AU
B1792-00

This fault code indicates the driver-side second stage seat belt pretensioner ignition circuit resistance falls below the normal threshold set by the SRS control unit (ACU) (typically 2 — Atto 8

Safety System

This fault code indicates the driver-side second stage seat belt pretensioner ignition circuit resistance falls below the normal threshold set by the SRS control unit (ACU) (typically 2.0-4.0Ω; actual detected value below 1.5Ω or close to 0Ω).

The second stage pretensioner is part of the dual-stage gas generator system, providing progressive restraint force during a severe collision.

Low resistance typically indicates an internal squib short circuit, a wiring harness short to ground, or internal connector bridging.

This fault causes the ACU to disable the pretensioner function.

In extreme cases, the pretensioner may fail to deploy during a collision, or false fault detection during driving may continuously illuminate the SRS warning light, compromising the overall occupant restraint system protection strategy.

The B1792-00 fault code on the Atto 8 indicates low resistance in the driver-side second stage seat belt pretensioner ignition circuit. Severity is medium because the SRS control unit may disable the pretensioner, reducing restraint protection in a crash. Common causes include an internal pretensioner squib short or water ingress, corrosion, or damaged pins in the wiring connector. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
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Cases Logged
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Causes
Likely Causes — Atto 8
  • 1Pretensioner squib internal short circuit: Long-term exposure to heat and humidity, manufacturing defects, or chemical corrosion dampens the igniter charge, reducing insulation resistance between the terminals.
  • 2Wiring harness connector fault: Water ingress at connectors under the driver's seat or near the B-pillar, bent/backed-out pins, terminal bridging, or corrosion, causing the signal wire to short to ground or power.
  • 3Mechanical damage: Repeated chafing from the seat rail adjustment mechanism, improper seat removal or installation, or crushing by a foreign object damages the pretensioner wiring harness insulation, causing a short to ground.
  • 4Seat belt retractor assembly fault: internal short circuit in the pretensioner body, or retractor metal parts contacting the ignition terminal to form a low-resistance path.
  • 5ACU detection circuit misjudgment: A fault in the airbag control unit internal sampling resistor or A/D conversion circuit causes misreading of normal resistance values (less common but requires inspection).
What To Do
  • 1
    Safety preparation: Disconnect the battery negative terminal and wait at least 3 minutes for the SRS backup power supply to fully discharge to prevent accidental airbag deployment.
  • 2
    Initial diagnosis: Use BYD VDS or Launch X431 to read all DTCs and freeze frame data. Confirm if B1792-00 is a current code or history code, and check for other SRS-related fault codes.
  • 3
    Circuit isolation: Remove the driver-side B-pillar trim, locate the seat belt pretensioner connector (usually a yellow waterproof plug), and disconnect it to isolate the pretensioner from the wiring harness.
  • 4
    Resistance measurement: Use a digital multimeter (low current range, <1mA) to measure the resistance directly between the pretensioner body terminals. The standard value is 2.0-4.0 Ω. If the value is below 1.5 Ω or close to 0 Ω, the pretensioner body has a short circuit. Replace the seat belt retractor assembly.
  • 5
    Wiring harness inspection: Measure the resistance from the harness-side connector terminals to ground (should be >10MΩ) and the resistance between terminals (should be open circuit). Check for a short to ground or a short between wires. Carefully inspect the wiring harness insulation near the seat rail for wear.
  • 6
    Connector inspection: Check connector pins for push-out, bending, or green corrosion. Clean with electrical contact cleaner and verify the locking tab is intact. If the connector shows signs of water ingress, identify the source (e.g., poor window sealing).
  • 7
    ACU verification: If the pretensioner and wiring harness are normal, check the ACU connector pins for oxidation and measure continuity between the ACU and the pretensioner. If necessary, use an oscilloscope to check the ACU output detection pulse waveform.
  • 8
    Repair verification: After replacing the faulty component, reconnect all connectors, restore battery power, and clear the fault code. Perform the SRS system self-check cycle (cycle the ignition switch ON-OFF three times). Confirm the fault code does not return and the SRS warning light turns off normally.
Real-World Cases
BYD DTC AI Analysis

Qin EV300 pretensioner shorted after driving through water

✓
A 2017 BYD Qin EV300 came in with the SRS warning light on after driving through flood water. Retrieved DTC B1792-00. Found water in the wiring harness connector beneath the driver's seat; resistance between the pretensioner terminals measured 0.8Ω. Disassembly revealed the connector seal had deteriorated, allowing water ingress that caused a micro-short between the terminals. Repair: Replaced the seat belt retractor assembly (pretensioner had shorted and failed), fitted a new waterproof connector with insulation treatment, and cleared the drainage holes beneath the seat. Fault cleared.
BYD DTC AI Analysis

Seat modification damaged the wiring harness

✓
One week after installing racing seats in their 2018 BYD Qin EV450, the owner saw DTC B1792-00. The technician found the pretensioner harness unsecured during the modification. The seat rail bracket had pinched the harness repeatedly, wearing through the insulation and shorting the core wire to ground. Repair: Cut out the damaged section, soldered the joint and insulated it with heat-shrink tubing. Re-secured the harness along the standard routing path with adequate clearance from moving parts. Cleared the code; operation normal.
BYD DTC AI Analysis

Pretensioner internal resistance drift due to ageing

✓
2017 Qin 100, 120,000 km. Intermittent DTC B1792-00: present when cold, clearing when hot. Pretensioner resistance dropped to 1.2Ω in cold conditions, returning to 2.5Ω when warm. Diagnosis: Moisture ingress and aging of the internal igniter propellant caused abnormal temperature coefficient. Fix: Replaced OEM driver's side seat belt retractor assembly. Fault eliminated. Note: Verify soft faults with multiple measurements across different temperature environments.
BYD DTC AI Analysis

Connector pin backed out causing short circuit

✓
Following accident repairs, the vehicle set DTC B1792-00. Inspection found the B-pillar pretensioner connector had been misaligned during reinstallation, causing one terminal to back out and bend, contacting the adjacent terminal and creating a short circuit. Repaired the pin, reinstalled it using a dedicated terminal removal tool, applied conductive paste to ensure good contact, and relocked the connector. Fault cleared.
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.