals of the airbag module. Normal resistance is 2.0Ω±0.4Ω. If the resistance exceeds 2.8Ω, replace the airbag module. If the resistance is normal, continue checking the wiring harness.
  • 5
    Harness continuity test: Disconnect the SRS ECU connector and the airbag connector. Measure the resistance between the airbag harness terminal and the corresponding ECU terminal. Resistance must be less than 1Ω. Measure the insulation resistance from the harness to ground and to the power supply. Resistance must be greater than 1MΩ to rule out a short circuit.
  • 6
    Replacement verification: Perform a substitution test using a known-good airbag module or a dedicated airbag simulator (2Ω resistor). Clear the fault code, set the power mode to ON, wait 20 seconds, and read the fault code. If the fault disappears, the original airbag module is faulty. If the fault remains, check the wiring harness or replace the SRS ECU.
  • 7
    Repair and verification: After repairing or replacing the faulty wiring harness/connector, reconnect all components and clear the fault code. Perform multiple ignition cycle tests and a road test to confirm the fault light does not illuminate. Use a diagnostic tool to read the SRS data stream and confirm the right rear side airbag resistance value is within the normal range.
Real-World Cases
BYD DTC AI Analysis

BYD Qin Pro right rear side airbag connector oxidized, causing high resistance

✓
Symptom: Airbag warning light stays on. Scanner shows DTC B175C-00. No collision history; fault appeared suddenly. Diagnosis: Disconnected the battery and checked the right rear seat side airbag connector. Measured airbag harness terminal resistance to ground: >1MΩ (normal). Voltage to ground: <1V (normal). Measured resistance between K08-2 (Y/B) and K71-17 (harness between airbag module and ECU): >1Ω (abnormal). Found the harness connector inside the right rear sill trim oxidised and loose. Fix: Cleaned the oxidised terminals and applied conductive grease. Re-secured the connector. Cleared the fault codes and cycled the ignition multiple times. Fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD Song Pro DM rear side airbag wiring harness chafing causing intermittent warning

✓
Symptom: Airbag warning light illuminates intermittently, particularly over rough surfaces. Stored DTC: B175C-00. Diagnosis: Found the RH rear seat side airbag connector not fully locked. Reconnected and cleared the DTC, but the fault returned two days later. Further inspection revealed chafing damage to the harness at the seat rail, causing intermittent high resistance. Measuring resistance at the airbag module while moving the harness showed fluctuation between 2.8Ω and 5.2Ω (specification: 2Ω±0.4Ω). Resolution: Replaced the RH rear seat side airbag wiring harness assembly. Adjusted the harness routing to avoid the seat rail and secured it with cable ties, ensuring adequate movement allowance. Cleared the DTCs and road tested; no recurrence.
Original source ↗
BYD DTC AI Analysis

Replaced right rear side airbag on BYD Tang II; fault persists

✓
Symptoms: Airbag warning light stayed on with DTC B175C-00 after right rear door body repair and removal of right rear seat. Shop replaced right rear side airbag module but fault remained. Diagnosis: New airbag module resistance measured 2.1Ω (normal). Checked harness between airbag ECU and module: K08-1 (Y/R) to K71-18 measured 0.8Ω (normal), but K08-2 (Y/B) to K71-17 measured 3.5Ω (high). Found right B-pillar lower connector had water ingress during previous repair, causing pin oxidation. Resolution: Replaced right B-pillar lower SRS harness connector, dried harness and applied waterproof sealant. Reconnected, cleared codes, and cycled ignition multiple times to confirm fix.
Original source ↗
Other Seal U 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.