AU
B1775-00

This DTC indicates an abnormally low-resistance connection (typically <1 kΩ) between the right rear seat belt pretensioner squib circuit and vehicle chassis ground (GND) — Atto 8

Safety System

This DTC indicates an abnormally low-resistance connection (typically <1 kΩ) between the right rear seat belt pretensioner squib circuit and vehicle chassis ground (GND).

As a pyrotechnic safety device, the pretensioner relies on the SRS ECU to supply a high-current pulse during a collision.

A short to ground causes: 1) abnormal circuit resistance, leading the ECU to register a device fault; 2) potential inadvertent deployment if the short-circuit current reaches the ignition threshold; 3) the SRS system to enter fail-safe mode, disabling the right rear pretensioner and associated seat belt reminder function.

This is a hard fault in the passive safety system that directly affects the integrity of the occupant restraint system.

The B1775-00 fault code on the Atto 8 indicates a high-severity short to ground in the right rear seat belt pretensioner circuit. This can disable that pretensioner and affect SRS safety operation. Common causes include worn wiring near the right B-pillar or floor area, and water-damaged or corroded pretensioner connectors. The recommended fix is to visit an authorised dealer for SRS diagnosis and repair. Typical repair cost data is available.
4
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Wiring harness wear below the right B-pillar: The pretensioner wiring harness routes through the B-pillar trim to the floor. Long-term fore-and-aft seat adjustment or passenger foot movement wears the insulation, causing a short circuit to the metal body.
  • 2Connector water ingress and oxidation: Water accumulation on the rear floor (e.g., from a blocked sunroof drain tube or leaking A/C condensate) corrodes the pins of the pretensioner connector (usually located under the seat or at the base of the B-pillar), forming a short-to-ground path.
  • 3Pretensioner internal fault: Igniter (squib) internal bridge wire insulation failure or damp, conductive propellant causes continuity between the terminals and the housing.
  • 4Post-accident repair issues: During vehicle collision repair, when repairing the B-pillar sheet metal or rerouting the wiring harness, missing retaining clips cause the harness to contact sharp edges, or tools scratch the harness during pretensioner removal and installation.
  • 5Manufacturing defect: Wiring harness insulation batch quality issue causes premature aging and cracking at bend points (such as near the seat hinge).
What To Do
  • 1
    Safe power down: Turn the power switch to OFF, disconnect the 12V battery negative terminal, and wait at least 90 seconds to fully discharge the SRS capacitor. Wear an anti-static wrist strap.
  • 2
    Fault code freeze frame analysis: Connect VDS or a dedicated diagnostic tool, record vehicle status when the fault code occurred (temperature, voltage, mileage), and confirm if the fault is intermittent.
  • 3
    Visual inspection: Remove the right rear B-pillar lower trim panel and seat side trim panel. Check the pretensioner connector (black/yellow marking) for looseness, signs of water ingress, or discolored pins. Inspect the wiring harness at the floor trim strip for wear or exposed copper.
  • 4
    Harness-to-ground insulation test: Disconnect the pretensioner connector. Use a multimeter to measure resistance between the harness side (ECU side) and body ground. Resistance should be >1MΩ. Measure voltage to ground. Voltage should be <1V (to rule out internal ECU short circuit).
  • 5
    Pretensioner unit test: Measure the resistance between the pretensioner terminals (normal: 2.0-4.0 Ω). Measure the resistance between either terminal and the pretensioner metal housing (should be infinite).
  • 6
    Wiring harness repair: If the wiring harness is damaged, repair it with heat-shrink tubing or insulating tape. Install corrugated conduit for protection. Maintain a clearance of at least 20mm from the seat slide rail and body panels. Secure the harness with genuine cable ties.
  • 7
    Component replacement: If the pretensioner has an internal short circuit, replace the right rear seat belt pretensioner assembly (replace the seat belt assembly simultaneously, as the pretensioner is usually integrated into the retractor or anchor base).
  • 8
    System verification: Restore connections, install the trim panel, and connect the battery. Turn the ignition switch ON and confirm the SRS warning lamp turns off after the self-check. Use the diagnostic tool to perform the 'Airbag System Configuration Test' or 'Crash Output Test' (static test mode), clear the fault codes, and perform a road test to verify.
Real-World Cases
BYD DTC AI Analysis

Wiring harness worn by right rear seat rail causing intermittent short circuit

✓
2017 BYD Qin EV300, 80,000 km. Intermittent SRS warning light. Scanner read B1775-00; freeze frame showed rough-road trigger. Inspection revealed the right rear seat rail mounting bolt interfering with the pretensioner wiring harness. Prolonged friction had worn through the insulation, exposing copper wire that contacted the seat frame. Repaired the harness, rerouted the wiring, and installed abrasion-resistant sleeving. Fault resolved.
BYD DTC AI Analysis

Sunroof drain tube detached; water entered and corroded the pretensioner connector.

✓
After driving through water, the SRS warning light stayed on. Retrieved DTC B1775-00. Inspection found the right rear sunroof drain hose connector had detached, letting water run down the A-pillar into the base of the B-pillar. The pretensioner connector pins (located at the floor harness junction) showed severe oxidation and measured only 200 Ω to ground. Cleaned the connector, applied conductive paste, replaced the drain hose connector, and waterproofed the wiring harness. Fault resolved.
BYD DTC AI Analysis

Internal short circuit in pretensioner after accident repair

✓
A BYD Qin 100 repaired following a collision with prior right rear impact. After repairs, DTC B1775-00 was retrieved. Continuity between the pretensioner terminal and housing measured 0.5Ω, indicating the pretensioner internal igniter insulation had been damaged by impact. Replaced the right rear seatbelt pretensioner assembly (including retractor). SRS configuration coding restored normal system operation.
BYD DTC AI Analysis

B-pillar trim improperly installed, crushing wiring harness insulation

✓
The SRS warning light came on the day after window tinting. Customer stated the B-pillar trim was removed during tinting. Inspection found the lower clip on the right rear B-pillar trim misaligned; the panel’s sharp edge crushed the seatbelt pretensioner harness insulation, causing a short to ground. Rerouted and secured the harness, wrapped it with fleece tape to prevent chafing, replaced the damaged clip. Fault cleared.
Other Atto 8 Fault Codes
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.B110A02DTC B110A02 indicates the thermal management master control unit (HVAC ECU) or body control module (BCM) failed to receive valid CAN data frames from the PM2.5 air quality sensor over consecutive communication cycles (typically 500ms per cycle). The sensor typically mounts at the HVAC unit air inlet or behind the glove box and transmits real-time particulate concentration data (unit: μg/m³) to the HVAC controller via the CAN bus. The fault is essentially a communication link layer timeout. Potential causes include physical layer wiring faults, sensor power supply failures, sensor internal MCU lockup, or CAN network topology damage. Although this non-critical fault does not directly affect driving safety, it disables the intelligent air purification strategy and the automatic fresh air/recirculation switching function. In extreme cases, it triggers a thermal management system degraded mode, limiting compressor power or fixing the air flap position.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 overview →
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.