AU
B1601-00

DTC B1601-00 indicates the airbag control unit (SRS ECU) detects an abnormally low-resistance path to body ground in the driver frontal airbag (DAB) ignition circuit — Qin Plus

Safety System

DTC B1601-00 indicates the airbag control unit (SRS ECU) detects an abnormally low-resistance path to body ground in the driver frontal airbag (DAB) ignition circuit.

Under normal conditions, the airbag igniter circuit resistance measures 2.0-3.0 Ω, and the insulation resistance to ground exceeds 10 MΩ.

Damaged wiring harness insulation, an internal clock spring short circuit, or a grounded connector terminal significantly reduces circuit resistance (typically below 1 Ω), causing the ECU to register a short-to-ground fault.

This fault prevents the driver airbag from deploying during a collision (fail-safe mode) or, in extreme cases, causes unexpected deployment due to false triggering.

As a critical passive safety hard fault, immediately remove the vehicle from service for repair.

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Cases Logged
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Causes
Likely Causes — Qin Plus
  • 1Aged and damaged insulation on the flat ribbon cable inside the clock spring causes the airbag ignition circuit to short against the metal frame when turning the steering wheel. This is a common fault on BYD Qin series models.
  • 2Long-term chafing near the steering column damaged the driver's airbag wiring harness insulation, causing the copper core to directly contact vehicle body metal components and create a ground path.
  • 3The yellow SRS connector (usually located under the steering wheel or on the left side of the dashboard) develops terminal corrosion or water ingress due to wading, interior cleaning, or a damp environment, causing a short circuit between terminals or to ground.
  • 4After a front-end collision, improperly securing the airbag wiring harness during repairs caused the instrument panel frame or other sharp edges to pinch, crush, and damage the harness.
  • 5SRS ECU internal driver circuit fault or damaged monitoring chip, causing a false short-to-ground report (false fault). Rule out wiring harness faults before confirming.
What To Do
  • 1
    Safe power-down: Turn off the ignition, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS backup power supply capacitor and prevent accidental airbag deployment during repair.
  • 2
    Visual inspection: Remove the trim panels on both sides of the steering wheel. Inspect the clock spring for burn marks or cracks. Check the airbag wiring harness securing points at the steering column and instrument panel frame. Inspect the harness for wear, pinching, or damaged insulation.
  • 3
    Resistance measurement: Disconnect the driver airbag connector (yellow plug). Use a digital multimeter to measure the resistance from each of the two terminals on the harness side (body side) to body ground. The normal reading is infinity (OL). A reading of less than 1 Ω confirms a short to ground.
  • 4
    Sectional isolation: Disconnect the wiring harness connector below the clock spring. Measure resistance to ground upstream (ECU side) and downstream (airbag side) of the clock spring to determine if the short circuit is in the clock spring assembly or the body wiring harness.
  • 5
    Component test: Remove the driver airbag module. Directly measure the resistance between the airbag igniter pins (normal: 2-3 Ω) and the insulation resistance between each pin and the airbag metal housing to confirm the airbag module itself has no internal short circuit.
  • 6
    Repair or replace: If the wiring harness is damaged, repair it using heat-shrink tubing and reroute it away from sharp edges; if the clock spring has an internal short circuit, replace the clock spring (maintain the center position during installation to prevent over-rotation); if the airbag module has an internal short circuit, replace the entire driver airbag assembly.
  • 7
    System verification: Reconnect all connectors, reconnect the battery negative terminal, use the diagnostic tool to clear the fault code, perform an SRS system self-check, confirm B1601-00 does not return, and verify the airbag warning light turns off.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Internal short circuit in the Qin EV300 clock spring caused the airbag warning light to illuminate.

✓
A 2017 Qin EV300 with 82,000 km displayed "Please check SRS system" on the dashboard. The technician retrieved DTC B1601-00. After disconnecting the battery and removing the steering wheel, the technician found slight burn marks at the bottom of the clock spring. Using a multimeter, the technician measured the upstream wiring harness resistance to earth as normal (infinite), but the downstream (airbag side) resistance to earth was 0.3 Ω. The technician replaced the clock spring (Part No.: EG-4121100), cleared the fault code, and the fault did not recur. The root cause was prolonged steering lock usage causing fatigue fracture of the clock spring's internal ribbon cable; the core wire contacted the metal housing, creating a short to earth.
BYD DTC AI AnalysisFrom Chinese market (translated)

Water-damaged vehicle: driver airbag connector corroded and short-circuited

✓
A 2018 Qin EV450 previously had water ingress due to a blocked sunroof drain. One month after the repair, DTC B1601-00 appeared. Inspection found green copper corrosion inside the yellow airbag connector under the steering wheel; pin 2 (airbag low side) was shorted to the connector housing. Cleaning the terminals, applying dielectric grease, and repairing the wiring harness waterproof boot cleared the fault. Water ingress faults like this often trigger multiple SRS DTCs at once. Carefully check the sealing of all yellow connectors.
BYD DTC AI AnalysisFrom Chinese market (translated)

Improperly installed dashboard wiring harness caused a short circuit after accident repair

✓
A 2017 Qin 100 had its instrument panel assembly replaced at a non-authorised repair shop following a front-end collision. One week after handover, the airbag warning light came on. Diagnosis revealed active DTC B1601-00. Removing the instrument panel showed the driver's airbag harness had been trapped by a mounting bolt as it passed through the cross-member. The insulation wore through, exposing the copper core and creating a short to ground. The harness was rerouted and secured with dedicated clips, maintaining more than 20 mm clearance from sharp edges. After repairing the damaged wiring, the fault cleared. This case highlights the importance of correct wiring harness routing in accident repairs.
BYD DTC AI AnalysisFrom Chinese market (translated)

SRS ECU internal monitoring circuit false positive (false short circuit)

✓
A 2017 BYD Qin 80 intermittently set DTC B1601-00. When the fault occurred, the airbag harness showed normal resistance to ground. The DTC could be cleared, but it would randomly recur while driving. Disconnecting the airbag module and connecting a 2.7Ω resistor across the harness side to simulate a normal airbag load did not eliminate the fault. The root cause was an internal monitoring chip failure in the SRS control unit, causing false short-to-ground detection. Replacing the SRS ECU beneath the centre console (which required immobiliser matching and airbag configuration coding) permanently fixed the fault. After ruling out the harness and airbag module, consider these types of false faults.
Other Qin Plus 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]