AU
B16F0

This DTC indicates an abnormally low-resistance connection between the Supplemental Restraint System (SRS) Right Rear Impact Sensor signal circuit and body ground — Seal U

Safety System

This DTC indicates an abnormally low-resistance connection between the Supplemental Restraint System (SRS) Right Rear Impact Sensor signal circuit and body ground.

In the BYD SRS architecture, impact sensors utilize a dual-axis accelerometer design, transmitting a 0-5V analog voltage signal to the Airbag Control Unit (ACU) via hardwire.

A short to ground continuously pulls the signal line voltage down to <0.5V (normal static voltage is approximately 2.5V).

The ACU sampling circuit detects this abnormal voltage level and triggers the DTC.

This fault forces the SRS into fail-safe mode, disabling the right rear side airbag and curtain airbag deployment while illuminating the airbag warning lamp.

Because the short circuit can occur anywhere in the wiring harness, excessive short-circuit current (>2A) risks burning out the internal ACU drive circuit.

This single-point failure directly compromises the vehicle's side-rear collision detection capability and, in extreme cases, prevents airbag deployment during a collision.

The B16F0 fault code on the Seal U indicates a short to ground in the SRS right rear impact sensor signal circuit. This is a high-severity fault because it can disable the right rear side and curtain airbags and turn on the airbag warning light. Common causes include worn wiring near the C-pillar or rear seat bracket, or water-damaged sensor connector pins. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Long-term vibration at the C-pillar or rear seat mounting bracket wears the right rear impact sensor wiring harness. Damaged insulation causes the signal wire to contact body ground. Commonly seen on vehicles with >50,000 km.
  • 2Degraded sealing ring or loose retaining clip on the sensor connector (usually located inside the right rear quarter panel). Water ingress after washing or wading causes electrolytic corrosion between the pins, creating a short-to-ground path.
  • 3External impact or electrical overstress typically causes an internal breakdown of the crash sensor ASIC chip, creating a short circuit between the signal output terminal and the metal housing (ground).
  • 4During rear collision repairs, incorrect harness routing allows trim panel clips to crush the wiring harness or metal clamps to cut through the harness insulation, causing a hidden short circuit.
  • 5Damaged ADC channel in the SRS control unit (ACU) internal sampling circuit or reference voltage drift causes a false sensor short-to-ground report (rule out through cross-checking).
What To Do
  • 1
    Use VDS2000 or the dedicated BYD diagnostic tool to read fault codes. Confirm B16F0 is a current fault (Current DTC), not a history fault. Record environmental parameters from the freeze frame data, such as vehicle speed and temperature.
  • 2
    Perform the safe power-down procedure: Disconnect the 12V battery negative terminal and wait at least 90 seconds for the SRS capacitor to fully discharge. Do not operate any electrical equipment during this time.
  • 3
    Remove the right rear C-pillar trim panel and rear seat side trim panel. Locate the right rear impact sensor (usually marked 'SIS RR' or 'SENSOR, SIDE IMPACT REAR RIGHT'). Confirm the part number is a genuine BYD part (such as the 5A-XXXXXX series).
  • 4
    Visual inspection: Check the sensor body for physical damage. Inspect the connector for obvious signs of water ingress (white powdery corrosion) and bent or backed-out pins. Check the corrugated wiring harness conduit for damage where it passes through the sheet metal hole.
  • 5
    Disconnect the sensor connector and use a digital multimeter to measure the resistance between the sensor-side signal pin (usually Pin 2) and the sensor housing. Normal resistance is open circuit (>10MΩ). If continuity exists (<1Ω), replace the sensor assembly.
  • 6
    Measure the insulation resistance of the harness-side signal wire to ground: >1MΩ. If the resistance is too low, troubleshoot along the harness routing using the half-split method. Focus inspection on the harness protective sleeve for wear-through at the floor crossmember and seat slide rail mounting points.
  • 7
    If the wiring harness insulation is normal, turn the ignition ON and measure the voltage at the sensor signal pin on the ACU side. The voltage must be the 5V reference voltage (±0.25V tolerance). If the voltage is 0V, an internal ACU short circuit may exist. Measure the resistance from this pin to ground to confirm.
  • 8
    When repairing the wiring harness, apply a double layer of high-temperature tape (125°C grade) and install a rubber grommet at the pass-through hole. When replacing the sensor, tighten it to the standard installation torque (usually 8-10 N·m). Verify the sensor makes tight contact with the vehicle body metal surface to accurately transmit vibration.
  • 9
    Reconnect all connectors (confirm the locking 'click'), reinstall the trim panels, and connect the battery. Use the diagnostic tool to clear the fault code and perform the 'SRS system self-check' procedure.
  • 10
    Perform functional verification: Enter the data stream and read 'Right Rear Impact Sensor Status'. Lightly tap the right rear quarter panel with a rubber mallet to simulate collision vibration. Confirm the sensor output voltage changes accordingly (2.5V→0V or 5V pulse) and the diagnostic tool generates no new fault codes.
Real-World Cases
BYD DTC AI Analysis

