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 8

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 8
  • 1Frequent seat movement and chafing damage the insulation of the SRS wiring harness under or beside the front passenger seat, causing it to contact metal body parts and create a short to ground.
  • 2Bent or backed-out pins in the airbag connector (KJ10), or water ingress or oxidation inside the connector causing a short circuit between terminals or to ground.
  • 3The internal igniter component in the right front seat side airbag module shorts out after aging, moisture exposure, or impact, causing the resistance to drop abnormally.
  • 4Vehicle wading or improper interior cleaning causes water ingress in the wiring harness connector under the seat, resulting in insulation failure between pins or to ground.
  • 5Internal fault in the SRS control unit monitoring circuit or software error causing a false short to ground detection.
What To Do
  • 1
    Safety preparation: Turn the power switch to OFF, disconnect the negative battery cable, and wait at least 90 seconds for the SRS capacitor to fully discharge to prevent accidental airbag deployment.
  • 2
    Visual inspection: Remove the front passenger seat (if necessary). Inspect the SRS wiring harness under the seat frame, around the seat tracks, and below the B-pillar for wear, crushing, 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 disconnect it carefully (do not touch terminals directly with metal tools). Use a thin plastic strip to pry open the short-circuit protection tab.
  • 4
    Wiring insulation test: Use the multimeter resistance setting to 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 normal value is greater than 1MΩ. If the resistance is too low, the wiring harness is shorted to ground. Repair or replace the wiring harness.
  • 5
    Circuit continuity test: Measure the resistance between wiring harness connector KJ10 and the corresponding SRS ECU pins (K71-18 and K71-17). The resistance must be less than 1 Ω. High resistance indicates an open circuit or high line 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 specific vehicle standards). If the resistance is close to 0Ω or <1Ω, this indicates an internal short circuit. Replace the airbag module.
  • 7
    Repair and Replacement: Based on test results, repair damaged wiring harnesses (re-wrap and adjust routing), clean or replace connectors, or replace the airbag module or SRS ECU. Never simply clear the fault code without performing repairs.
  • 8
    System verification: Restore all connections, verify the connectors lock securely, connect the battery, set the power to ON, wait 20 seconds, and verify the SRS warning lamp turns off after the self-check. Clear the fault code using the diagnostic tool, 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 8 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: 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]