AU
B1796

This DTC indicates a short to body ground in the driver-side second-stage seat belt pretensioner deployment circuit — Seal 6 EV

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 Seal 6 EV indicates a high-severity short to body ground in the driver-side second-stage seat belt pretensioner circuit. This can disable extra seat belt tightening in a severe crash and may increase injury risk. Common causes include worn SRS wiring under the driver’s seat or water/corrosion in 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 — Seal 6 EV
  • 1Wiring harness wear under the seat: Long-term repeated movement of the driver's seat fore-and-aft adjustment mechanism wears through the floor wiring harness insulation (especially the SRS harness routed beneath 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, a poorly sealed pretensioner connector below the B-pillar or under the seat allows internal pins to oxidize and short to ground.
  • 3Pretensioner internal short circuit: The squib inside the second-stage pretensioner shorts directly to the metal housing due to a manufacturing defect or long-term vibration causing internal coil insulation failure.
  • 4SRS wiring harness pierced by foreign object: 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 repair: Sharp sheet metal edges cut an improperly secured wiring harness, or a partially seated pretensioner connector causes the terminal to contact the vehicle body.
What To Do
  • 1
    Safety Preparation and Power-Down: Verify the vehicle is in the OFF position, wear insulated gloves, disconnect the 12V battery negative terminal, and wait at least 90 seconds to allow the SRS capacitor to discharge fully. For hybrid/EV 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 the seat side trim panel to expose the second-stage seat belt pretensioner (usually integrated into the retractor assembly or at the base of the B-pillar). Identify the two-wire connector with the yellow protective 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. If the resistance from either pin to ground is <1 MΩ, confirm a short to ground.
  • 4
    Section-by-section harness inspection: If the pretensioner resistance is normal, strip back the corrugated conduit along the SRS wiring harness section by section 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. Inspect 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 shorts internally (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 and 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 return and the airbag warning light 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 Seal 6 EV 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.B1737DTC B1737 indicates the Supplemental Restraint System (SRS) detected abnormal continuity between the right middle-row side airbag squib circuit (typically the second-row right seat side airbag or right curtain airbag) and the vehicle power supply (B+, battery positive). The SRS ECU monitors the airbag inflator resistance via an internal current source (normal resistance: 2.0–3.0 Ω). If the ECU detects the voltage across the inflator circuit remaining close to battery voltage (>5 V and approaching 12 V) instead of the expected low potential or floating state, it identifies a short to power. This fault prevents the airbag from deploying normally during a collision because the short circuit bypasses the firing current. In extreme cases, abnormal current can cause unintended deployment, posing a severe safety hazard.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 Seal 6 EV →Seal 6 EV 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.