AU
B1793

This DTC indicates the Airbag Control Module (ACM) detects the driver-side second-stage seatbelt pretensioner circuit resistance exceeds the calibrated range (typically 2-5 ohms) — Atto 8

Safety System

This DTC indicates the Airbag Control Module (ACM) detects the driver-side second-stage seatbelt pretensioner circuit resistance exceeds the calibrated range (typically 2-5 ohms).

This Passive Safety System (SRS) circuit fault indicates high resistance or an open circuit in the pretensioner circuit.

The pretensioner is a critical protective device that uses a pyrotechnic charge to instantly tighten the seatbelt during a collision.

This fault indicates the driver-side seatbelt may fail to pretension correctly during a frontal collision, increasing occupant forward travel, reducing restraint system effectiveness, and posing a severe safety hazard.

The B1793 fault code on the Atto 8 indicates a medium-severity SRS fault where the driver-side second-stage seatbelt pretensioner circuit has resistance above the expected range. This may be caused by an open or aging pretensioner coil, or a loose, corroded, or water-damaged connector under the seat. The vehicle should be inspected and repaired by an authorised dealer. Typical repair cost data is available from recorded cases.
3
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Open circuit, aging, or increased resistance in the driver seat belt pretensioner internal coil.
  • 2Loose connection, backed-out pins, oxidation, or water ingress at the pretensioner wiring harness connector (yellow plug) under the seat, causing increased contact resistance.
  • 3Prolonged bending and wear of the pretensioner wiring harness at the seat slide rail causes internal wire breakage or a partial open circuit.
  • 4Vehicle wading or high humidity causes corrosion on the pretensioner connector terminals, forming an oxide layer that increases resistance.
  • 5Airbag Control Module (ACM) internal sampling circuit fault or software calibration error (less common)
What To Do
  • 1
    Use the dedicated diagnostic tool to read the fault code, confirm if B1793 is an Active or History fault, and record the resistance value from the freeze frame data.
  • 2
    Disconnect the battery negative terminal and wait at least 90 seconds for the airbag system capacitor to fully discharge (observe safety operating procedures).
  • 3
    Check the airbag wiring harness connector under the driver’s seat (yellow-marked plug) for looseness, backed-out pins, oxidation, or signs of water ingress. Clean the terminals with electrical contact cleaner, apply conductive grease, and reconnect.
  • 4
    Remove the driver's seat and carefully inspect the pretensioner wiring harness insulation for wear at the seat slide rail bend. Measure the continuity and resistance of the wiring harness between the connector and the pretensioner.
  • 5
    Disconnect the pretensioner connector and use a multimeter to measure the resistance of the pretensioner unit (normal range: 2-5 Ω). If the resistance is infinite or >5 Ω, the pretensioner unit is faulty. Replace the driver seat belt pretensioner assembly.
  • 6
    Measure wiring harness continuity between the pretensioner connector and the Airbag Control Module (ACM), focusing on the floor harness junction points. Repair high resistance or open circuits. Replace the wiring harness if necessary.
  • 7
    Reinstall the seat and all connectors. Ensure the wiring harness does not interfere throughout the full travel of the seat slide rails. Connect the battery, clear the fault codes, and perform a system self-check (turn the ignition switch to the ON position and verify the SRS warning light turns off normally).
  • 8
    Perform a road test or simulate seat forward and backward movement and vibration to confirm the fault code does not recur and the system returns to normal operation.
Real-World Cases
BYD DTC AI Analysis

BYD Song MAX: Loose connection in wiring harness under seat caused SRS fault.

✓
Symptoms: Airbag warning light stays illuminated. Scanned and retrieved restraint system fault codes. Vehicle has no collision history; warning light remains on. Diagnosis: Checked wiring harness connector under driver's seat. Found loose connection with oxidized pins; measured contact resistance >10Ω. Inspected wiring at seat rails; no mechanical damage. Repair: Cleaned and re-secured seat harness connector, sanded terminals to remove oxidation, applied conductive grease to prevent further oxidation, cleared fault codes. Warning light extinguished; system returned to normal.
BYD DTC AI Analysis

BYD F3 Seat Belt Buckle Switch Circuit Fault (similar to B2692 case)

✓
Symptoms: Airbag warning light illuminates intermittently after startup with beeping alarm. No obvious correlation with driver seatbelt use; occurs occasionally on rough roads. Diagnosis: Scan tool retrieved seatbelt buckle switch circuit fault from airbag system. Wiring harness beneath driver seatbelt buckle showed internal conductor breakage from long-term flexing. Seatbelt buckle switch had intermittent contact. Resolution: Replaced driver seatbelt buckle assembly (with switch), repaired broken harness and added protective sleeve. Cleared codes with scan tool; road test confirmed warning light and alarm no longer occur.
Original source ↗
BYD DTC AI Analysis

BYD Tang: Water ingress in seat belt pretensioner connector caused corrosion and high resistance.

✓
Symptoms: Airbag warning light stayed on after driving through water. Scan tool retrieved DTC B1793 for high resistance in the driver's second-stage seatbelt pretensioner. Diagnosis: Removed the driver's seat and found the pretensioner connector (yellow waterproof plug) had water staining and green copper corrosion inside. The pretensioner body measured 3.2Ω (normal), but resistance through the harness read infinite with the connector attached. Corroded terminals were causing an open circuit. Repair: Replaced the connector terminals, dried and resealed the plug, applied conductive grease, and reconnected. Cleared the codes and the system returned to normal. Recommendation: Inspect the floor sealing strips to prevent water ingress.
Other Atto 8 Fault Codes
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.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.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.