AU
B1602-00

This DTC indicates a short to power (positive) in the driver-side front airbag (steering wheel airbag) ignition circuit — Seal U

Safety System

This DTC indicates a short to power (positive) in the driver-side front airbag (steering wheel airbag) ignition circuit.

Specifically, the airbag control unit (ACU/SRS ECU) detects abnormal continuity between the driver airbag ignition wiring harness (typically the W/L white-blue and G/R green-red wires) and the vehicle power supply.

Resistance falls below the threshold (normal values exceed 1 MΩ; fault conditions may approach 0 Ω or display a voltage exceeding 1 V).

This severe electrical fault in the airbag system poses two extreme risks: first, the short circuit can trigger unintended airbag deployment, injuring the driver; second, a continuous bypass of the airbag circuit prevents proper deployment during an actual collision.

Potential fault locations include the clock spring (spiral cable), airbag module wiring harness, connectors, or inside the airbag ECU.

3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Internal short circuit in the clock spring (spiral cable): Long-term rotation wears the clock spring beneath the steering wheel, damaging the internal wire insulation and shorting the firing wire to the power wire.
  • 2Airbag wiring harness worn and shorted: Friction or compression damages the insulation of the airbag wiring harness inside the steering wheel or steering column, causing contact with the body power wire.
  • 3Connector water ingress or corrosion: Water exposure or moisture in the driver airbag connector (usually located under the steering wheel or on the airbag module) causes a short circuit between terminals.
  • 4Airbag ECU internal fault: Damaged ACU internal drive circuit incorrectly reports a short circuit fault or actually causes a short circuit.
  • 5Airbag module internal short circuit: Driver airbag igniter internal short to power supply (less common but possible)
What To Do
  • 1
    Safety preparation: Set the vehicle power mode to OFF, disconnect the battery negative terminal, and wait at least 90 seconds (to ensure the airbag capacitor discharges completely).
  • 2
    Initial inspection: Check the driver airbag connector for proper connection. Inspect for signs of looseness, water ingress, or corrosion. Clean and reconnect if necessary.
  • 3
    DTC clearing and reproduction: Connect the diagnostic tool, switch the power mode to ON, and clear the DTC. Wait 20 seconds, then read the codes again to confirm whether the DTC reappears.
  • 4
    Voltage/resistance measurement: Disconnect the airbag module. Measure the voltage to ground (should be <1V) and resistance to ground (should be >1MΩ) at harness terminals G46-1 (W/L wire) and G46-2 (G/R wire). Also measure the resistance between harness terminals G46-1 and G36-18, and between G46-2 and G36-17 (should be <1Ω).
  • 5
    Clock spring check: Disconnect the clock spring from the airbag wiring harness. Measure the resistance between the clock spring pins and from each pin to ground to check for short circuits.
  • 6
    Component replacement test: Install a known-good driver airbag module. If the fault clears, replace the airbag module. If the fault persists, inspect or replace the clock spring wiring harness.
  • 7
    ECU inspection: If all the above checks are normal, measure the airbag ECU power supply and ground. Replace the airbag ECU if necessary.
  • 8
    Final verification: After repair, clear the fault code and perform multiple power cycles to verify the fault does not return and the airbag system self-check is normal.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Poor contact in the airbag connector caused B1602-00 on a BYD Qin.

✓
Symptoms: The airbag warning light on the instrument panel stays on constantly. DTC B1602-00 retrieved via diagnostic scan. Diagnosis: The technician first checked the driver airbag connector and found it not fully seated. They disconnected and securely reconnected it. With the ignition ON, they cleared the DTC using the diagnostic tool and waited at least 20 seconds. They then cycled the ignition OFF and back ON, read the DTCs again, and found the code still present. Next, they measured voltage and resistance to ground at harness terminals G46-1 (W/L wire) and G46-2 (G/R wire). The voltage to ground exceeded 1V (abnormal), indicating a short to power in the harness. Further inspection revealed internal wear in the clock spring causing the short circuit. Solution: Replaced the driver airbag harness (including clock spring), reconnected the airbag module, cleared the DTCs, and road tested the vehicle. Fault resolved.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Song DM Airbag Circuit Fault Reference Case

✓
Symptoms: After a collision or repair work, the airbag warning light illuminates and the diagnostic tool displays airbag system fault codes (including short-circuit faults such as B1602). Diagnostic Process: Used a diagnostic tool to read the fault codes and confirmed an airbag circuit fault. Inspected the airbag module wiring connections and found a loose connector. Checked the clock spring (spiral cable) for continuity and measured the airbag module resistance to verify it was within the normal range (typically 2–5 ohms). Solution: Re-seat the airbag module connector, ensure a secure connection, then clear the fault codes. If the fault persists, replace the clock spring (for the steering wheel airbag). Check the airbag ECU power supply and earth, and replace the ACU if necessary.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Worn clock spring caused short to power in BYD Qin EV450

✓
Symptoms: The airbag warning light suddenly illuminated on an 80,000 km Qin EV450. DTC B1602-00 was stored. Diagnosis: The technician disconnected the battery negative terminal and waited 90 seconds per standard procedure, then removed the steering wheel for inspection. After disconnecting the driver airbag module, the technician measured its resistance at approximately 2.8 Ω (normal). Measuring voltage from the clock spring lower harness to ground showed 12 V on the W/L wire—well above the normal 1 V—confirming a short to power. Removing the clock spring revealed that the internal flat cable insulation had worn through from long-term steering movement, contacting the metal frame and causing the short. Repair: Replaced the clock spring (spiral cable), reconnected all connectors, cleared DTCs, and performed a power-cycle test. The fault did not recur and the airbag system self-test completed normally.
Other Seal U 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]