AU
B177412

DTC B177412 indicates the Supplemental Restraint System (SRS) detects an abnormally low-resistance connection between the right rear seat belt pretensioner drive circuit and the vehicle positive power supply (B+), indicating a short to power — Seal U

Safety System

DTC B177412 indicates the Supplemental Restraint System (SRS) detects an abnormally low-resistance connection between the right rear seat belt pretensioner drive circuit and the vehicle positive power supply (B+), indicating a short to power.

The normal pretensioner igniter resistance is approximately 2.0-3.0Ω.

The SRS ECU monitors circuit current and voltage to determine component status.

If damaged wiring harness insulation causes the power wire (typically red/yellow) to contact the pretensioner drive wire, the ECU detects an abnormally high voltage (approaching the 12V battery voltage) and triggers this DTC.

This fault causes the SRS to disable the right rear seat belt pretensioner circuit.

During a collision, the pretensioner may fail to deploy and tighten the seat belt, creating a severe safety hazard.

Additionally, the short to power creates a risk of unintended pretensioner deployment under extreme conditions.

The system therefore classifies this as a severe fault (Level 3) and prohibits continued vehicle operation.

Note: Repair practices for certain vehicle models may define this DTC as a seat ventilation system control circuit fault.

Verify the definition against the specific vehicle configuration.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Wiring harness mechanical damage: The pretensioner harness inside the right B-pillar trim panel or under the seat chafes against a body metal edge or seat slide rail, damaging the insulation and shorting the power wire to the pretensioner drive wire.
  • 2Connector water ingress and corrosion: Wading, improper car washing, or aging seals allow water to enter the right rear seat belt pretensioner connector (usually located at the base of the B-pillar or under the seat), causing an electrolytic short circuit between the pins.
  • 3Pretensioner internal fault: Igniter internal bridge wire shorted to metal housing (usually resulting from manufacturing defects, physical impact, or residual stress from pretensioner deployment in a previous accident).
  • 4Improper repair work: during previous B-pillar repairs, carpet replacement, or seat removal, screws or clips pierced the wiring harness, or incorrect securing positions compressed the harness against the power supply wiring.
  • 5SRS control module internal fault: MOSFET or monitoring chip failure in the ECU internal pretensioner drive circuit causes a false code (confirm by disconnecting the pretensioner connector and measuring voltage at the ECU terminals).
What To Do
  • 1
    Safe power-down: Turn off the ignition switch, disconnect the 12V battery negative terminal, and wait at least 3 minutes to allow the SRS capacitor to discharge fully and prevent accidental airbag deployment. Wear an anti-static wrist strap.
  • 2
    Visual inspection: Remove the right B-pillar lower trim panel and the right rear door sill trim panel. Check the pretensioner connector (usually marked 'R2 Pretensioner' or 'RR SBPT') for looseness, water ingress, corrosion, or signs of burning.
  • 3
    Circuit isolation test: Disconnect the SRS ECU connector. Use a multimeter to measure the voltage between the pretensioner drive pin and ground (should be 0 V). A battery voltage reading confirms the wiring harness is shorted to power. Measure the pretensioner resistance (normal: 2.0-3.0 Ω; 0 Ω or infinite indicates a short circuit).
  • 4
    Sectional fault tracing: Disconnect the pretensioner harness connector at the middle of the B-pillar. Separately measure the resistance and check for a short to power in the ECU-to-connector and connector-to-pretensioner segments to pinpoint the short circuit location.
  • 5
    Repair verification: After repairing the damaged wiring harness (insulate with heat-shrink tubing and reroute to avoid interference points) or replacing the pretensioner assembly, reconnect the battery. Use VDS2000/VDS2100 to clear the fault codes. Perform the 'SRS system self-diagnosis' and 'seat belt pretensioner function test'. Confirm no fault codes exist and the resistance value is within the normal range.
Real-World Cases
BYD DTC AI Analysis

BYD Tang DM B177412 Fault — Front Seat Ventilation System Malfunction

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Symptoms: Dashboard displayed "Seat Ventilation System Fault" warning. Front seat ventilation inoperative; system auto-shutoff when activated. Diagnosis: VDS scan retrieved DTC B177412 (front seat ventilation fan control circuit short to ground). Fan supply voltage measured 0V (normal: 12V). Removed driver's seat and found fan connector harness pinched and worn by seat slide rail, with positive wire shorted to seat frame. Resolution: Repaired damaged wire insulation with heat-shrink tubing. Rerouted harness and added securing clips to prevent slide rail contact. Fitted protective sleeving at contact point. Cleared fault codes; function returned to normal.
Original source ↗
BYD DTC AI Analysis

