UAE
AU
B1791-00

DTC B1791-00 indicates the driver-side Stage 2 Seatbelt Pretensioner resistance measures 0 ohms — Atto 3

Safety System

DTC B1791-00 indicates the driver-side Stage 2 Seatbelt Pretensioner resistance measures 0 ohms.

Normal pretensioner igniter resistance is 2.0-4.0 ohms.

A 0-ohm reading indicates a circuit Short to Ground or an internal short in the pretensioner squib.

This fault prevents the SRS control unit from triggering the Stage 2 Seatbelt Pretensioner during a collision (typically used for secondary tightening in severe impacts), compromising occupant restraint system effectiveness.

Additionally, the SRS warning lamp remains illuminated, the system enters fail-safe mode, and the airbags may fail to deploy.

4
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Qin EV450 seat movement caused wiring harness chafing and short circuit

✓
SRS warning light stayed on when the vehicle came in. Retrieved DTC B1791-00. Found the driver frequently adjusted the seat position, causing the seat rail edge to cut through the yellow SRS harness sleeve underneath. Exposed wires contacted the body and shorted to ground. Repair: Fixed the damaged harness (3 wires with damaged insulation, 1 completely severed), re-wrapped it with corrugated tubing, rerouted the harness, and added clips to prevent interference with the seat rails. Fault cleared after repair; no recurrence after 3 months of follow-up.
BYD DTC AI Analysis

Qin 80 pretensioner connector corroded after driving through water

✓
Customer reported the SRS warning light illuminated after heavy rain. DTC B1791-00 stored. Inspection confirmed water ingress; the carpet beneath the driver's B-pillar was damp. The pretensioner connector (D21) showed visible water stains and green oxidation. Resistance between pins measured 0.5Ω (short circuit). Diagnosis: Disassembled the connector and found the seal degraded. Cleaning the pins revealed electrolytic corrosion between pin 2 (ground) and pin 3 (signal) that created a micro-short. Repair: Replaced the connector assembly, treated the water-damaged harness section, applied waterproof silicone grease to the connector, and cleared the fault.
BYD DTC AI Analysis

Replaced rear seat belt pretensioner due to internal short circuit

✓
After accident repairs, the SRS warning light illuminated with DTC B1791-00. Service history showed the driver's seat belt assembly had just been replaced. The new pretensioner resistance measured 0.2Ω (abnormal); the old component measured 2.3Ω (normal) after disassembly. Root cause: The technician did not disconnect the battery during replacement. A wrench touched the pretensioner connector, causing momentary high current that burned out the pretensioner squib and created an internal short. Solution: Replaced the seat belt assembly under warranty and strictly followed SRS repair safety procedures (disconnect battery negative terminal first). Fault resolved.
BYD DTC AI Analysis

SRS ECU incorrectly detecting zero resistance

✓
Intermittent SRS warning light, DTC B1791-00. Static measurement showed pretensioner resistance of 2.8Ω (normal). Wiring harness insulation to ground tested good. Fault reoccurred on rough roads. Found loose connection at SRS ECU connector (inside dashboard) pin D21 (pretensioner signal). Oxidation caused unstable contact resistance; vibration triggered abnormal voltage sampling and the ECU misread it as 0Ω. Fix: Cleaned ECU connector pins, adjusted pin tension, applied conductive grease. No recurrence.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
Data confidence: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.