AU
B1632

DTC B1632 indicates the SRS (Supplemental Restraint System) ECU detected a short to power (B+) in the front passenger side airbag igniter circuit (typically the right seat airbag or side curtain airbag) — Atto 8

Safety System

DTC B1632 indicates the SRS (Supplemental Restraint System) ECU detected a short to power (B+) in the front passenger side airbag igniter circuit (typically the right seat airbag or side curtain airbag).

Normally, the airbag igniter circuit maintains a low voltage (near 0V).

The ECU supplies high current only when triggering airbag deployment.

If the ECU continuously detects circuit voltage near battery voltage (12V), it identifies a short to power.

This fault forces the SRS into fail-safe mode, disables front passenger side airbag deployment, and illuminates the airbag warning light.

Potential causes include damaged wiring insulation, shorted connector terminals, an internal short in the airbag module, or a faulty internal ECU driver circuit.

5
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Wiring harness wear under the seat or inside the B-pillar: Frequent front passenger seat adjustment or door operation rubs the wiring harness against metal body edges, damaging the insulation and causing a short circuit to the power wire.
  • 2Connector water ingress or deformed terminals: Water enters the front passenger-side airbag connector (usually located under the seat or inside the B-pillar trim) during vehicle wading, car washing, or due to a blocked sunroof drain hose, causing a short circuit between terminals.
  • 3Airbag assembly internal fault: The internal igniter insulation layer of the front passenger side airbag (curtain or seat airbag) breaks down due to aging, causing the igniter pins to short to ground or power.
  • 4SRS ECU internal drive circuit fault: A damaged ECU internal monitoring circuit or ignition drive transistor triggers a false short circuit fault, or an actual short circuit exists in the internal circuit.
  • 5Unauthorized modification or added equipment: Mistakenly using the airbag wiring harness as a ground or constant power wire when installing aftermarket seat heating, ventilation, or electronic anti-theft equipment abnormally energizes the circuit.
What To Do
  • 1
    Safety Preparation: Set the vehicle to OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to allow the SRS capacitor to fully discharge and prevent accidental airbag deployment.
  • 2
    Fault Confirmation and Freeze Frame Analysis: Connect the diagnostic tool to read DTC B1632. Record the freeze frame data (vehicle speed, temperature, voltage, etc. at the time of occurrence) and confirm whether the fault is current or historical.
  • 3
    Visual inspection: Remove the front passenger seat (seat airbag) or lower B-pillar trim panel (curtain airbag). Check the airbag connector for looseness, water ingress, corrosion, or obvious burn marks. Check the wiring harness for abrasion, crushing, or damaged insulation.
  • 4
    Circuit resistance and voltage measurement: Disconnect the airbag module connector. Use a multimeter to measure the harness-side terminal voltage to ground (should be <1V) and to the power supply (should be <1V). Measure the resistance between the terminals (should be >1MΩ). A measured voltage near 12V indicates a circuit short to power.
  • 5
    Harness continuity and insulation test: Use a multimeter in buzzer mode to measure wiring continuity between the airbag connector and the SRS ECU. Use a megohmmeter to measure insulation resistance between the wiring and the vehicle body (should be >10MΩ). Focus inspection on the harness near the seat slide rails and door hinges.
  • 6
    Airbag module test: Measure the airbag module igniter resistance (normal value is 2.0-3.0 Ω, with slight variation between models). If the resistance is 0 Ω or infinite, or indicates a short circuit to the housing, replace the airbag module.
  • 7
    SRS ECU inspection: If the wiring and airbag assembly are normal and the fault code persists, inspect the ECU connector and pins. If necessary, replace with a known good ECU for testing.
  • 8
    Repair and verification: Repair or replace the damaged wiring harness/connectors/airbag assembly/ECU. Reconnect all components, connect the battery, and clear the fault code. Perform the SRS system self-check (turn the ignition switch ON; the warning light should illuminate for 6 seconds and then turn off). Perform a road test to verify the repair.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Worn front passenger seat wiring harness caused B1632 on Song Pro DM

✓
Vehicle: 2020 Song Pro DM. Mileage: 32,000 km. Symptom: Airbag warning light constantly illuminated on the instrument panel. DTC B1632 stored (front passenger side airbag short to power). Diagnosis: Removed the front passenger seat. The seat rail edge had chafed through the wiring harness at the yellow airbag connector under the seat, exposing copper wires that touched the seat frame (earth). A measurement showed a short to power. Further inspection found the damaged section also contacting the seat heater power line, causing the short. Repair: Repaired the damaged harness, wrapped it in abrasion-resistant corrugated tubing, and rerouted the wiring away from the rail to prevent interference. Cleared the DTCs and the system returned to normal.
BYD DTC AI AnalysisFrom Chinese market (translated)

Water entered the passenger side curtain airbag connector on the Tang EV after wading.

✓
Model: 2021 Tang EV, Mileage: 18,000 km. Symptoms: Airbag warning light came on after driving through water during heavy rain. DTC: B1632. Diagnosis: Inspected the passenger side B-pillar curtain airbag connector. Found significant water staining and verdigris inside, with a micro-short circuit between terminals caused by electrolytic corrosion. Measured 11.8V between the terminal and power supply. Repair: Thoroughly cleaned the connector with electronic contact cleaner, blew it dry, applied conductive grease, and replaced the waterproof seal ring. Cleared the blocked sunroof drain line (root cause). Resolved the fault.
BYD DTC AI AnalysisFrom Chinese market (translated)

Yuan EV airbag module internal short circuit false alarm

✓
Vehicle: 2019 BYD Yuan EV535, Mileage: 56,000 km. Symptoms: Airbag warning light comes on intermittently, DTC B1632 intermittent. Diagnosis: Measured passenger seat airbag resistance normal (2.3Ω), wiring harness insulation good, but bump test reproduced the fault. Disassembly of the airbag assembly revealed a dry solder joint on the internal igniter. During vibration, it occasionally contacted the housing, causing a short to ground or power. Repair: Replaced passenger side airbag assembly (seat airbag). Fault completely resolved.
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Qin Pro (petrol): Aftermarket seat ventilation installation caused a short in the wiring.

✓
Vehicle: 2020 Qin Pro petrol (modified), 21,000 km. Symptoms: Airbag warning light came on one week after seat ventilation system installation, DTC B1632 stored. Diagnosis: Inspection found the installer had mistaken the passenger airbag harness (yellow) for a constant power source, spliced it into the seat ventilation fan supply, energising the airbag circuit. Repair: Removed the illegal wiring modifications, restored airbag circuit integrity using an OEM harness repair kit, replaced the damaged airbag connector, and instructed the owner never to modify airbag circuits.
BYD DTC AI AnalysisFrom Chinese market (translated)

False alarm case due to internal SRS ECU fault

✓
Model: 2019 Song MAX, Mileage: 45,000 km. Symptoms: Repeated DTC B1632 occurrences. Replaced passenger airbag and wiring harness without resolution. Diagnosis: Detailed measurement of the entire circuit from ECU to airbag showed normal resistance, voltage, and insulation, with no short to power. Oscilloscope monitoring revealed intermittent false triggering in the ECU's internal monitoring circuit. Repair: Replaced SRS ECU (requires synchronised immobiliser matching and configuration write). Performed coding and initialisation using dedicated diagnostic equipment. Fault permanently resolved.
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]