AU
B1600-00

This DTC indicates the SRS (Supplemental Restraint System) control unit (ACU) detects an open circuit or high resistance in the driver front airbag ignition circuit — Seal U

Safety System

This DTC indicates the SRS (Supplemental Restraint System) control unit (ACU) detects an open circuit or high resistance in the driver front airbag ignition circuit.

The ACU continuously monitors the airbag module circuit resistance through its internal diagnostic circuit.

Normal resistance is 2.0-2.4 Ω.

Resistance exceeding the threshold (usually >6 Ω) or a completely open circuit triggers DTC B1600-00.

The system then enters fail-safe mode and disables the driver-side airbag, preventing deployment during a collision.

The instrument panel airbag warning lamp remains illuminated to alert the driver.

Possible causes include the airbag module, clock spring (spiral cable), wiring harness connectors, or the ACU internal sampling circuit.

3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Fatigue fracture or poor contact in the clock spring (airbag spiral cable) internal flat cable. Frequent steering wheel rotation breaks the internal conductive coil, causing an intermittent or permanent open circuit.
  • 2Driver airbag module connector (yellow plug) loose, oxidized, pins backed out, or locking mechanism failed, causing excessive contact resistance or a complete open circuit.
  • 3Open circuit or abnormal resistance in the airbag module inflator igniter, typically due to internal defects or prolonged storage.
  • 4A damaged steering column wiring harness sleeve below the steering wheel causes internal wires to bend repeatedly during steering wheel rotation, resulting in broken copper strands or a short circuit due to worn insulation.
  • 5SRS control unit (ACU) internal sampling circuit fault, software false report, or unstable 12V power supply/ground causing an open-circuit misdiagnosis.
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds to fully discharge the SRS backup power supply; wear an anti-static wrist strap to prevent accidental airbag deployment.
  • 2
    Visual inspection: Verify the yellow dedicated SRS connectors under the steering wheel and dashboard are fully seated and the locking tabs are engaged. Inspect the pins for oxidation, corrosion, or deformation.
  • 3
    Simulation test: Remove the driver-side airbag module. Connect a 2.2Ω/0.5W standard resistor in parallel at the wiring harness connector to simulate a normal airbag load. Reconnect the battery and turn the ignition ON. If the fault code changes to a history code or disappears, the airbag module is faulty.
  • 4
    Clock spring inspection: Disconnect both clock spring connectors. Use a multimeter to measure the resistance between the terminals. Normal resistance is <1Ω. Slowly turn the steering wheel and check for an intermittent open circuit (resistance spikes to infinity).
  • 5
    Wiring harness continuity test: Measure wiring harness continuity from the ACU connector to the airbag connector. Focus on the continuity and insulation of the wiring harness near the steering column. Check body ground points G101 and G102 for looseness.
  • 6
    Component replacement: Based on test results, replace the clock spring (center during installation), repair the wiring harness, or replace the airbag module (record the new module's resistance value and verify it is within tolerance).
  • 7
    System configuration: Use the BYD dedicated diagnostic tool VDS or ED400 to perform the 'SRS System Configuration' or 'Coding' function (if replacing a module), clear the fault code, and perform 'System Self-check'.
  • 8
    Function check: Reassemble all components and reconnect the battery. Turn the ignition switch to the ON position and verify the airbag warning light turns off after the 6-second self-check. Perform left and right full-lock steering tests to confirm the intermittent fault does not recur.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD S6 B1600 Fault Code Diagnosis and Clock Spring Replacement

✓
Symptoms: Airbag warning light constantly on. Scan tool read DTC B1600. Diagnosis: The technician removed the driver's airbag and bridged the airbag connector with a 2.2-ohm resistor to simulate the component. The fault code remained, ruling out a fault in the airbag module itself. The technician then tested resistance across the clock spring and found an open circuit, diagnosing a fractured internal ribbon cable. Resolution: Replaced the clock spring with a genuine unit, reassembled and centered it, and cleared the fault codes with the scan tool. The airbag warning light returned to normal.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Song DM: Backed-out pin in Vehicle Control Unit wiring harness causes system communication fault (Related case)

✓
Symptoms: Vehicle unable to read the Vehicle Control Module (VCM); communication interruption fault codes present. Diagnosis: Inspected power supply, ground and CAN bus connections. Found a backed-out terminal at the GJK14 harness junction on pins G09-14/15, causing the communication signal to drop out. For B1600 faults, inspect the airbag harness connectors for backed-out or loose terminals. Resolution: Repaired the backed-out terminal, fully seated the harness connectors, and re-secured the harness bracket to prevent it from loosening again.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

GM B1600 fault code diagnosis and power system troubleshooting

✓
Symptoms: Instrument cluster displays DTC B1600 and the airbag warning light illuminates; some cases occur following battery discharge. Diagnosis: Check if battery voltage is below 11V (discharge may trigger ACU false faults), inspect all yellow airbag connectors for looseness, and check if earth cable connections are tight. Resolution: If caused by battery discharge, charge or replace the battery and clear the DTC. If connectors are loose, reconnect and wrap with electrical tape to secure. If the airbag light illuminates while driving, perform an emergency power cycle by disconnecting the negative terminal for 5-10 minutes, but take the vehicle to a service centre for thorough inspection and repair as soon as possible.
Original source ↗
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]