AU
B1631-00

DTC B1631-00 indicates the airbag control unit (SRS ECU) detected a short to ground in the front passenger (right front) seat side airbag inflator circuit — Atto 3

Safety System

DTC B1631-00 indicates the airbag control unit (SRS ECU) detected a short to ground in the front passenger (right front) seat side airbag inflator circuit.

The SRS ECU verifies circuit integrity by monitoring the airbag inflator circuit resistance.

Normally, this circuit exhibits high resistance (open circuit or a specific resistance range, typically >1MΩ insulation to ground).

If the ECU detects an abnormal resistance drop between the inflator circuit and body ground (below the threshold, typically <1Ω), it registers a short to ground.

This fault triggers the safety protection mechanism.

The ECU disables the airbag to prevent accidental deployment, illuminates the instrument cluster SRS warning light, stores the DTC, and may sound a warning buzzer.

Because the side airbag is critical for side impact protection, this fault disables front passenger side impact protection and constitutes a severe safety fault.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Frequent seat movement and friction damage the insulation on the SRS wiring harness under or beside the front passenger seat, causing it to contact metal body components and short to ground.
  • 2Bent or backed-out pins in airbag connector (KJ10), or water ingress or oxidation inside the connector causing a short circuit between terminals or to ground.
  • 3The right front seat side airbag module igniter component develops an internal short circuit after aging, moisture exposure, or impact, causing an abnormal drop in resistance.
  • 4Vehicle wading or improper interior cleaning causes water ingress into the under-seat wiring harness connector, resulting in insulation failure between pins or to ground.
  • 5SRS control unit internal monitoring circuit fault or software error causing incorrect detection of a short to ground.
What To Do
  • 1
    Safety preparation: Turn the power mode to OFF, disconnect the negative battery cable, and wait at least 90 seconds to ensure the SRS capacitor fully discharges and prevent accidental airbag deployment.
  • 2
    Visual inspection: Remove the front passenger seat (if necessary). Carefully inspect the SRS wiring harness under the seat frame, around the seat rails, and below the B-pillar for wear, pinching, cuts, or water stains. Focus on the condition of connector KJ10.
  • 3
    Disconnect the airbag module: Locate the right front seat side airbag wiring harness connector (KJ10) and carefully disconnect it (do not touch the terminals directly with metal tools). Use a thin plastic strip to lift the short-circuit protection tab.
  • 4
    Circuit insulation test: Set a multimeter to the resistance setting. Measure the resistance between harness-side KJ10-1 (Y/L wire) and body ground, and between KJ10-2 (B/Y wire) and body ground. The resistance must be greater than 1 MΩ. If the resistance is too low, the harness is shorted to ground. Repair or replace the harness.
  • 5
    Circuit continuity test: Measure the resistance between harness connector KJ10 and the corresponding SRS ECU pins (K71-18 and K71-17). Resistance must be less than 1 Ω. High resistance indicates an open circuit or high circuit resistance; check the intermediate connector.
  • 6
    Airbag module test: Measure the resistance between the two terminals of the airbag module. The normal value is approximately 2.0-3.0Ω (refer to vehicle specifications). If the reading is close to 0Ω or <1Ω, the module has an internal short circuit. Replace the airbag module.
  • 7
    Repair and replacement: Based on test results, repair damaged wiring harnesses (re-wrap, adjust routing), clean or replace connectors, or replace the airbag module or SRS ECU. Never clear the fault code without performing the repair.
  • 8
    System verification: Restore all connections, ensure connectors lock into place, and connect the battery. Set the power mode to ON and wait 20 seconds. Confirm the SRS light turns off after self-check. Use the diagnostic tool to clear the fault code, then perform a road test or simulation test to confirm fault resolution.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Seat movement on the Qin EV300 loosened the connector, triggering code B1631-00.

✓
A 2017 Qin EV300 with 42,000 km on the clock suddenly showed the airbag warning light. Connected a VDS2000 scan tool and retrieved DTC B1631-00. Found the KJ10 connector under the front passenger seat was not fully locked, with a gap of about 2 mm. Seat movement caused the connector to vibrate, creating an intermittent short to ground. Reseated the connector and made sure the locking tab fully engaged. Cleared the fault codes and road-tested the vehicle; the fault did not return. Analysis: The seat rails on this model slide frequently, and the connector sits in a high-stress position, making it prone to loosen over time.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Chafed wiring harness caused passenger-side airbag short to ground on Qin 80

✓
2017 BYD Qin 80. After three years of use, the SRS warning light stayed on constantly. A diagnostic scan returned DTC B1631-00. After removing the passenger seat, we found the protective harness sleeve between the seat frame and the vehicle body had worn through from long-term friction, exposing the copper strands of the Y/L wire (KJ10-1). The strands contacted the metal seat frame; resistance to ground measured only 0.8 Ω. Repair: We cut out the damaged wire section, soldered the connections, and insulated them with heat-shrink tubing. We rerouted the harness and added securing points to keep it away from the frame, then re-wrapped the harness with corrugated tubing. After the repair, resistance to ground measured >10 MΩ. Fault cleared.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin EV450 Side Airbag Module Internal Short Circuit

✓
The airbag light on a 2018 Qin EV450 stayed on after repairs for a minor side collision. Read DTC B1631-00. Inspected under-seat harness: no damage, connectors dry. Disconnected airbag module; measured harness-side insulation to ground >5MΩ (normal), continuity good. Measured resistance across module terminals: 0.2Ω (spec 2.0±0.5Ω). Determined collision caused internal igniter short. Replaced right front seat side airbag module (part number: K4A-5824600). After installation, performed ECU configuration and self-test. Cleared codes; SRS light went out.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Water ingress into the SRS connector after wading caused a false B1631-00.

✓
2017 BYD Qin 100. After driving through water, the instrument cluster displayed an airbag fault. Found DTC B1631-00 and multiple SRS-related faults. Removed the passenger seat and found obvious water staining and green copper corrosion inside the KJ10 connector, with reduced insulation resistance between the pins. Repair: Thoroughly cleaned the connector using electronic cleaner, dried it with compressed air, and applied conductive protectant. Measured the wiring harness insulation resistance to ground and found it had returned to the normal range (>1MΩ). Cleared the fault codes and road tested; only B1631-00 appeared intermittently. Finally replaced the KJ10 connector assembly to completely resolve the fault. Tip: For vehicles exposed to water, pay special attention to the sealing of SRS connectors in low-lying areas under the seats.
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]