AU
B16E700

DTC B16E700 indicates the airbag system (SRS) detects a communication interruption or physical disconnection of the Middle Rear Impact Sensor — Atto 8

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.

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Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Rear bumper wiring harness connector loose or disconnected: Driving on rough roads or through water can loosen the crash sensor plug inside the rear bumper due to vibration. Poor sealing can also cause pin corrosion and oxidation, resulting in poor contact.
  • 2Open circuit inside the sensor body: Physical impact (such as a minor rear-end or reversing collision) or long-term aging damages the center rear impact sensor's internal piezoelectric element or circuit board, causing an open circuit.
  • 3Harness breakage or wear: Repeated bending or friction against other components breaks the copper wires where the wiring harness from the main body harness to the rear bumper passes through the rear panel and floor trim strip, causing an open circuit fault.
  • 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 incorrectly detect a disconnected sensor.
  • 5SRS control unit connector issue: A loose control unit connector under the centre console or in the front compartment causes poor contact at specific pins (centre rear impact sensor signal wire).
What To Do
  • 1
    Fault confirmation and freeze frame analysis: Use VDS2000 or a dedicated BYD diagnostic tool to read fault codes. Confirm B16E700 is a current fault (Active). Record freeze frame data (ambient temperature and vehicle status). Check for other accompanying SRS-related fault codes (such as B16E800 short to ground).
  • 2
    Visual and connector inspection: Remove the rear bumper trim panel and locate the center rear impact sensor (usually located in the middle or left side of the rear crash beam). Verify the sensor connector is fully seated, confirm the connector waterproof sealing ring is intact, and inspect the pins for green oxidation, backed-out pins, or deformation.
  • 3
    Wiring continuity test: Disconnect the battery negative terminal. Disconnect the SRS ECU and sensor connectors. Use a multimeter to measure sensor harness continuity between the ECU and sensor ends. Resistance must be less than 1 Ω. Measure signal wire insulation to ground and power supply to confirm no short circuit.
  • 4
    Sensor body inspection: Use a multimeter to measure the sensor body resistance (normal value is typically 500Ω-10kΩ; refer to the repair manual for specifics). If the reading shows infinity (OL), the sensor has an internal open circuit. Lightly tap the sensor housing and observe if the resistance value fluctuates to confirm 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. The resistance must be less than 1Ω. If necessary, sand the surface and retighten the bolt.
  • 6
    Replacement Verification and System Reset: If confirming a faulty sensor, replace it with a genuine part (match the part number to the vehicle model, e.g., E2/Qin EV common part). Apply conductive grease during installation. Reconnect all connectors, restore the battery, use the diagnostic tool to clear the fault code, and execute the 'SRS system self-check' procedure. Verify B16E700 does not return and the airbag warning light turns off.
Real-World Cases
BYD DTC AI Analysis

Centre rear impact sensor communication fault after water wading

✓
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.

✓
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

✓
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

✓
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 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.