AU
B16E700

DTC B16E700 indicates the airbag system (SRS) detects a communication interruption or physical disconnection of the Middle Rear Impact Sensor — Seal U

Safety System

DTC B16E700 indicates the airbag system (SRS) detects a communication interruption or physical disconnection of the Middle Rear Impact Sensor.

This sensor, typically located on the inner rear bumper reinforcement or lower C-pillar, monitors rear-end collision acceleration.

A "not connected" status means the SRS control unit receives no valid signal from the sensor, typically indicating an open circuit or high-resistance condition.

The system determines the sensor circuit is open, the connector is detached, or the sensor has internal damage.

This fault causes the SRS to lose accurate rear-end collision monitoring capabilities.

It may force the airbag control unit into a degraded protection mode, disable specific airbag functions, or illuminate the airbag warning lamp continuously, severely compromising passive safety system reliability.

The B16E700 fault code on the Seal U indicates the SRS airbag system cannot communicate with the middle rear impact sensor, meaning it may be disconnected or have an open circuit. Severity is medium because rear crash detection and some airbag functions may be reduced. Common causes include a loose or corroded rear bumper harness connector or an internally damaged sensor. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Rear bumper wiring harness connector loose or disconnected: Vibration from driving on rough roads can loosen the crash sensor plug inside the rear bumper. Alternatively, driving through water can cause pin corrosion and oxidation due to poor sealing, resulting in poor contact.
  • 2Internal open circuit in the sensor body: Physical impact to the center rear impact sensor (such as a minor rear-end collision or reversing collision) or long-term aging damages the internal piezoelectric element or circuit board, resulting in an open circuit.
  • 3Harness breakage or wear: Repeated bending or friction against other components breaks the copper wires in the harness connecting the main body harness to the rear bumper as it passes through the rear panel and floor trim strip, causing an open circuit.
  • 4Poor ground point: A loose, oxidized, or paint-covered sensor ground point (usually located on the rear floor or inside the C-pillar) creates excessive circuit resistance, causing the SRS module to falsely detect the sensor as disconnected.
  • 5SRS control unit connector issue: A loose control unit connector under the center console or in the front compartment causes poor contact at a specific pin (center rear crash sensor signal wire).
What To Do
  • 1
    Fault confirmation and freeze frame analysis: Use VDS2000 or a BYD dedicated diagnostic tool to read the fault codes, confirm B16E700 is a current fault (Active), record the freeze frame data (ambient temperature and vehicle status), and check for other SRS-related fault codes (such as B16E800 short to ground).
  • 2
    Visual inspection and connector check: Remove the rear bumper trim panel and locate the center rear impact sensor (usually in the middle or left side of the rear crash beam). Verify the sensor connector is fully seated. Verify the connector waterproof seal is intact. Check the terminals for green oxidation, backed-out pins, or deformation.
  • 3
    Circuit continuity test: Disconnect the 12V battery negative terminal. Disconnect the SRS ECU connector and sensor connector. Use a multimeter to measure sensor wiring harness continuity between the ECU and sensor ends. Resistance must be less than 1 Ω. Measure signal wire insulation to ground and power to verify no short circuits.
  • 4
    Sensor body inspection: Measure the sensor body resistance with a multimeter (normal value is typically 500Ω-10kΩ; refer to the workshop manual for exact specifications). A reading of infinity (OL) indicates an internal open circuit. Lightly tap the sensor housing and observe if the resistance value fluctuates to verify the piezoelectric element condition.
  • 5
    Ground point check: Check the sensor ground bolt on the left side of the rear floor (usually near the rear seat mounting point). Clean the contact surface and measure the ground resistance; it must be less than 1Ω. If necessary, sand the surface and retighten the bolt.
  • 6
    Replacement verification and system reset: If the sensor is faulty, replace it with a genuine part (part number must match the vehicle model, e.g., E2/Qin EV common part). Apply conductive paste during installation. Connect all connectors, reconnect the battery, and use the diagnostic tool to clear the fault code. Execute the 'SRS system self-check' procedure. Confirm B16E700 does not reappear and the airbag warning light turns off.
Real-World Cases
BYD DTC AI Analysis

Centre rear impact sensor communication fault after water wading

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A 2019 BYD Qin EV had the airbag warning light stay on after driving through floodwater in heavy rain. A diagnostic scan retrieved DTC B16E700. Technicians found water had reached the rear bumper level. After removing the rear bumper, they found obvious water stains inside the centre rear impact sensor connector – the pins were oxidised and black. Repair: cleaned the connector thoroughly with electronic contact cleaner, dried it, applied waterproof silicone grease, replaced the sensor (water-damaged internally), and wrapped the connector with waterproof tape. Once the fault was cleared, the technician advised the owner to check the rear bumper seal for deterioration.
BYD DTC AI Analysis

Sensor not plugged in after accident repair triggered a warning.

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After a minor rear-end collision, a BYD E2 had its rear bumper replaced at a third-party workshop. The owner then noticed the airbag warning light on the instrument panel and brought the vehicle to our shop. We found current fault code B16E700. Our inspection revealed the technician had not fully seated the center rear impact sensor harness connector during bumper installation. The connector lock did not click into place, and the plug eventually worked loose and disconnected due to vibration while driving. We reconnected the sensor plug and confirmed the locking tab engaged securely. We cleared the fault code using a diagnostic tool and ran an SRS cyclic test. This resolved the fault. We recommend standardizing the SRS self-check procedure after accident repairs.
BYD DTC AI Analysis

Wiring harness aging and breakage causing intermittent fault

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A 2020 BYD E3 had an intermittent airbag warning light while driving. The diagnostic tool flagged DTC B16E700. Connectors and sensor resistance were normal. Further inspection found the harness where it routes from the left C-pillar trim to the rear floor had been bent repeatedly by long-term boot opening and closing, partially breaking the internal copper strands and causing an intermittent open circuit. The fix: cut out the damaged section, spliced in same-spec wire (0.5mm² shielded twisted pair), soldered the joints, sealed with heat shrink tubing, and rerouted the harness away from sharp sheet metal edges. No faults returned during one week of post-repair monitoring.
BYD DTC AI Analysis

Internally damaged sensor body replacement case

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A 2019 BYD E2 lightly bumped into an obstacle while reversing. DTC B16E700 appeared right after. The sensor had no external damage, but its resistance was infinite — indicating the internal piezoelectric element cracked from the impact shock. The collision was very light, so the sensor likely had an inherent weakness or hidden prior damage. The technician replaced the sensor, cleared the fault codes, and ran the calibration procedure (activating the SRS ECU learning mode via the diagnostic tool) to set the correct collision threshold.
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.