AU
B1770-00

DTC B1770-00 indicates the SRS (airbag) control module detects the right rear seat belt pretensioner circuit resistance is 0 Ω or close to 0 Ω — Atto 8

Safety System

DTC B1770-00 indicates the SRS (airbag) control module detects the right rear seat belt pretensioner circuit resistance is 0 Ω or close to 0 Ω.

Normally, the seat belt pretensioner acts as a pyrotechnic actuator with a standard squib resistance between 2.0-5.0 ohms.

A resistance of 0 indicates a hard short in the circuit.

Possible causes include an internal short in the pretensioner squib, a wiring harness short to body ground or power, or an internal short in the connector.

This fault causes the SRS system to determine the pretensioner has failed.

During a collision, the right rear seat belt pretensioner will not deploy, severely compromising the occupant restraint system's effectiveness.

The fault also illuminates the instrument cluster airbag warning lamp and may inhibit the entire airbag system.

4
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Right rear seat belt pretensioner internal igniter short circuit: Aging, moisture ingress, or manufacturing defects cause insulation failure between the internal squib terminals, resulting in a short circuit.
  • 2Wiring harness short to ground or power: Long-term bending, wear, or accident crushing damages the B-pillar wiring harness insulation, causing a short to the vehicle body metal or power wire.
  • 3Connector fault: Water ingress, corrosion, deformed pins, or foreign objects in the right rear seat belt pretensioner connector (usually located below the B-pillar or under the seat), causing a short circuit between terminals.
  • 4SRS ECU internal detection circuit fault: Airbag control module internal monitoring circuit malfunction triggers a false short circuit fault (relatively uncommon).
  • 5Improper repair work: During recent removal and installation of the B-pillar, rear door, or seat, a screw pinched the wiring harness, retaining clips were damaged, or a tool accidentally cut the wiring harness insulation.
What To Do
  • 1
    Safety preparation: Set the vehicle to OFF, disconnect the 12V low-voltage battery negative terminal, and wait at least 90 seconds (2 minutes for some models) to fully discharge the SRS capacitor and prevent accidental deployment.
  • 2
    Locate the component: Remove the right rear B-pillar lower trim panel. Find the right rear seat belt pretensioner and its yellow dedicated connector (usually featuring a short-circuit protection tab).
  • 3
    Initial inspection: Visually inspect the connectors and wiring harness for obvious damage, signs of water ingress, burn marks, or corrosion. Verify the connectors are fully seated.
  • 4
    Resistance measurement: Disconnect the pretensioner connector. Use a digital multimeter to measure the resistance across the pretensioner terminals (do not set to continuity/buzzer mode to prevent trigger current). Normal resistance is 2.0-5.0Ω. A reading of 0-0.5Ω confirms an internal short circuit in the pretensioner.
  • 5
    Wiring harness insulation check: With the connector disconnected, measure the resistance between the harness-side terminal and body ground, and between the terminal and the 12V power supply. Both readings must be infinite (OL). Continuity indicates a short circuit in the wiring harness. Troubleshoot and repair.
  • 6
    Cross-check: If the pretensioner tests normal, substitute a known-good pretensioner and test, or measure the resistance of the adjacent seat pretensioner for reference.
  • 7
    Fault repair: If the pretensioner has a short circuit, replace the right rear seat belt assembly (the pretensioner is usually unavailable separately). If the wiring harness has a short circuit, repair or replace the wiring harness. Route the harness correctly, secure it firmly, and avoid interference.
  • 8
    System reset: Reconnect all connectors (listen for a click), connect the battery, use the BYD dedicated diagnostic tool (VDS) to clear the fault code, perform the SRS system self-check, and verify B1770-00 does not return and the airbag warning light turns off.
Real-World Cases
BYD DTC AI Analysis

Water entered the B-pillar after fording, causing the connector to short-circuit.

✓
A 2017 Qin EV300 showed a constant airbag warning light after driving through floodwater during heavy rain. Retrieved DTC B1770-00. Removed the trim below the right rear B-pillar and found the pretensioner connector contained obvious water traces and green copper corrosion. Conductive debris shorted the terminals. Cleaned the terminals with alcohol, blew them dry, applied electrical contact protectant, and reinstalled the connector. Fault resolved. Check door seals and drain holes to prevent further water ingress.
BYD DTC AI Analysis

Pretensioner internal squib shorted from aging

✓
A 2018 BYD Qin EV450 with 60,000 km and no accident history suddenly displayed the airbag warning light. The scan tool showed B1770-00. After disconnecting the right rear pretensioner connector, direct measurement of the pretensioner read 0.3Ω (normal 2-5Ω), confirming an internal squib short. Replaced the right rear seatbelt assembly (including pretensioner), cleared the fault code, and the system self-test passed. Moisture in the pyrotechnic charge or insulation degradation after long-term use caused the failure.
BYD DTC AI Analysis

Wiring harness pinched and shorted after accident repair

✓
A 2017 Qin 100 underwent bodywork and paint on the right rear door. Three days after delivery, B1770-00 set. Inspection found the B-pillar interior trim panel mounting screw pinched the pretensioner harness during installation, damaging the insulation. The wires contacted the body metal, causing a short to ground. Rerouted the harness to avoid the screw mounting points, repaired the damage with insulation tape and heat-shrink tubing, and resolved the fault. Protect wiring harnesses during any B-pillar repair work.
BYD DTC AI Analysis

Connector short-circuit protection tab failed, causing false trouble code.

✓
A Qin EV300 set DTC B1770-00 after the right rear seat was removed and reinstalled. The pretensioner connector’s internal shorting bar had mechanically deformed and failed to spring open while disconnected, keeping the circuit shorted even when plugged in. A new pretensioner connector (with wiring harness plug) restored normal resistance and cleared the fault. Handle connectors carefully during removal and installation to avoid damaging the internal short-circuit protection.
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: Official This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.