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B16101B

B16101B is an ISO 15031-6 standard diagnostic trouble code (DTC) — Seal U

Safety System

B16101B is an ISO 15031-6 standard diagnostic trouble code (DTC). 'B' represents the Body system, '16' specifies the airbag system (SRS), '10' refers to the Passenger Frontal Airbag circuit, and '1B' is the sub-fault code indicating circuit resistance exceeds the threshold (open circuit or high resistance).

This fault indicates the SRS ECU (airbag control unit) cannot establish effective communication with the Passenger Frontal Airbag module and cannot detect normal squib resistance (standard value: 2.0-3.0Ω).

The ECU triggers this fault code when it detects infinite circuit resistance (open circuit) or resistance exceeding 6.0Ω.

The airbag system enters fail-safe mode.

The passenger frontal airbag will not deploy in a collision, and the instrument panel SRS warning light illuminates continuously, indicating a functional defect in the occupant restraint system.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Poor contact, backed-out pins, or oxidized terminals at the front passenger airbag module wiring harness connector interrupt signal transmission. This is the most common cause of the fault, especially after the vehicle wades through water or operates in high-humidity environments.
  • 2Internal copper wires in the instrument panel wiring harness break or make poor contact at bend points (such as near the air conditioning duct or instrument panel frame edge) due to long-term vibration, causing an intermittent or permanent open circuit.
  • 3Airbag module internal squib open circuit or abnormally high resistance. Common causes include moisture inside the airbag module, component aging, or damage from previous improper testing (direct measurement using a multimeter on the resistance setting).
  • 4Deformed, loose, or corroded terminals on the SRS ECU connector (such as the KG10 connector) cause poor contact with the wiring harness, preventing the circuit check.
  • 5After accident repairs, incorrect installation of the front passenger airbag module, or failure to fully seat the wiring harness connector and push the CPA lock into the locked position, causes the connector to detach due to vibration while driving.
What To Do
  • 1
    Safety preparation: Set the power mode to OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor and prevent accidental airbag deployment. Wear an anti-static wrist strap. Do not use radio equipment near the airbag.
  • 2
    Initial diagnosis and code clearing: Connect the VDS or dedicated diagnostic tool, enter the SRS system, then read and record the fault code. Clear the fault code, switch the power mode to ON, and wait 20 seconds for the system to complete its self-check. If the fault code reappears immediately, confirm it as a current fault. If it is a history fault, check for intermittent contact issues.
  • 3
    Visual and physical inspection: Remove the front passenger lower dashboard trim panel or glove box (depending on vehicle model). Verify the yellow airbag module connector (usually equipped with a double-locking mechanism) is fully seated. Inspect the connector housing for cracks, backed-out terminals, or signs of corrosion. Verify the wiring harness retaining clips are secure and the harness shows no signs of crushing.
  • 4
    Circuit continuity check: Disconnect the SRS ECU KG10 connector and the front passenger airbag module connector. Push open the shorting bar in the KG10 connector using a thin plastic strip. Measure the harness resistance between the KG10 and airbag connectors using a multimeter. Normal resistance should be less than 1 Ω. If resistance is infinite, check the harness section by section for an open circuit. If resistance fluctuates, check for poor connections.
  • 5
    Airbag module resistance measurement: With the wiring harness completely disconnected, use a dedicated airbag tester or a low-current resistance setting (allowed on some models) to measure the resistance between the two airbag module terminals. The normal value is 2.0-3.0 Ω. A resistance of 0 Ω indicates a short circuit. Infinite resistance or a value greater than 6 Ω indicates an internal airbag module fault; replace the module.
  • 6
    Insulation and short circuit check: Measure the insulation resistance of the airbag wiring harness to ground and to power. Resistance must be greater than 10MΩ. If a short circuit exists, inspect the wiring harness for wear causing contact with the dashboard metal frame or a power wire.
  • 7
    Repair and verification: Repair or replace the faulty wiring harness/connector (e.g., re-crimp terminals, replace backed-out pins, solder broken wires), or replace the faulty airbag module. Fully seat and latch all connectors (listen for a 'click' and verify the locking tab returns to position). Reconnect the battery, power on the vehicle, and perform the SRS system self-check. Confirm DTC B16101B does not return and the airbag warning light turns off after the self-check.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Yuan Plus passenger airbag KG10 connector backed-out pin fault

✓
The SRS warning light stayed on constantly. The diagnostic tool retrieved fault code B1610 (short for B16101B). Measuring between terminal KG10-11 (yellow/black wire) and airbag terminal No. 2 showed infinite resistance. Disassembly revealed the passenger airbag harness connector had a backed-out pin, preventing the ECU from detecting the airbag circuit. Re-crimped the terminal in connector KG10. After ensuring the plug locked securely into position, the fault was cleared.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Atto 3 clock spring loose connection fault after accident repair

✓
After collision repair, the SRS warning light stayed on and the system stored DTC B16101B. Airbag module resistance tested normal. Checking the wiring from the clock spring (spiral cable) to the airbag revealed a loose internal flat cable connection causing an intermittent open circuit. Replaced the clock spring assembly and reconnected the passenger airbag module connector. Ran the SRS self-test, and the fault code cleared. Note: Although the passenger airbag usually does not pass through the steering wheel clock spring, this case involved a rotary connector in the dashboard wiring harness or an unconventional wiring layout.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

Qin series: Damaged passenger airbag connector locking tab causing open circuit

✓
The instrument cluster displayed an airbag fault, accompanied by intermittent self-test failures. Removed the passenger-side dashboard to inspect the airbag module connector and found the CPA (Connector Position Assurance) locking tab damaged, preventing the terminals from fully mating. Wiggling the harness during measurement caused intermittent resistance, confirming an internal break at a bend in the harness. Replaced the airbag harness connector and resoldered the broken wire. Cleared the DTCs and powered on the vehicle multiple times; all tests normal.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

E2 EV dashboard wiring harness worn through, open circuit

✓
2019 BYD E2. SRS light illuminated intermittently after driving on rough roads. Scan tool retrieved code B16101B. Inspection found the passenger airbag harness had chafed at the dash crossmember clip from constant vibration. Insulation wore through, copper strands fractured one after another, causing high resistance. Replaced the dash harness assembly (or repaired locally), fitted anti-chafe sleeves, and rerouted harness away from sharp metal edges.
BYD DTC AI AnalysisFrom Chinese market (translated)

Moisture inside the Qin EV airbag module caused abnormal resistance.

✓
2019 Qin EV: SRS warning light came on during the rainy season with DTC B16101B stored. Inspection found a leak in the seal below the passenger-side A-pillar, allowing water to seep into the dashboard. This caused oxidation of the airbag module connector terminals, and moisture inside the module raised the igniter resistance to 8Ω (exceeding the threshold). After fixing the leak, cleaned the connector terminals and replaced the passenger airbag module. Fault resolved.
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]