NO
AU
B1799-00

DTC B1799-00 indicates the SRS (Supplemental Restraint System) ECU detects the front passenger-side second-stage seat belt pretensioner circuit resistance exceeds the normal upper limit (typically >3 — Atto 3

Safety System

DTC B1799-00 indicates the SRS (Supplemental Restraint System) ECU detects the front passenger-side second-stage seat belt pretensioner circuit resistance exceeds the normal upper limit (typically >3.0-3.5Ω, normal range is 2.0-3.0Ω).

The second-stage pretensioner is a critical component of the airbag system.

During a severe collision, a pyrotechnic charge generates a rapid tightening force, working with the first-stage pretensioner to provide enhanced occupant restraint.

Excessive resistance typically indicates a high-resistance circuit contact, a partial open circuit, or an aging internal resistance wire within the pretensioner.

This causes the ECU to identify a pretensioner failure risk, illuminate the airbag warning light, and potentially disable the front passenger-side airbag and pretensioner functions.

During a collision, the second-stage pretensioner may fail to deploy properly, allowing excessive forward occupant movement and increasing injury risk.

4
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Qin Pro DM pretensioner internal resistance aging caused high resistance.

✓
At 80,000 km, the airbag warning light stayed on constantly. VDS read DTC B1799-00. The technician measured front passenger second-stage pretensioner resistance at 3.5Ω, outside the standard 2.0-3.0Ω range. The B-pillar lower harness connector showed no oxidation or looseness, and seat wiring had no damage. Diagnosed the fault as pretensioner internal resistance wire aging causing resistance drift. Replaced the OEM front passenger seatbelt assembly. Post-repair resistance measured 2.2Ω. Cleared the fault codes; system self-check passed and the warning light went out.
Original source ↗
BYD DTC AI Analysis

Song MAX seat track pinches wiring harness, causing intermittent high resistance

✓
Airbag warning light illuminates intermittently, typically on cold starts and clearing after driving some distance. VDS logged B1799-00 as an intermittent fault. The technician performed a harness wiggle test; wiggling the wiring beneath the passenger seat reproduced the fault. Disassembly revealed the seat rail mounting bolt crushing the seatbelt pretensioner harness, partially fracturing the internal copper wires. Contact resistance fluctuated between 2.5-4.5Ω with seat position changes. Repaired the damaged harness, rerouted the wiring clear of the seat rail travel range, and protected it with waterproof tape and corrugated tubing. Fault resolved.
Original source ↗
BYD DTC AI Analysis

Resistance mismatch in aftermarket parts after Qin EV accident repair

✓
After front collision repairs, the airbag warning light stayed on. VDS read B1799-00 (resistance too high) and B1798-00 (resistance too low). The passenger seatbelt assembly was an aftermarket part; the pretensioner measured 3.8Ω and the connector was loose. Replaced it with a genuine OEM unit, seated the connector fully and locked it, and measured 2.1Ω. Cleared the codes and the SRS self-test passed. Use genuine OEM SRS parts for accident repairs.
BYD DTC AI Analysis

Loose connector lock tab on Tang DM caused contact resistance fluctuation

✓
Airbag warning light intermittently illuminated on rough roads; normal on flat surfaces. VDS read B1799-00 as a history fault. Inspection found the passenger-side second-stage pretensioner connector lock loose—vehicle vibration caused slight plug displacement and poor contact. Oscilloscope monitoring caught resistance spiking to 4.2Ω during the fault. Replaced the pretensioner connector using a genuine wiring harness repair kit, secured the connection, and applied conductive grease to the pins to prevent oxidation. Road testing on rough surfaces after repair confirmed the fault cleared.
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.