AU
B16E7

DTC B16E7 indicates the airbag control unit (SRS ECU) cannot establish normal communication with the Middle Rear Impact Sensor — Seal U

Safety System

DTC B16E7 indicates the airbag control unit (SRS ECU) cannot establish normal communication with the Middle Rear Impact Sensor.

This sensor typically mounts in the vehicle's central rear area (such as the rear panel, rear floor, or near the C-pillar) and monitors rear collision acceleration.

When the ECU detects an open sensor circuit, an internal sensor fault, or a communication interruption, it stores this fault code and illuminates the airbag warning light.

Consequently, during a rear-end collision, the airbag system may fail to correctly determine collision severity and deploy the rear airbags or seat belt pretensioners in time, severely compromising passive safety functions.

3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Loose, disconnected, or poor contact at the center rear crash sensor wiring harness connector, commonly resulting from vehicle wading, corrosion after water ingress, or failure to fully seat the connector after repairs.
  • 2Open or short circuit in the sensor power supply or signal circuit due to wiring harness aging, wear, crushing, or rodent gnawing.
  • 3Internal fault in the center rear crash sensor body, such as a damaged accelerometer element, internal circuit fault, or seal failure causing water ingress.
  • 4After a rear-end collision, sensor mounting bracket deformation disconnects the sensor and wiring harness connector, or the components failed to seat correctly during accident repairs.
  • 5Airbag Control Unit (SRS ECU) internal communication port fault or loss of software calibration data (less common but possible)
What To Do
  • 1
    Safety preparation: Disconnect the battery negative terminal and wait at least 90 seconds to fully discharge the SRS system capacitors and prevent accidental airbag deployment.
  • 2
    Fault confirmation: Use the BYD dedicated diagnostic tool (VDS2000/VDS2100) to read the fault code. Confirm B16E7 is a current fault (not a history fault) and record the freeze frame data.
  • 3
    Locate the sensor: Refer to the vehicle repair manual to locate the center rear crash sensor (usually in the center of the rear panel or under the rear seats). Visually inspect the sensor exterior for damage and the mounting bracket for deformation.
  • 4
    Connector inspection: Check that the sensor harness connector is fully seated and the locking tab is intact. Inspect the terminals for oxidation, backed-out pins, or corrosion. Clean or replace the connector if necessary.
  • 5
    Circuit measurement: Disconnect the SRS ECU and sensor connectors. Measure harness continuity (should be less than 1 Ω). Measure signal wire insulation resistance to ground and to power (should be greater than 10 MΩ). Check the reference voltage (normal: 9-13 V).
  • 6
    Sensor test: If the wiring is normal, replace the center rear crash sensor with a known good unit for a substitution test, or measure the sensor resistance (compare against the workshop manual standard value, typically 2-5kΩ).
  • 7
    System reset: After repair, reconnect all components and the battery. Use the diagnostic tool to clear fault codes. Perform the 'SRS system self-check' and 'crash sensor calibration' procedures. Confirm the warning light turns off and the system has no fault codes.
Real-World Cases
BYD DTC AI Analysis

BYD Qin rear collision sensor connector loose case

✓
Vehicle: BYD Qin 2020. Symptom: SRS warning light on instrument cluster. DTC B16E7-00 (middle rear collision sensor disconnected). Diagnosis: Inspected the middle rear collision sensor in the center of the trunk. Found the wiring harness connector not fully locked; the plug pulled out easily. Owner reported the vehicle had previous bodywork and painting at a repair shop—likely the connector was not reconnected properly. Checked wiring continuity with a multimeter, results normal. Sensor resistance 2.8 kΩ, within spec. Fix: Reconnected the sensor plug and locked the tab securely. Cleared fault codes; system returned to normal.
Original source ↗
BYD DTC AI Analysis

BYD Song MAX Rear Impact Sensor Wiring Harness Open Circuit Case

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Vehicle: BYD Song MAX 2019 Symptom: The SRS warning light illuminated suddenly after driving on rough roads. Diagnosis: Connected the scan tool and retrieved DTC B16E7. Inspected the center rear impact sensor and found the wiring harness chafed where it passes through the body sheet metal opening. The damaged insulation caused an intermittent open circuit in the signal wire. Measured the circuit and found the sensor power wire had unstable resistance when the wiring was moved. Repair: Cut out the damaged section of the wiring harness, soldered the connections and applied waterproof insulation. Rerouted the harness to avoid contact with sharp sheet metal edges, and fitted protective corrugated tubing. Fault resolved.
Original source ↗
BYD DTC AI Analysis

BYD Tang sensor failure following rear-end collision

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Vehicle: 2021 BYD Tang. Symptom: The SRS warning light remained illuminated after rear-end collision repairs, with DTC B16E7 displayed. Diagnosis: Inspected the rear panel area and found the centre rear impact sensor had sustained shock damage in the accident. The mounting bracket was slightly deformed; although the sensor appeared externally intact, the internal accelerometer had failed. Measured sensor output signal voltage at 0 V (reference: 2.5 V) and infinite resistance across the sensor. Repair: Replaced the centre rear impact sensor with a new unit and corrected the mounting bracket to the standard position—sensor mounting angle perpendicular to the vehicle horizontal plane. Performed sensor calibration using a dedicated diagnostic tool and cleared the fault code.
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.