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B1797-00

This DTC indicates the front passenger seat belt pretensioner (second-stage deployment circuit) resistance is 0 Ω, indicating a short circuit — Qin Plus

Safety System

This DTC indicates the front passenger seat belt pretensioner (second-stage deployment circuit) resistance is 0 Ω, indicating a short circuit.

In the BYD SRS (Supplemental Restraint System) architecture, the dual-stage pretensioner deploys in stages based on collision severity: the first stage provides light tightening, and the second stage provides strong tightening to secure the occupant.

A 0 Ω resistance usually indicates an internal short circuit in the pretensioner generator winding, a wiring harness short to ground, or a short between connector terminals.

Upon detecting this fault, the SRS ECU enters fail-safe mode and disables the pretensioner circuit.

This may cause the second-stage protection to fail during a collision or create a risk of unintended deployment; therefore, the system illuminates the airbag warning lamp.

5
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Worn seat rails shorted the wiring harness

✓
Vehicle: Qin EV300 2018. Customer reported the airbag warning light on. Scan tool retrieved DTC B1797-00. Inspection found the passenger seat base harness chafed against the metal bracket when the seat was in the full forward position, wearing through the insulation and causing a short to ground. Repaired the damaged harness (3 wires, including 1 pretensioner signal wire), re-secured the harness routing, added corrugated tubing protection, and repositioned the cable clips to avoid contact with moving parts. Fault resolved.
BYD DTC AI Analysis

Connector corrosion and short circuit after water ingress

✓
Vehicle: Qin 100 2017. After driving through water, the passenger carpet was wet and the airbag light came on. Disassembly revealed water in the pretensioner connector under the passenger seat. Copper terminals had oxidized, producing green corrosion that shorted adjacent terminals. Repair: Cleaned the connector terminals with electronic cleaner and a specialty brush, dried the wiring harness, applied conductive grease, and replaced the connector seal. Pretensioner resistance measured normal at 2.3Ω. Cleared fault codes; no recurrence.
BYD DTC AI Analysis

Pretensioner generator internal short circuit

✓
Vehicle: Qin EV450 2018. Replaced the passenger side seat belt assembly after collision repairs. Post-installation DTC B1797-00 set. Measured the new seat belt pretensioner resistance at 0.2Ω (near short). Disassembling the old part revealed the new unit was aftermarket with an internal bridge wire design defect. Solution: Installed a genuine passenger side seat belt assembly (including pretensioner). Resistance: 2.8Ω. Fault code cleared after installation; SRS self-diagnostic passed.
BYD DTC AI Analysis

Aftermarket seat heater installation caused short circuit

✓
Model: Qin 80 2017. One week after the customer installed an aftermarket passenger seat heating pad, the airbag warning light came on. Inspection found incorrect splicing during the power tap; damaged insulation on the heating pad power wire had shorted to the pretensioner harness. Fix: Removed the unauthorized modification, restored the factory harness insulation with heat-shrink tubing, and remeasured pretensioner circuit resistance and insulation to ground. Advised the customer that SRS system wiring prohibits unauthorized modification.
BYD DTC AI Analysis

SRS ECU detection circuit false positive

✓
Model: Qin EV300 2017. Measured pretensioner and harness resistance multiple times; readings were normal (2.5Ω, good insulation to ground), but the DTC kept returning. Diagnosis: SRS ECU internal sampling circuit fault causing false 0Ω detection. Fix: Replaced the SRS control unit (programmed to match vehicle VIN and configuration codes). After replacement, the DTC has not returned and system function is normal.
Other Qin Plus 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.B110913DTC B110913 indicates an open signal circuit for the PM2.5 rapid detector (in-cabin air quality sensor). This sensor typically mounts inside the air conditioning system intake duct. It monitors in-cabin PM2.5 concentration in real time and provides data to the automatic air conditioning system for intelligent control of the air purification function. The BYD diagnostic protocol uses sub-code '13' to specifically indicate an open signal circuit. Although this fault theoretically affects a comfort feature, BYD Qin series vehicles classify it as a Level 3 (severe) fault. This classification occurs because the air conditioning system interacts with the battery thermal management system (e.g., monitoring battery cooling intake air quality). The fault can disable the automatic air conditioning mode and prevent the air purification function from operating. In extreme cases, it affects the battery compartment intake air quality assessment, triggering the 'repair immediately' strategy.B110AThis DTC indicates interrupted CAN bus communication or abnormal data between the air conditioning control unit (ACU) and the PM2.5 air quality sensor. The PM2.5 sensor monitors particulate concentration inside and outside the vehicle and provides the basis for purification control in the automatic air conditioning system. The ACU triggers this fault if it fails to receive a valid CAN message from the sensor within the specified period (usually 100-500 ms), if message verification fails, or if the signal frame times out. Although this fault does not affect vehicle driving safety, it disables the automatic air purification function. The air conditioning system cannot automatically switch between recirculation and fresh air modes or activate the air purification mode based on air quality. A persistent fault may restrict the thermal management strategy.
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.