AU
B1796

This DTC indicates a short to body ground in the driver-side second-stage seat belt pretensioner deployment circuit — Qin Plus

Safety System

This DTC indicates a short to body ground in the driver-side second-stage seat belt pretensioner deployment circuit.

The second-stage pretensioner is a pyrotechnic device in the SRS (Supplemental Restraint System).

It operates in series or parallel with the first-stage pretensioner to provide greater seat belt tightening force during a severe collision (high-speed frontal impact).

A short to ground occurs when damaged insulation on the positive wire from the SRS ECU to the pretensioner squib contacts the vehicle body metal, causing circuit resistance to drop abnormally (typically <1Ω).

The SRS ECU detects this abnormal current path, illuminates the airbag warning lamp, and disables the second-stage pretensioner function.

In a severe collision, the driver may lose second-stage protection, increasing the risk of injury.

In extreme cases, the short-circuit current can accidentally trigger the pretensioner, locking the seat belt and requiring costly replacement.

The B1796 fault code on the Qin Plus indicates a short to body ground in the driver-side second-stage seat belt pretensioner deployment circuit. This is a high-severity SRS fault because it can disable extra seat belt tightening in a severe crash, and may rarely trigger the pretensioner unexpectedly. Common causes include worn under-seat SRS wiring or water ingress and corrosion at the pretensioner connector. 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
  • 1Under-seat wiring harness wear: Long-term repeated movement of the driver seat fore-and-aft adjustment mechanism wears through the floor wiring harness insulation (especially the SRS harness routed under the seat slide rail), causing the copper wire to contact body ground.
  • 2Pretensioner connector water ingress and corrosion: When driving through water or cleaning the interior, poor sealing of the pretensioner connector below the B-pillar or under the seat causes internal pins to oxidize and short to ground.
  • 3Pretensioner internal short circuit: Manufacturing defects or long-term vibration cause internal coil insulation failure, shorting the second-stage pretensioner squib directly to the metal housing.
  • 4Foreign object piercing the SRS wiring harness: Metal objects (such as coins or screws) left under the seat pierce the SRS wiring harness sheath during seat movement, causing a short to ground.
  • 5Improper previous collision repairs: Sharp sheet metal edges cut an improperly secured wiring harness, or a partially seated pretensioner connector allows the terminal to contact the vehicle body.
What To Do
  • 1
    Safety preparation and power-down: Confirm the vehicle is in the OFF position. Put on insulated gloves. Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor. For hybrid/pure electric models, perform the high-voltage system power-down procedure first (disconnect the service plug).
  • 2
    Locate the faulty component: Remove the driver-side B-pillar lower trim panel and seat side trim panel to expose the second-stage seat belt pretensioner (usually integrated into the retractor assembly or the base of the B-pillar). Identify the two-wire connector with the yellow sleeve.
  • 3
    Disconnect and isolate: Disconnect the pretensioner connector. Use a multimeter to measure the resistance between the two pins on the pretensioner side (normal: 1.5-3.0 Ω). Measure the resistance from each pin to body ground separately. If the resistance from either pin to ground is <1 MΩ, this confirms a short to ground.
  • 4
    Inspect the wiring harness section by section: If the pretensioner resistance is normal, open the corrugated conduit section by section along the SRS harness from the pretensioner to the SRS ECU. Focus on the harness under the seat slide rail, inside the sill trim panel, and at the floor pass-through. Look for signs of abrasion, crushing, or corrosion.
  • 5
    Repair or replace: If the wiring harness is damaged, repair it using heat-shrink tubing or tape and re-secure it. Maintain a safe distance from the vehicle body. If the pretensioner has an internal short circuit (pin continuity to ground), replace the entire seat belt retractor assembly (including the pretensioner). Do not attempt to repair the pyrotechnic device.
  • 6
    System verification: Reconnect all connectors, reconnect the battery, use the BYD VDS diagnostic tool to clear the fault code, and run the 'SRS System Self-test' function. Confirm B1796 does not reappear and the airbag warning lamp turns off. Finally, move the seat forward and backward to confirm no wiring harness interference.
Real-World Cases
BYD DTC AI Analysis

Song MAX seat rail chafed through SRS harness, causing second-stage pretensioner short circuit

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2020 Song MAX. Instrument cluster intermittently displayed "Check Airbag System." VDS scan retrieved DTC B1796. Inspection found the floor harness sheath beneath the driver seat rail worn through by shear forces during seat adjustment, exposing two SRS wires. One wire shorted to the seat frame (chassis ground). The harness retaining clip had detached, letting the wiring drop into the seat track. Repaired the damaged harness by insulating each wire individually and sleeving with corrugated tubing, resecured it with zip ties above the seat frame, and fitted a new retaining clip. Fault resolved.
BYD DTC AI Analysis

Tang DM: Corroded B-pillar connector causes intermittent short circuit after water ingress

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2021 BYD Tang DM. After wading through floodwater during heavy rain, the airbag warning light stayed on with DTC B1796. Inspection found mud and water inside the second-stage pretensioner connector below the driver's side B-pillar. The pins had oxidised, producing verdigris that caused unstable resistance between the positive terminal and the connector metal housing (ground) — normal when cold, shorting to ground when hot. Cause: wading depth exceeded the sill seal height. Repair: Cleaned the connector thoroughly with electronic cleaner, dried it with compressed air, applied conductive anti-corrosion compound, and installed a new waterproof connector housing. Fault resolved.
BYD DTC AI Analysis

Yuan EV: Unsecured pretensioner wiring harness following accident repair caused short circuit

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A 2019 Yuan EV logged DTC B1796 one month after front collision repairs. Records showed the driver's seat belt assembly was replaced after the accident, but the pretensioner harness wasn't routed to factory specs. The seat adjustment mechanism pinched the harness, damaging the insulation and causing a short to body. Fix: Rerouted the wiring per workshop manual standards, secured the SRS harness clear of moving components using OEM retaining clips, repaired the damaged conductors, cleared the DTC and verified.
BYD DTC AI Analysis

Qin Pro pretensioner internal igniter short circuit false positive

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2020 Qin Pro, no collision history, but VDS reports B1796 which will not clear. Disconnected the driver's second-stage pretensioner connector: measured infinite resistance to ground on the harness side (normal), but 0.2Ω between the pretensioner (retractor assembly) pins and metal housing. Confirms the internal pyrotechnic device is shorted to the housing. Supplier batch quality issue. Fix: Replace the driver's side seatbelt retractor assembly (part number must match the VIN to ensure correct trigger level), use VDS to perform the 'replacement component coding' procedure to match the new pretensioner to the SRS ECU. Fault resolved.
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.