Corroded sensor connector on water-wading vehicle caused short circuit

✓
A 2019 BYD Yuan EV with 42,000 km on the clock came in with the airbag warning light permanently on. Scanning revealed current fault code B16F0. Inspection found visible water staining inside the connector of the right rear impact sensor, located at the lower C-pillar. Pins 1 (earth) and 2 (signal) showed green copper corrosion, and resistance between them measured only 0.3 Ω. Investigation traced the cause to the vehicle wading through water deeper than the door sill one month earlier, allowing water to seep in through the wiring harness grommet. Replaced the sensor (internally corroded), cleaned the connector with electronic contact cleaner, fitted a new waterproof seal, and applied waterproof sealant to the sensor mounting base. This cleared the fault. Advised the owner to check the sealing condition of other low-mounted sensors.
BYD DTC AI Analysis

Wiring harness pinched after accident repairs, causing intermittent short

✓
A 2021 BYD Tang developed a B16F0 DTC one week after an accident repair to the left rear quarter panel. Service history showed the left rear wing had been replaced. Investigation revealed that technicians had incorrectly routed the right rear impact sensor wiring harness (which runs parallel to the left rear side harness) beneath the seat mounting bracket. The metal bracket edge cut through the corrugated tubing and crushed the wire insulation, causing the signal wire to short to ground against the bracket. The pinch point was concealed inside the seat rail, making it hard to catch during a routine visual inspection. Repair steps: Released the seat mounting bolts, removed the damaged harness, cut out the damaged section (approximately 15 cm), fused in replacement wiring by soldering (twist connections prohibited), insulated with double-layer heat shrink tubing, and rerouted the harness away from sharp metal edges. The fault was completely resolved.
BYD DTC AI Analysis

Thermal breakdown of the sensor's internal ASIC chip

✓
2019 BYD Song MAX, 68,000 km. Intermittent airbag warning light, DTC B16F0 (intermittent). Initial inspection: wiring harness insulation normal, connectors normal. Used an oscilloscope to monitor the sensor signal line; found intermittent short-to-ground pulses on rough roads. Disassembled the sensor; found slight burn marks on the bottom of the MEMS accelerometer chip on the internal PCB. Determined that long-term high-temperature exposure (sensor mounted on C-pillar metal panel; summer cabin temperatures exceed 70°C) caused breakdown of the chip's internal signal conditioning circuit. Repair: Replaced right rear impact sensor (part number varies by production date). Installed a heat insulation pad (included in OEM repair kit) between the new sensor and body mounting surface to keep sensor operating temperature below 85°C.
BYD DTC AI Analysis

Aftermarket sensor compatibility issue

✓
2020 Qin petrol variant. After an unauthorised repair shop replaced the right rear impact sensor, DTC B16F0 appeared. Multimeter testing revealed a fixed resistance of approximately 200 Ω between the signal output terminal and housing on the aftermarket sensor; a genuine sensor should read high impedance. The cause was an internal circuit design defect in the aftermarket part—the signal output stage lacked complete isolation. Solution: Replaced with a genuine BYD sensor (verify part number via VDS), cleared the fault code, and the fault disappeared. Impact sensors must be genuine OEM parts. Aftermarket units can cause false triggering or functional failure due to mismatched electrical parameters.
BYD DTC AI Analysis

Wiring harness sheath wear caused intermittent short circuit

✓
2019 Yuan, 55,000 km. Airbag warning light illuminated intermittently. DTC B16F0 status: History/Intermittent. Inspection found the right rear collision sensor harness chafing where it passes through the floor-to-C-pillar junction. Repeated trunk opening and closing flexed the harness repeatedly, wearing through the corrugated tubing and abrading the wire insulation. This caused intermittent contact with the body panel when the vehicle vibrated. Insulation resistance tested with a megohmmeter showed normal readings at rest, but resistance dropped to <100 Ω when bending the harness. Repair: Cut out the worn harness section (approx. 20 cm), re-routed the wiring, added securing clips to prevent body panel contact, and fitted braided sleeving for extra protection.
Other Seal U Fault Codes
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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173712DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Common problems reported for Seal U →Seal U 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.