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B1650-00

DTC B1650-00 indicates the passenger seat belt pretensioner circuit resistance falls below the normal threshold set by the SRS control module (typically <2 — Atto 3

Safety System

DTC B1650-00 indicates the passenger seat belt pretensioner circuit resistance falls below the normal threshold set by the SRS control module (typically <2.0Ω; normal range is 2.0-3.0Ω).

The pretensioner contains a pyrotechnic squib.

The ECU continuously monitors the squib resistance using a low-current signal.

Low resistance typically indicates a short to ground in the squib circuit, a ground fault from damaged wiring insulation, an internal connector short, or an internal short within the pretensioner component.

This fault forces the SRS system into a degraded mode, meaning the pretensioner may fail to deploy during a collision (seat belt fails to tighten) or may deploy inadvertently (unexpected firing).

ISO 15031 and BYD safety system design classify this as a Level 2 safety fault requiring immediate repair.

5
Cases Logged
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin Pro front passenger seat wiring harness chafed, short to ground

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Symptom: Airbag warning light on instrument cluster stays on. Read DTC B1650-00 (passenger pretensioner resistance too low). Diagnosis: Checked wiring harness under passenger seat. Found that the seat rail fixing clip had chafed through the insulation of the yellow SRS harness over time, causing the copper conductor to short to the seat frame. Measured resistance: 0.8Ω. Repair: Cut out the damaged section and repaired it by soldering in high-temperature wire. Insulated the repair with double-layer heat shrink tubing. Rerouted the harness and added a protective sleeve. Cleared fault codes. Fault resolved.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Song MAX front passenger pretensioner internal short circuit

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Symptoms: After sitting overnight, the airbag warning light stayed on at startup. No collision history. DTC B1650-00. Diagnosis: Disconnected the passenger side seatbelt pretensioner connector. Measured pretensioner internal resistance: 1.2 Ω (low). Measured harness ground resistance: >1 MΩ (normal). Determined the internal igniter had shorted from moisture ingress. Repair: Replaced the passenger side seatbelt assembly (includes pretensioner). Torqued the pretensioner mounting bolts to 9–11 N·m. Cleared fault codes. System returned to normal.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Yuan EV passenger-side B-pillar connector water ingress short circuit

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Symptoms: After rainfall, started the vehicle and the airbag warning light illuminated. The scan tool displayed B1650-00. Diagnosis: Checked the SRS connector located beneath the B-pillar and found the connector seal had deteriorated. Rainwater ingress caused a short circuit between the pins, measuring 1.5Ω. After cleaning the water stains, the resistance returned to normal, but the connector had oxidised. Repair: Replaced the SRS connector (yellow waterproof plug), crimped the terminals using a special crimping tool, rewrapped the joint with waterproof tape, and cleared the fault.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Tang DM: Pretensioner resistance abnormal after collision

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Symptoms: After a low-speed impact (front bumper damaged), the airbags did not deploy but the warning light came on. DTCs B1650-00 and B1651-00 stored. Diagnosis: The impact sensor triggered but didn’t reach the airbag deployment threshold. The impact caused the passenger-side pretensioner’s internal resistance wire to shift and short-circuit. Resistance measured 1.8 Ω. Repair: Replaced the passenger seatbelt assembly (the pretensioner is single-use; replace if triggered or damaged). Used a scan tool to perform SRS system configuration and calibration, then cleared the fault codes.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin EV450 ECU falsely reporting low resistance

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Symptoms: Intermittent B1650-00, occurring when cold and disappearing when warm. Wiring harness and pretensioner measurements were normal. Diagnosis: Used an oscilloscope to check the SRS ECU sampling signal. Found internal reference voltage drift in the ECU, causing it to misjudge the pretensioner resistance as too low under cold conditions. Solution: Replaced the airbag control module (SRS ECU) and performed online matching programming (writing the vehicle VIN and configuration codes). This completely resolved the fault.
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.