AU
B1676-00

DTC B1676-00 indicates the airbag control module (SRS ECU) detects a communication interruption or circuit fault in the Left Rear Side Impact Sensor (LR-SIS) — Seal U

Safety System

DTC B1676-00 indicates the airbag control module (SRS ECU) detects a communication interruption or circuit fault in the Left Rear Side Impact Sensor (LR-SIS).

The sensor typically mounts on the vehicle's left rear side panel, inside the C-pillar trim panel, or on the side of the rear seat to monitor collision acceleration at the left rear of the vehicle.

The ECU sets this fault code when it detects an open circuit, a short circuit, or internal sensor resistance outside the calibrated range (typically 2.0–3.0 kΩ, depending on the vehicle model).

This SRS communication link fault may prevent the side airbags and side curtain airbags from deploying correctly during a side impact.

It can also force the entire airbag system into a degraded protection mode, severely compromising passive safety performance.

5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Sensor connector loose, oxidized, or affected by water ingress: The left rear side impact sensor mounts in the vehicle side panel. Wading, car washing, or damp environments can oxidize or corrode the plug, and vehicle vibration can loosen it.
  • 2Harness wear or breakage: Rear seat adjustment, crushing by objects, or aftermarket audio/soundproofing installation may pinch or cut the harness located in the C-pillar or under the seat, causing an open circuit or intermittent poor contact.
  • 3Sensor fault: Damage to the internal piezoelectric element or processing circuit causes abnormal resistance values or no signal output.
  • 4Poor contact at SRS ECU terminal: loose connection at airbag control module connector, backed-out pins, or ECU internal monitoring circuit fault.
  • 5Electromagnetic interference or abnormal voltage: Low vehicle battery voltage or electromagnetic interference from installed aftermarket electronic equipment distorts the sensor communication signal.
What To Do
  • 1
    Safety preparation: Switch the vehicle OFF, disconnect the low-voltage battery negative terminal, and wait at least 90 seconds to fully discharge the SRS system capacitors and prevent accidental airbag deployment.
  • 2
    Locate the sensor: Refer to the workshop manual to remove the left rear side trim panel or lower C-pillar trim panel. Find the left rear side impact sensor (usually marked 'SIS LR' or similar).
  • 3
    Visual inspection: Verify the sensor connector is fully seated and the locking tab is intact. Inspect the inside of the connector for water stains, oxidation, or foreign objects. Inspect the wiring harness for signs of abrasion, crushing, or breaks.
  • 4
    Resistance measurement: Disconnect the sensor connector and use a multimeter to measure the sensor body resistance (standard value is usually 2.0-3.0 kΩ; refer to the vehicle manual for specifics). If the resistance is 0 or infinite, replace the sensor.
  • 5
    Circuit continuity test: Measure wiring harness continuity between the sensor connector and the SRS ECU to check for open circuits. Measure the insulation resistance of the wiring harness to ground and power supply to check for short circuits.
  • 6
    Repair and replacement: Clean the oxidized connector and apply conductive grease. Repair the damaged wiring harness (solder and insulate with heat-shrink tubing). Replace with a genuine sensor if necessary.
  • 7
    System reset: Reconnect all connectors and the battery negative terminal. Use the VDS2000 or Launch X431 diagnostic tool to clear fault codes. Run the 'SRS system self-check' and 'crash sensor zero-point calibration' procedures. Confirm the warning light turns off and no current fault codes remain.
Real-World Cases
BYD DTC AI AnalysisFrom Chinese market (translated)

Left rear quarter panel wiring harness wear on a BYD Qin Pro DM causing B1676-00

✓
Symptoms: Airbag warning light constantly illuminated on the instrument panel. DTC B1676-00 stored (left rear side impact sensor disconnected). Diagnosis: Inspected the sensor connector at the left rear C-pillar — connection OK. Measured sensor resistance: 2.3kΩ (normal). Resistance fluctuated when wiggling the wiring harness. Peeled back the corrugated tubing and found the harness had chafed against the body metal edge, wearing through the insulation and causing an intermittent open circuit in the copper wire. Solution: Repaired the damaged harness (resoldered connections and applied heat shrink tubing), rerouted the harness away from sharp edges, and wrapped it with foam to prevent abrasion. Cleared the fault code; system returned to normal.
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Song MAX aftermarket audio modification caused sensor communication fault

✓
Symptoms: Vehicle displayed "Check SRS System" after starting, with DTC B1676-00 present. Diagnosis: Recent audio system modification involved removal of the left rear quarter trim panel. Found the sensor connector not fully seated during the modification, with a broken locking tab causing an intermittent connection. Also found the added subwoofer harness tied too tightly to the sensor harness, causing signal interference. Resolution: Replaced the damaged sensor connector by splicing in an OEM connector. Rerouted the wiring to ensure at least 20 cm separation from the audio harness. Performed sensor configuration learning using the diagnostic tool. Fault resolved.
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Tang DM sensor connector oxidised after wading

✓
Symptoms: After driving through heavy rain and waterlogged roads, the airbag warning light illuminated intermittently, and fault code B1676-00 appeared sporadically. Diagnosis: Found water stains and green oxidation inside the left rear side impact sensor connector, causing high contact resistance (measured 5.6kΩ, outside normal range). Traced the cause to a previous window tinting job that left the C-pillar waterproof membrane improperly sealed. Fix: Cleaned the connector terminals thoroughly with precision instrument cleaner and fine sandpaper, applied conductive grease, replaced the waterproof sealing ring, and resealed the waterproof membrane. The fault has not returned.
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD e5 EV sensor body damaged

✓
Symptoms: Instrument cluster displayed airbag system fault. Code B1676-00 was current and could not be cleared. Diagnosis: Measured voltage at the sensor connector (normal: 5V reference) — voltage normal. Disconnected sensor and measured internal resistance: infinite (open circuit). Normal resistance: 2.0–3.0 kΩ. Checked wiring harness continuity: normal, no short or open circuits. Determined sensor internal piezoelectric element had failed. Resolution: Replaced left rear side impact sensor with genuine part, performed SRS system configuration, ran system self-test — passed.
Original source ↗
BYD DTC AI AnalysisFrom Chinese market (translated)

BYD Song Pro sensor not connected after accident repair

✓
Symptoms: The vehicle was scraped on the left rear side. After repair at a workshop, the airbag warning light stayed on with DTC B1676-00. Diagnosis: The accident repair involved body work on the left rear quarter panel. Inspection found the sensor connector left unplugged (the technician forgot to reconnect it). Fresh paint covered the ground point on the sensor mounting bracket, causing a poor ground connection. Fix: Reconnected the sensor connector and verified the lock tab was fully seated. Sanded the paint off the ground point to restore bare metal contact. Tightened the sensor mounting bolts to 8–10 N·m. Cleared the fault code and the system operated normally.
Original source ↗
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. Sources: [1]