AU
B170E

DTC B170E indicates the SRS (Supplemental Restraint System) control unit detects a short to body ground in the right curtain shield airbag ignition circuit — Atto 8

Safety System

DTC B170E indicates the SRS (Supplemental Restraint System) control unit detects a short to body ground in the right curtain shield airbag ignition circuit.

Specifically, the ACU detects the resistance between the right curtain airbag deployment circuit (typically marked R CSA+ and R CSA-) and ground falls below the threshold (generally <2Ω).

Damaged wiring harness insulation, connector water ingress and corrosion, a shorted inflator inside the curtain airbag module, or a driver transistor breakdown inside the SRS control unit can cause this fault.

Under this fault condition, the circuit protection mechanism may disable the curtain airbag (preventing deployment).

In extreme cases, short-circuit current can trigger unintended deployment, posing a severe safety hazard.

3
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Right A-pillar/C-pillar wiring harness wear: Long-term vehicle use or repeated interior trim removal and installation wears the right curtain airbag wiring harness insulation where it passes through sheet metal holes or retaining clips, causing the copper core to directly contact the vehicle body metal.
  • 2Connector short circuit due to water ingress: A blocked sunroof drain hose or poor sealing allows rainwater to leak into the right roof side rail area, causing the curtain airbag wiring harness connector (usually located above the B-pillar or near the C-pillar) to short between terminals or short to ground.
  • 3Internal fault in the curtain airbag module: A manufacturing defect or aging causes insulation breakdown between the two terminals of the squib inside the right curtain airbag assembly, resulting in a short to ground.
  • 4SRS control unit internal damage: The power transistor or filter capacitor in the ACU internal drive circuit shorts, causing the curtain airbag control terminal to remain continuously grounded.
  • 5Improper repair procedures: During accident repairs or interior modifications, excessively long fixing screws pierce the wiring harness, or incorrect harness routing causes the harness to chafe against the seat bracket or seat belt mounting points.
What To Do
  • 1
    Safety preparation: Set the vehicle to OFF, disconnect the 12V battery negative terminal, wait at least 3 minutes (to fully discharge the SRS capacitor), and wear an anti-static wrist strap.
  • 2
    Fault confirmation: Use VDS or a dedicated BYD diagnostic tool to read the DTC, confirm B170E is an active fault (Active DTC), and record the freeze frame data.
  • 3
    Visual inspection: Remove the right A-pillar trim, headliner front edge, and C-pillar trim. Visually inspect the right curtain airbag wiring harness for obvious damage, burn marks, or liquid ingress.
  • 4
    Circuit measurement: Disconnect the right curtain airbag module connector (yellow waterproof plug). Use a multimeter to measure the resistance to ground at both terminals on the harness side. Normal resistance is ∞ (open circuit). A reading <10Ω indicates a short circuit.
  • 5
    Section isolation: Disconnect the SRS control unit (ACU, usually located under the center console or behind the armrest) connector. Measure the resistance to ground at the wiring harness side of the curtain airbag circuit and at the ACU output terminal to determine whether the short circuit is in the wiring harness or inside the control unit.
  • 6
    Wiring harness repair: If the short circuit is in the wiring harness section, carefully inspect the harness along the right-hand roof rail. Focus on areas passing through sheet metal holes, fixing clips, and vehicle body metal contact points. If damaged, repair the insulation using heat-shrink tubing or tape. Replace the wiring harness assembly if necessary.
  • 7
    Component replacement: If the wiring harness is normal but the resistance between the curtain airbag module terminals is close to 0 Ω, replace the right-side curtain airbag assembly. If the ACU output terminal is shorted to ground, replace the SRS control unit (perform coding configuration simultaneously).
  • 8
    System verification: Reconnect all connectors, connect the battery, power on, and clear the fault code. Perform the 'SRS System Self-check' or 'Configuration and Settings' procedure. Confirm B170E does not return and the instrument cluster airbag warning lamp turns off.
Real-World Cases
BYD DTC AI Analysis

Yuan EV SRS warning light illuminated after driving in rain

✓
After driving through heavy rain, a 2019 Yuan EV displayed an airbag warning light. The DTC read B170E (right side curtain airbag short to ground). Inspection found the right sunroof drain hose had detached, allowing rainwater to enter the A-pillar and corrode the terminals of the right side curtain airbag harness connector (located above the B-pillar), causing a short circuit. The repair: clean the corroded connector terminals, apply conductive protectant, and resecure the drain hose. Fault cleared.
BYD DTC AI Analysis

B170E fault after accident repair on Tang DM

✓
After a right-side collision repair on a 2021 Tang DM, the SRS light stayed on. Diagnosis found active fault code B170E. Inspection revealed that when the technician replaced the right A-pillar trim, a retaining screw was too long and pierced the right curtain airbag harness, causing a short to ground. Repair: Replaced the damaged harness section from ACU to the curtain airbag module, adjusted the screw length, and re-taped the harness. Fault cleared.
BYD DTC AI Analysis

Audio modification causes Song MAX fault

✓
2019 Song MAX. A tool pierced the SRS harness insulation while routing wires through the right A-pillar during roof speaker modification, causing the right curtain airbag circuit to short to the A-pillar metal frame and trigger DTC B170E. The SRS warning light came on immediately upon starting the vehicle the day after modification. Repaired the damaged harness (located in the headliner above the A-pillar) and rerouted the wiring to specification, keeping clear of the SRS harness path. Fault resolved.
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.