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B176F-00

DTC B176F-00 indicates the SRS (Supplemental Restraint System) ECU detects an abnormal electrical connection between the left rear seat belt pretensioner drive circuit and the vehicle power supply (B+) — Atto 8

Safety System

DTC B176F-00 indicates the SRS (Supplemental Restraint System) ECU detects an abnormal electrical connection between the left rear seat belt pretensioner drive circuit and the vehicle power supply (B+).

The pretensioner consists of an igniter and a gas generator, with a normal resistance of 2.0-3.0Ω.

Damaged wiring harness insulation, misaligned connector pins, or an internal pretensioner short circuit cause the ECU to detect an abnormally high circuit voltage (approaching 12V battery voltage) and trigger this DTC.

This fault may result in: 1) Failure of the left rear pretensioner to deploy during a collision, compromising occupant protection. 2) Unintended pretensioner deployment in extreme cases, causing occupant injury. 3) The SRS entering fail-safe mode, disabling all vehicle airbags.

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Cases Logged
Real-World Cases
BYD DTC AI Analysis

BYD Qin EV450 left rear seat rail chafed through wiring harness causing short circuit

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2018 Qin EV450, 42,000 km. Constant airbag warning light. DTC B176F-00. The pretensioner harness under the left rear seat had chafed against the slide rail mounting bolt edge during fore/aft adjustment, wearing through the insulation. The copper core contacted the seat heater power wire (red, 12V constant). Replaced the entire yellow harness from the floor harness to the pretensioner (PN 4C-5823456) and added retaining clips to prevent contact with metal edges. Cleared the DTC; system returned to normal.
BYD DTC AI Analysis

Qin 100 rear seat water ingress caused connector short circuit

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2017 BYD Qin 100. After heavy rain, water pooled in the left rear footwell and wasn't cleaned up. DTC B176F-00 set intermittently. Tore down the B-pillar and found the 2-pin pre-tensioner connector underneath had taken on water. Electrolytic corrosion between the pins produced verdigris, dropping insulation resistance between the power and pre-tensioner drive pins below 200 Ω (normal: infinite). Fix: Cleaned the connector with electronic cleaner, blew it dry, applied conductive grease, replaced the waterproof seal, and cleared the door drain holes to stop it happening again.
BYD DTC AI Analysis

Incorrect wiring of aftermarket seat heater caused fault

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The owner had a heating pad installed on the left rear seat at a third-party workshop. The technician incorrectly spliced the heating pad power feed into the pretensioner wiring harness, mistaking the yellow wiring for the seat power supply. This caused the pretensioner circuit to connect directly to 12V power. The vehicle immediately set code B176F-00 at power-up, and the code could not be cleared. Repair actions: Removed the unauthorised modification, replaced the damaged pretensioner (internal igniter likely damaged by high-voltage impact), restored the factory wiring layout, and explained to the owner that the SRS system prohibits unauthorised modifications.
BYD DTC AI Analysis

Pretensioner internal coil aged and short-circuited

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A Qin EV300 with 80,000 km and no accident history suddenly set DTC B176F-00. Harness visual inspection revealed no damage. With the connector disconnected, the harness side showed no short to power, but the pretensioner terminals measured 0.5Ω to case. Internal igniter coil insulation had degraded and shorted. Replaced the left rear seatbelt assembly (includes pretensioner, PN 4C-6912345). Fault resolved. Note: Pretensioners are single-use components; even without deployment, internal materials can degrade after long-term use.
Other Atto 8 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: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.