AU
B1600

DTC B1600 indicates the SRS (Supplemental Restraint System) control unit detects an open circuit or connection failure in the driver front airbag (steering wheel airbag) circuit — Seal U

Safety System

DTC B1600 indicates the SRS (Supplemental Restraint System) control unit detects an open circuit or connection failure in the driver front airbag (steering wheel airbag) circuit.

Specifically, electrical circuit resistance between the airbag control unit and the driver airbag assembly exceeds the standard range (normal: approx. 2-3Ω; fault: typically >10Ω or infinite).

This hard-wired connection fault indicates the control unit continuously fails to establish effective communication with the driver airbag during vehicle self-test or driving.

Upon triggering, the SRS enters fail-safe mode, illuminates the airbag warning lamp, and disables driver airbag deployment.

In a collision, this airbag may fail to inflate normally, severely compromising passive safety performance.

Some early BYD petrol models or specific powertrain systems define B1600 as "mixture too rich." However, based on current DTC information and applicable models (Yuan, Tang, Song, Qin series), this analysis focuses on the airbag system circuit fault.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Clock spring internal open circuit: Frequent steering wheel rotation causes fatigue fracture of the internal flat ribbon cable, resulting in an open circuit.
  • 2Wiring harness connector terminals backed out or loose: especially loose, backed-out, or oxidized pins at mating connectors such as GJK14, or poor contact at the airbag connector under the steering wheel.
  • 3Airbag assembly internal open circuit: Internal open circuit in the airbag squib or excessive contact resistance at the airbag connector.
  • 4Power supply system fault: Battery voltage too low (<11V) or poor connection in the SRS control unit power supply circuit, causing the control unit to incorrectly detect abnormal circuit resistance.
  • 5Physical damage to the wiring harness: Broken internal copper wires in the harness near the steering wheel due to long-term twisting and wear, or incorrect harness connection after accident repairs.
What To Do
  • 1
    Initial diagnosis: Use the dedicated diagnostic tool to read the fault code, determine if B1600 is a current or history fault, and observe if the airbag warning light remains illuminated.
  • 2
    Power supply system check: Measure battery voltage (should be >12V). Check the constant power (B+) and ignition switch power (IG) voltages at the SRS control unit to rule out false faults caused by unstable voltage.
  • 3
    Circuit resistance measurement: Disconnect the battery negative terminal, wait 90 seconds for the capacitor to discharge, unplug the SRS control unit connector, and measure the driver airbag circuit resistance (standard value 2-3 Ω). An infinite reading indicates an open circuit.
  • 4
    Section-by-section troubleshooting: Remove the steering wheel. Check the connection status of the lower clock spring connector (steering column side) and upper connector (airbag side). Measure the continuity of the clock spring (resistance must remain stable when turning the steering wheel).
  • 5
    Dummy load test: Connect a dedicated airbag simulator (2Ω resistor) to the wiring harness in place of the actual airbag. If the fault code clears and the system passes the self-check, the airbag unit is faulty. Otherwise, the wiring is faulty.
  • 6
    Detailed wiring harness inspection: Focus on inspecting wiring harness connectors, such as GJK14, for backed-out pins or looseness. Check for loose retaining clips causing wiring harness pinching or chafing.
  • 7
    Repair verification: After repairing or replacing the faulty component, reconnect all connectors, reconnect the battery negative terminal, clear the fault codes, perform the SRS system self-check cycle (cycle the ignition switch ON-OFF three times), and confirm the warning light turns off and no fault codes return.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD S6 driver airbag harness pin backed out

✓
Symptom: Airbag warning light permanently illuminated on the instrument cluster. Scan tool retrieved DTC B1600 and the system failed the self-test. Diagnosis: The technician performed step-by-step troubleshooting. Checked wiring continuity with a 5W test lamp. Removed the steering wheel to test clock spring continuity. Found a backed-out pin at the GJK14 harness connector, causing infinite circuit resistance. Repair: Reseated the backed-out pin and secured it to ensure reliable contact. Fault cleared. This case shows that wiring harness workmanship issues in BYD vehicles can cause intermittent or continuous open circuits.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

B1600 false fault due to low battery

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Symptoms: Airbag warning light illuminated suddenly while driving or starting, logging DTC B1600. No collision history; airbag system appeared normal. Diagnosis: Checked battery voltage and found it measured only 10.8V, indicating severe discharge. Parasitic current testing identified an aftermarket accessory causing current drain. Measured SRS control unit supply voltage and found that voltage fluctuations caused the control unit to misinterpret airbag circuit resistance as abnormal. Solution: Removed the aftermarket device, fully charged the battery (or replaced the battery), and cleared the fault codes using a diagnostic tool. The airbag warning light extinguished and the fault did not recur. This is a typical false fault caused by unstable supply voltage.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Song DM Wiring Harness Poor Contact Fault Reference

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Symptom context: Although the original case involved a vehicle control unit communication fault, on Song series models DTC B1600 can also result from similar wiring harness workmanship issues. On Song DM variants, technicians discovered backed-out pins at the GJK14 harness connector at pins G09-14/15, causing communication failure. Such pin retraction faults are equally common in airbag systems. Diagnostic points: Inspect the GJK14 connector beneath the steering wheel and the clock spring connector for loose or retracted pins. Measure the harness end-to-end resistance using a multimeter, and turn the steering wheel to check for intermittent open circuits.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Clock spring (spiral cable) internal open circuit fault

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Symptoms: Airbag warning light illuminates when the steering wheel is turned to specific angles, or remains on constantly, storing DTC B1600. Diagnosis: Disconnected the airbag connector and directly measured continuity between the upper and lower terminals of the clock spring. Found an open circuit or intermittent resistance. Disassembled the clock spring and discovered the internal flat ribbon cable had fractured due to fatigue from repeated torsional stress. Repair: Replaced the clock spring with an OEM unit. Reinstalled the steering wheel and ensured correct centering. Cleared fault codes and tested the system at various steering angles – all functions normal. This is one of the most common hardware failure causes for B1600 in BYD vehicles.
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Models Rich Mixture Fault Description (Different System Definitions)

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Note: In some BYD petrol models or early systems, DTC B1600 may be defined as "System Too Rich". Symptoms include the engine warning light illuminating, increased fuel consumption, and rough idle. This condition is unrelated to the SRS (airbag) system. It involves abnormal fuel system pressure (>4.0 bar), a blocked air filter, faulty oxygen sensor signals, or intake system leaks. During diagnosis, first confirm which system the DTC belongs to (SRS versus Engine) to avoid misdiagnosis. If you confirm an engine system fault, check fuel trim data, the mass airflow sensor, and oxygen sensor signals.
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]