AU
B1792

DTC B1792 indicates the driver-side second-stage seat belt pretensioner circuit resistance falls below the normal range calibrated by the SRS ECU (typically 2 — Seal U

Safety System

DTC B1792 indicates the driver-side second-stage seat belt pretensioner circuit resistance falls below the normal range calibrated by the SRS ECU (typically 2.0-3.0Ω).

The second-stage pretensioner features a seat belt retractor with a dual-stage igniter that deploys in stages based on collision severity.

A low resistance value (<1.5Ω or close to 0Ω) indicates abnormal conduction resulting from an internal short circuit in the pretensioner igniter, a wiring harness short to ground, or connector water ingress and oxidation.

This fault forces the SRS system into fail-safe mode, disabling the pretensioner and associated airbag functions.

In extreme cases, the pretensioner may deploy without a collision or fail to operate during a collision, severely compromising the occupant restraint system's protection performance.

4
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Seat belt pretensioner internal igniter short circuit: Moisture ingress, aging, or manufacturing defects in the pretensioner cause the internal bridge wire to short to the housing, resulting in an abnormally low resistance value.
  • 2Wiring harness connector fault: Water ingress, oxidation, or deformed/loose pins at the K71 connector under the seat (pins 17/18) causing a signal wire short to ground or abnormal contact resistance.
  • 3Seat movement interference: Frequent seat adjustment chafes the pretensioner wiring harness at the slide rail, wearing through the insulation and shorting the core wire to body ground.
  • 4SRS ECU detection circuit fault: Faulty internal A/D conversion circuit or sampling resistor in the airbag control module causes a false low resistance reading (rule out via cross-check).
  • 5Improper repair after an accident: Pretensioner deployed during a collision but not replaced, or incorrectly measuring with a multimeter high-current setting during repair caused a partial short circuit in the igniter.
What To Do
  • 1
    Safe power-down: Turn the power switch to OFF, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental deployment.
  • 2
    Fault confirmation: Connect the VDS or dedicated diagnostic tool, read the SRS system fault codes, confirm B1792 is a current fault and not a history fault, and record the freeze frame data.
  • 3
    Visual inspection: Check the driver seat belt pretensioner for impact deformation or water marks. Check connector K71 for looseness and inspect the pins for oxidation or deformation.
  • 4
    Resistance measurement: Disconnect connector K71. Use a high-precision multimeter to measure the pretensioner-side resistance (standard value: 2.0–3.0 Ω). If <1.5 Ω, replace the pretensioner assembly. Measure the harness-side resistance to ground (should be >1 MΩ). If abnormal, inspect the harness for a short circuit.
  • 5
    Harness continuity test: Measure continuity of KJ10-1 (Y/L wire) and KJ10-2 (B/Y wire) between the ECU and the pretensioner (<1Ω). Check insulation to body ground and power supply.
  • 6
    Replacement verification: If pretensioner resistance is normal, install a known-good pretensioner and test. If the fault code clears, this confirms an internal fault in the original pretensioner.
  • 7
    Repair and Verification: After repairing or replacing the faulty component, reconnect all connectors. Turn the power to ON and wait 20 seconds for the system self-check. Confirm the fault code clears and the airbag warning light turns off. Perform a seat forward and backward movement test to verify no intermittent faults occur.
Real-World Cases
BYD DTC AI Analysis

BYD Qin seatbelt pretensioner internal short circuit

✓
The instrument cluster airbag warning light stayed on. Retrieved DTC B1792-00. Disconnected the K71 connector and measured the driver's pretensioner resistance at only 0.8Ω (standard 2-3Ω), indicating an internal igniter short. Found water stains at the pretensioner mounting bracket from a previous sunroof leak; determined prolonged moisture exposure caused the internal short. Replaced the driver's seatbelt pretensioner assembly, cleared the sunroof drain blockage, and erased the fault codes. System returned to normal.
Original source ↗
BYD DTC AI Analysis

BYD Surui seat wiring harness poor contact

✓
Airbag warning light intermittent; DTC B1792 intermittent. Found the K71 connector under the driver's seat loose with visible pin oxidation. Measured pretensioner resistance—normal, but shaking the seat caused fluctuations and intermittent shorts. Frequent seat adjustments had dislodged the harness retaining clip, letting the seat rail interfere with the wiring. Cleaned the pin oxidation, applied conductive grease, re-secured the harness routing, and fitted anti-abrasion sleeving. Fault resolved.
BYD DTC AI Analysis

BYD G6 pretensioner fault after accident repair

✓
Front collision repairs left the SRS warning light on with stored codes B1792 and crash sensor fault. The driver's seatbelt pretensioner had deployed in the accident but was never replaced; the repairer only reset it. Resistance across the pretensioner measured infinite (open circuit), but the connector pins had deformed during repairs, shorting the signal wire to ground (false short). The ECU flagged the low resistance first. Replaced the pretensioner assembly, repaired the connector pins, and recalibrated the SRS ECU. Fault cleared.
BYD DTC AI Analysis

Water wading caused pretensioner short circuit in BYD Song MAX

✓
After 3 years, the airbag warning light suddenly lit up. No collision history. DTC B1792. Measured pretensioner resistance at 0.5Ω, significantly below spec. Found water ingress marks on the driver's side carpet and green corrosion inside the pretensioner connector. Traced the issue to a detached AC drain hose causing condensation buildup. Replaced the pretensioner assembly, cleaned the connector, repaired the AC drain hose, and dried and waterproofed the wiring harness. Fault resolved.
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.