AU
B1796-00

DTC B1796-00 indicates a short to ground in the control circuit of the driver-side second-stage seat belt pretensioner — Seal 6 EV

Safety System

DTC B1796-00 indicates a short to ground in the control circuit of the driver-side second-stage seat belt pretensioner.

The second-stage pretensioner is a dual-stage ignition component of the Supplemental Restraint System (SRS).

During a severe collision, a pyrotechnic device rapidly tightens the seat belt to eliminate slack between the occupant and the belt. "Short to ground" indicates an insulation failure between the pretensioner drive harness (typically the positive control wire) and the vehicle body ground (GND), causing resistance to drop abnormally (<1Ω).

This fault causes the SRS control unit (ACM) to detect abnormal circuit current, trigger fail-safe mode, and disable the pretensioner.

In extreme cases, this prevents the seat belt from tightening properly during a collision or creates a risk of unintended deployment under specific conditions.

4
Cases Logged
5
Causes
Likely Causes — Seal 6 EV
  • 1Wiring harness abrasion inside the B-pillar trim panel: As the driver's seat belt pretensioner wiring harness routes under the B-pillar, long-term seat adjustment or vibration from opening and closing the door causes metal edges to cut the insulation, resulting in a short to ground.
  • 2Under-seat connector corrosion: Vehicle wading, improper interior cleaning, or a blocked sunroof drain tube allows water to flow under the seat. This oxidizes and electrolytically corrodes the pretensioner connector (yellow) terminals, forming a short-to-ground path.
  • 3Pretensioner body internal short circuit: Moisture in the second-stage igniter pyrotechnic charge or a manufacturing defect causes insulation failure between the ignition wire and the metal housing.
  • 4SRS control unit internal drive circuit fault: Breakdown of the ACM internal ignition drive chip causes the output terminal to short to ground, resulting in a false pretensioner fault.
  • 5Improper modification or accident repair: Removing and installing the seat belt assembly during seat heater installation, racing seat modification, or accident repair crushes the wiring harness or dislodges the retaining clips, causing the wiring harness to contact vehicle body metal.
What To Do
  • 1
    Safe power-down: Turn off the ignition, disconnect the battery negative terminal, and wait at least 3 minutes to fully discharge the SRS system capacitor and prevent accidental pretensioner deployment.
  • 2
    Visual inspection: Remove the driver-side B-pillar lower trim panel and under-seat guard panel. Inspect the pretensioner wiring harness (yellow corrugated conduit) for wear, cuts, or burn marks. Focus on contact points between the wiring harness and body sheet metal.
  • 3
    Connector diagnosis: Disconnect the pretensioner connector (usually located under the seat or at the base of the B-pillar). Check the terminals for green oxidation, water stains, or burn marks. Clean with compressed air and apply electronic contact protectant if necessary.
  • 4
    Resistance measurement: Use a multimeter to measure the pretensioner body resistance (connector side). The normal value is 1.8-3.2 Ω. Measure the harness-side insulation resistance to ground; it must be greater than 1 MΩ. A resistance of <1 Ω indicates a short circuit.
  • 5
    Wiring harness repair: If the wiring harness is damaged, strip the insulation, repair the wire with solder, apply double-layer heat-shrink tubing for insulation protection, and re-secure the wiring harness routing. Maintain a clearance of more than 20mm from the vehicle body.
  • 6
    Component replacement: If the pretensioner has an internal short circuit (abnormal resistance with a normal wiring harness), replace the driver-side seat belt assembly (including the pretensioner). Note: The pretensioner is an explosive component. Handle the old part according to dangerous goods transport regulations.
  • 7
    System reset: Connect the battery, use the diagnostic tool to clear the fault code, and perform 'SRS System Configuration' or 'ECU Re-coding' (if replacing the control unit). Finally, perform an ignition switch cycle test to confirm the fault code does not recur.
Real-World Cases
BYD DTC AI Analysis

B-pillar wiring harness chafing caused intermittent short circuit on Qin EV300

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**Symptoms:** Airbag warning light comes on intermittently on rough roads, goes off on smooth surfaces. Intermittent DTC B1796-00. Owner reported recent seat height adjustment. **Diagnosis:** Removed B-pillar lower trim panel. Found driver seatbelt pretensioner harness (yellow) had chafed through insulation at seat rail mounting bracket, with copper conductor contacting chassis ground. Resistance fluctuated between 0.2Ω and 5Ω during vehicle vibration. **Resolution:** Repaired damaged harness (soldered, double-layer heat shrink tubing), adjusted harness routing and added rubber protective sleeve, re-secured to harness bracket. Fault resolved.
BYD DTC AI Analysis

Qin 100 pretensioner connector corroded after water ingress

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**Symptoms:** After driving through deep water, the airbag warning light remained on constantly. Scanned DTC B1796-00. Found the carpet under the driver's seat was wet. **Diagnosis:** Removed the seat. The pretensioner connector (yellow 2-pin) had obvious water stains and green corrosion inside, with insulation resistance between terminals down to 0.8Ω. The sunroof drain tube had detached, allowing rainwater to run down the A-pillar and pool beneath the seat. **Resolution:** Thoroughly dried the seat and wiring harness. Cleaned the connector terminals with precision instrument cleaner, blew them dry, then applied dielectric grease. Repaired the drain tube. Cleared the fault code; it did not return.
BYD DTC AI Analysis

Qin EV450 second-stage pretensioner internal short circuit

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**Symptoms:** No collision history. Airbag warning light stays on after normal startup. DTC B1796-00 stored and will not clear. **Diagnosis:** Disconnected the pretensioner plug under the seat. Measured >10MΩ insulation to earth on the harness side (normal). Measured 0.3Ω across the pretensioner itself (specification ~2.0Ω). Determined the second-stage igniter has an internal short to housing. **Repair:** Replaced the driver-side seat belt assembly (Part No. BYD-5820XXXX). Post-repair resistance measured 2.1Ω. Cleared the DTC; system self-test passed. Processed the old component per explosive material recycling procedure.
BYD DTC AI Analysis

Seat modification pinched the pretensioner harness, causing a short circuit.

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**Symptoms:** After installing racing seats, the airbag warning light came on while driving with DTC B1796-00. The shop had removed the factory seatbelt buckles. **Diagnosis:** The aftermarket seat bracket was crushing the factory pretensioner wiring harness, damaging the insulation and shorting it to the bracket (chassis ground). Resistance at the short: 0.1Ω. **Resolution:** Removed the aftermarket seats and repaired the harness (cut and re-spliced due to severe damage). Re-routed the wiring to clear the seat rail travel path and added a harness protection plate. Fault cleared. Advised the owner to use pretensioner-compatible seats or retain the factory seatbelt system for any future modifications.
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.