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AU
B1799

DTC B1799 indicates the squib circuit resistance of the front passenger-side second-stage seat belt pretensioner (usually located under the front passenger seat or lower B-pillar) exceeds the SRS ECU threshold (standard value: 2 — Atto 3

Safety System

DTC B1799 indicates the squib circuit resistance of the front passenger-side second-stage seat belt pretensioner (usually located under the front passenger seat or lower B-pillar) exceeds the SRS ECU threshold (standard value: 2.0 Ω ± 0.4 Ω; typically triggers at >2.4 Ω).

This passive safety fault in the Supplemental Restraint System (SRS) means the ECU detects a high-resistance condition in the pretensioner circuit.

Poor contact, a partial open circuit in the wiring, or an aging internal pretensioner squib can cause this condition.

This fault may prevent the second-stage pretensioner from deploying correctly during a collision, reducing occupant restraint protection.

The SRS warning light remains illuminated to alert the driver.

5
Cases Logged
Real-World Cases
BYD DTC AI Analysis

BYD Qin Pro B1799 DTC – Oxidized Connector Causing High Resistance

✓
A 2019 BYD Qin Pro arrived with the airbag warning light constantly on. VDS retrieved DTC B1799-00. The technician removed and inspected the pretensioner connector beneath the front passenger seat and found visible green oxide inside—the vehicle had previous water exposure. The pretensioner measured 2.1 Ω (normal), but the harness side showed 1.2 Ω contact resistance. The technician cleaned the connector terminals with WD-40 electronic cleaner, applied conductive grease, and re-locked the connector. After clearing the DTC, the system self-test passed and the fault cleared.
Original source ↗
BYD DTC AI Analysis

BYD Song MAX B1799 Fault - B-Pillar Wiring Harness Crush Damage

✓
A 2020 Song MAX had an intermittently illuminated airbag warning light. The diagnostic scan showed code B1799-00 (historical). Inspection found signs the passenger side B-pillar lower trim had been removed (the owner had taken it off earlier for window tinting). Disassembling the B-pillar revealed the pre-tensioner harness trapped between the trim clip and sheet metal, damaging the insulation and partially fracturing the internal copper wires—about three strands remained connected. Resistance across this section measured 3.8Ω (normal is <0.5Ω). Repaired the wiring by cutting out the damaged section, soldering in an extension, and insulating with double-layer heat shrink tubing. Rerouted the harness to prevent pinching. Fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD Tang DM B1799 – High Circuit Resistance from Poor Ground

✓
A 2021 Tang DM showed an airbag warning after accident repairs; VDS reported B1799-00. The vehicle had prior sheet metal work on the passenger-side A-pillar. The pretensioner connector checked normal and the unit measured 2.0Ω, but the negative circuit-to-body resistance was 2.5Ω (should be <0.1Ω). Traced to ground G302 under the passenger seat—the body shop never cleaned it during repairs, so paint residue caused poor contact. Fix: Sanded the ground point to bare metal and retorqued the bolt to 9N·m. Resistance dropped to 0.05Ω. Cleared the DTC; fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD Yuan EV B1799 — Seatbelt pre-tensioner resistance drift due to aging

✓
A 2019 Yuan EV with 60,000 km had the airbag warning light on constantly, storing DTC B1799-00. Resistance at the pretensioner connector measured 3.2Ω (significantly high). Disconnecting the plug and measuring directly across the pretensioner body showed 3.1Ω (specification 2.0±0.4Ω), confirming internal igniter aging caused resistance drift. Wiring harness and connectors were normal. Replaced the front passenger second-stage seatbelt pretensioner assembly (Part No.: 5A-5826000-XX). The new part measured 1.9Ω. After installation, cleared the fault codes and the SRS self-test passed.
Original source ↗
BYD DTC AI Analysis

BYD Song Pro B1799 Intermittent Fault – Resistance Fluctuation Due to Loose Connection

✓
A 2020 Song Pro had an intermittent airbag warning light. VDS read historical fault code B1799-00 (current resistance 2.6Ω, borderline high). The pretensioner connector under the front passenger seat had a broken locking tab; the plug was not fully seated, causing an intermittent connection. Resistance fluctuated between 1.8Ω and 4.5Ω when moving the harness. Replaced the pretensioner connector (with wiring harness pigtail) and ensured full lock. Cleared the fault codes and road-tested continuously for 3 days; the fault did not recur.
Original source ↗
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.