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B1650

DTC B1650 indicates the SRS (Supplemental Restraint System) control module detects the front passenger-side seat belt pretensioner igniter circuit resistance is below the calibrated threshold (typically <1 — Atto 3

Safety System

DTC B1650 indicates the SRS (Supplemental Restraint System) control module detects the front passenger-side seat belt pretensioner igniter circuit resistance is below the calibrated threshold (typically <1.0 Ω; normal range: 2.0-3.0 Ω).

This indicates a potential short circuit in the internal pretensioner bridge wire, or a short to ground or wire-to-wire short in the harness.

This fault prevents the SRS from triggering the front passenger seat belt pretensioner during a collision (loss of pretensioning protection), or creates a risk of unintended deployment in extreme cases.

The system illuminates the airbag warning lamp and may disable the front passenger airbag deployment function.

In some BYD model years, this code may also indicate an Occupant Classification System (OCS) communication fault.

However, based on the provided fault context, prioritize checking the pretensioner assembly and its wiring harness resistance.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Seat belt pretensioner internal squib short circuit (internal bridge wire broken and shorted to ground, or manufacturing defect causing excessively low resistance)
  • 2Chafed wiring harness insulation under the seat or inside the B-pillar trim panel causes the power wire to short to body ground.
  • 3Pretensioner connector (yellow waterproof plug, usually located under the seat or at the base of the B-pillar): Water ingress, oxidation, or bent pins causing a short circuit between pins.
  • 4Vehicle wading, damp socket after deep interior cleaning, or electrical leakage due to prolonged exposure to a damp environment.
  • 5SRS control module internal sampling circuit fault or loss of calibration data causing incorrect resistance measurement.
What To Do
  • 1
    Safe power-down: Turn off the ignition switch, disconnect the negative battery terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment.
  • 2
    Locate the component: Remove the front passenger lower B-pillar trim and seat side trim, then find the yellow seat belt pretensioner connector (usually integrated into the bottom of the seat belt retractor or below the B-pillar).
  • 3
    Visual inspection: Check the connector for looseness, water ingress, white oxidation marks, or bent pins; check the wiring harness mounting near the seat rail for wear or crush marks.
  • 4
    Resistance measurement: Use a dedicated low-current multimeter (or dedicated airbag system tester) to measure resistance at the pretensioner connector. Normal resistance is 2.0-3.0 Ω; a reading <1.0 Ω indicates a short circuit. Never measure directly using a standard multimeter resistance setting, as excessive current may deploy the pretensioner.
  • 5
    Harness isolation test: Disconnect the pretensioner connector. Measure the resistance from the harness side to ground (should be infinite) and the resistance between the harness wires (should be infinite) to determine whether the short circuit is in the harness or the pretensioner itself.
  • 6
    Replacement verification: If inspection confirms a short circuit in the pretensioner body (internal fault), replace the front passenger seat belt pretensioner assembly. If the wiring harness is faulty, repair the damaged section (solder and insulate with double-layer heat-shrink tubing).
  • 7
    System Reset and Verification: Restore all connections and turn on the power. Use the BYD VDS or a dedicated diagnostic tool to clear the fault code. Perform the SRS system self-check cycle (cycle the ignition switch ON-OFF three times). Verify the warning light turns off and B1650 does not return. Finally, perform a road test to verify the repair.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Song Plus DM-i B1650 Fault After Wading Through Water

✓
After driving through water, the SRS warning light remained illuminated on the instrument panel. The diagnostic tool retrieved DTC B1650. Removed the passenger seat and lower B-pillar trim panel. Found water inside the pretensioner connector (yellow plug) beneath the seat. The pins had short-circuited due to electrolyte formation between them; resistance measured only 0.4 Ω. Cleaned the plug contacts with anhydrous ethanol, thoroughly dried with compressed air, applied special conductive grease, and reassembled. The resistance reading returned to 2.1 Ω. Cleared the DTC, resolving the fault. Recommend checking the vehicle floor sealing.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin Pro EV: Abnormal seatbelt pretensioner resistance after accident repair

✓
After replacing the front passenger seatbelt assembly on the collision-damaged vehicle, DTC B1650 set. Measured the old pretensioner resistance with a dedicated airbag tester: 0.6Ω (internal short); the new component measured 2.3Ω (normal). Further inspection found the impact had deformed the internal pins of the wiring harness connector, causing a short between the signal wire and earth. Replaced the wiring harness connector terminals and repaired the pretensioner to resolve the fault. Tip: On collision-damaged vehicles, pretensioners may have internal bridge wire fractures from impact, causing short circuits even when externally intact. Always verify by measuring resistance.
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Yuan EV: Seat modification caused wiring harness damage and short circuit

✓
After the owner self-installed full-coverage seat covers and seat heating pads, the SRS light came on. Inspection found that the fixing clips had pierced the pre-tensioner wiring harness beneath the passenger seat during installation, shorting the live wire to chassis ground. Measured resistance dropped to 0.3Ω. Removed the aftermarket accessories and stripped back the harness, revealing exposed copper conductors. Repair: cut out the damaged section, re-soldered the harness, insulated with double-layer heat-shrink tubing, rerouted the harness, and added corrugated tubing for protection, ensuring no interference with seat moving parts.
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Tang DM Intermittent B1650 Fault (Wiring Harness Wear)

✓
The DTC appeared intermittently. The SRS warning light came on after driving over rough roads. Diagnosis found the wiring harness retaining clip below the B-pillar had detached. As the seat moved back and forth, the metal bracket edge repeatedly pinched and chafed the harness, wearing through the insulation and causing the internal copper wires to short intermittently to ground. Re-secured the harness, wrapped it with fleece tape and corrugated tubing, and adjusted the slack to prevent contact with sharp edges. This completely resolved the fault. For intermittent faults like this, check for dynamic harness chafing.
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: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself. Sources: [1]