BYD Han EV B177412 — Seat memory failure with ventilation fault

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Symptoms: 2021 Han EV Flagship. Driver seat memory function intermittently fails, seat ventilation shuts off automatically after 5 minutes, instrument panel displays "Please check seat system". Diagnosis: VDS scan showed DTCs B177412 (seat ventilation control circuit fault) and B177512 (seat memory module communication fault). Inspection under the driver seat found the GJK2 connector (integrated seat memory and ventilation module connector) loose. Voltage measurement showed IGN power dropping to 9.8V during the fault. Traced to wiring harness under the seat interfering with a body mounting clip, causing internal copper wire breakage and poor contact. The memory module connector pins were also oxidized. Repair: Replaced the damaged IGN power wiring harness and rerouted it to avoid the interference. Cleaned the memory module connector pins and applied conductive paste. Replaced the GJK2 harness connector assembly. Updated the seat control module software to V2.1. Tested continuously for 30 minutes with no faults.
Original source ↗
BYD DTC AI Analysis

BYD Song PLUS DM-i B177412 Fault - Front Passenger Seat Ventilation Malfunction

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Symptoms: Front passenger seat ventilation worked normally on level 2, but immediately triggered a fault and stopped working when switched to level 3 (maximum), requiring a vehicle restart to resume operation. Diagnosis: Retrieved DTC B177412 (front passenger seat ventilation fan drive circuit overcurrent). Live data analysis revealed the fan current spiked to 4.8A on level 3 (normal maximum 3.2A). Removed the seat and found the fan impeller rubbing against the housing. Measured motor resistance at 1.2Ω (below the standard 1.8-2.5Ω range), indicating a partial internal short in the motor windings. A severely clogged filter also increased motor load. Solution: Replaced the front passenger seat ventilation fan assembly (part number SA3E-6804019). Cleaned the ventilation ducts and filter. Installed a sponge filter layer at the fan intake. Used the VDS to execute the 'seat ventilation system self-learning' function to calibrate the fan speed levels. Tested all levels and verified normal current draw (level 1: 1.2A, level 2: 2.1A, level 3: 2.9A).
Original source ↗
BYD DTC AI Analysis

BYD Seal B177412 — Rear Seat Ventilation System Fault

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Symptoms: 2022 Seal 700km variant. Rear seat ventilation shuts off automatically 10 seconds after activation; the center display shows "Rear Seat Function Limited". Front seat ventilation works normally. Diagnosis: VDS read DTC B177412 (Rear Seat Ventilation Control Circuit Short to Ground). The rear seat ventilation uses a standalone Rear Seat Control Module (RSCM) on the LIN bus. Measured 0V at the fan power supply; fuse F4/15 (15A) was intact. No IGN power at the RSCM. Traced the fault to wiring beneath the rear carpet soaked by a beverage, causing corrosion and an open circuit. Solution: Replaced the Rear Seat Control Module (RSCM) and damaged wiring harness connectors. Cleaned corroded ground point G408 and applied anti-corrosion treatment. Re-wrapped the harness with waterproof tape and installed a water barrier pad. Replaced the ventilation fan due to insulation degradation from water ingress. Used VDS to write the vehicle configuration code and performed system configuration.
Original source ↗
BYD DTC AI Analysis

BYD Denza D9 B177412 Fault - Second-row seat ventilation inoperative

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Symptoms: 2023 Denza D9 DM-i AWD Flagship. Left second-row aviation seat ventilation failed; right side normal. Button unresponsive, no display icon, but heating works. Diagnosis: Fault code B177412 (left rear seat ventilation control circuit fault). The Denza D9 aviation seat ventilation fan sits inside the backrest. Measured 12V fan power supply – normal. PWM control signal line had no voltage. Checked Seat Control Module (SCU) and found water ingress traces (from wiping with wet towel). Confirmed output stage MOSFET shorted; module lost drive capability. Direct power test confirmed fan operates normally. Resolution: Replaced left second-row SCU (part number SC2E-6804010A). Installed external waterproof cover over the module as repair improvement. Recalibrated seat memory positions (data lost after replacement). Tested all three ventilation speeds and AC linkage – all normal.
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.