AU
B170E-00

DTC B170E-00 indicates an abnormally low-resistance connection between the Right Side Curtain Airbag squib circuit and body ground (GND) — Seal U

Safety System

DTC B170E-00 indicates an abnormally low-resistance connection between the Right Side Curtain Airbag squib circuit and body ground (GND).

In the SRS (Supplemental Restraint System) architecture, two independent wires connect each airbag inflator to the ACU (Airbag Control Unit).

Normal resistance typically ranges from 1.5 to 3.0 Ω.

The ECU identifies a short to ground when it detects circuit resistance below the threshold (typically <1.0 Ω) or abnormal voltage to ground.

This fault causes: 1) The Right Side Curtain Airbag to fail to deploy properly in a collision, resulting in loss of side-impact protection. 2) The SRS to enter fail-safe mode, keeping the instrument cluster airbag warning lamp illuminated and degrading the vehicle safety rating. 3) A risk of unintended deployment in extreme cases due to intermittent wiring contact.

This is a passive safety system hard fault and requires immediate resolution.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Wiring harness wear inside the A-pillar/C-pillar trim panel: Frequent door operation or vehicle vibration wears through the insulation inside the corrugated conduit of the right curtain airbag wiring harness at the A-pillar upper trim panel, roof side rail, or C-pillar. The wire directly contacts the body metal frame, creating a short to ground.
  • 2Connector water ingress and corrosion: A poorly sealed right curtain airbag connector (usually located inside the B-pillar or C-pillar trim) allows water entry during car washing, wading, or in high-humidity environments. This reduces insulation resistance between pins or to ground, creating a short circuit path.
  • 3Airbag module internal fault: The internal bridgewire of the right curtain airbag inflator shorts to the metal housing, or chemical degradation inside the igniter charge increases conductivity. This condition usually produces an abnormally low resistance value (<0.5Ω).
  • 4SRS ECU internal drive circuit fault: Breakdown of the right curtain airbag drive transistor (FET) or a shorted filter capacitor inside the airbag control unit causes a false external short-to-ground detection. Confirm this by disconnecting the airbag module and measuring the resistance to ground at the ECU terminal.
  • 5Third-party modifications: When installing dash cams, ambient lighting, or roof-mounted equipment, fixing screws pierce the SRS wiring harness, or trim panel clips crush and damage the harness. This occurs most frequently after sunroof or headliner removal and installation.
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 90 seconds (allows the SRS backup power supply to fully discharge). Remove the Manual Service Disconnect (MSD) for high-voltage models. Wear an anti-static wrist strap and place a "Do Not Touch" warning sign on the steering wheel and airbag area.
  • 2
    Fault Confirmation and Freeze Frame Analysis: Use a VDS2000 or Launch X431 diagnostic tool to read the fault code. Confirm B170E-00 is a current (active) code, not a history code. Check the freeze frame data for the crash sensor data, vehicle speed, and short-circuit resistance value. Record the ECU software version.
  • 3
    Visual inspection and wiring harness check: Remove the right upper A-pillar trim, headliner edge trim, and C-pillar trim. Inspect the wiring harness corrugated conduit for damage. Check the B-pillar airbag connector (yellow) specifically for sealing condition and terminal corrosion. Measure the wiring harness insulation resistance to ground (>1 MΩ).
  • 4
    Airbag module isolation test: Disconnect the right curtain airbag connector (Note: the shorting clip will short the circuit). At the ECU end, measure the resistance to ground on the wiring harness side: if the resistance is >10kΩ, the fault is inside the airbag module; replace the right curtain airbag assembly. If the resistance remains <1Ω, the fault is in the wiring harness or the ECU.
  • 5
    Section-by-section wiring harness inspection: Upon confirming a wiring harness short circuit, use the 'half-split method' to narrow down the search area. Cut or peel back the wiring harness at the midpoint between the ECU and the airbag module for inspection. Focus on contact points between the wiring harness inside the roof side rail and the body sheet metal. Repair damaged wires and insulate them using double-layer heat-shrink tubing.
  • 6
    ECU verification: If the wiring harness and airbag module are normal, measure the resistance to ground at the SRS ECU right curtain airbag drive terminal. If abnormal, replace the ACU assembly, then perform configuration coding and crash sensor calibration.
  • 7
    System reset and verification: Reconnect all connectors, restore power, clear the fault code, and perform the SRS system self-check (normally completes within 6 seconds after turning the ignition switch ON). Confirm B170E-00 does not return. Use the diagnostic tool to perform the 'airbag simulated deployment test' (requires special tool). Finally, perform a road test to verify the repair.
Real-World Cases
BYD DTC AI Analysis

A chafed wiring harness at the right A-pillar caused an intermittent short circuit in the Qin EV450.

✓
The instrument cluster displayed "Please Check SRS System" when the vehicle arrived. DTC B170E-00 appeared intermittently. Inspection revealed signs the right A-pillar trim panel had been removed (the customer had installed a dashcam). Removing the trim exposed the curtain airbag harness, which had chafed through its insulation at the edge of the A-pillar upper bracket, leaving bare copper touching the body. Vibration during driving caused the short to come and go. Repaired the two damaged wires, re-wrapped with abrasion-resistant corrugated tubing, and adjusted the harness routing to avoid sharp metal edges. Fault resolved.
BYD DTC AI Analysis

Qin 100 right side curtain airbag connector corroded and short-circuited after wading through water.

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2017 BYD Qin 100, DTC B170E-00 active. Vehicle history showed the car had waded through about 40 cm of water three months earlier. Inspection found significant water staining and green corrosion inside the right B-pillar airbag connector (yellow 2-pin). Resistance between pins 3 and 4, and from each pin to ground, was less than 0.5 Ω. Water entered the connector cavity through the sill trim panel during wading. Repair: Replaced the right-side curtain airbag wiring harness assembly (including connector), cleaned the ECU-side connector, and dried the B-pillar cavity. Fault resolved.
BYD DTC AI Analysis

Qin EV300 Airbag Module Internal Short Circuit Misdiagnosis Case

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The vehicle displayed DTC B170E-00. Initial measurement showed the airbag terminals shorted to ground. Replaced the right side curtain airbag but the fault remained. Further inspection revealed rodents had chewed through the wiring harness between the SRS ECU and airbag inside the headliner, causing the live wire to short to body ground. The previous repair had not thoroughly checked the harness routing. Repaired the wiring harness: cut out the damaged section, soldered and insulated the joints, then re-measured insulation resistance – normal. Summary: A short to ground is not necessarily an airbag module fault; always perform a wiring harness isolation test (Disconnect Test) to confirm the fault location.
BYD DTC AI Analysis

Qin 80 ACU drive circuit fault after accident repair

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Accident repair (right side impact). After replacing the right curtain airbag and B-pillar trim, DTC B170E-00 remained active. Disconnected the airbag module; measured 0.2Ω short to ground at the ECU terminals, still present. Inspected and confirmed no wiring harness damage. Determined the right curtain airbag drive circuit inside the SRS ECU failed from overcurrent damage during the collision, causing continuous low-impedance output. Replaced the airbag control unit (ACU), performed VIN writing, sensor calibration, and configuration matching with VDS. Fault cleared.
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.