AU
B16DF

DTC B16DF indicates the SRS (Supplemental Restraint System) ECU detects a communication interruption or physical disconnection of the Left Rear Impact Sensor — Atto 3

Safety System

DTC B16DF indicates the SRS (Supplemental Restraint System) ECU detects a communication interruption or physical disconnection of the Left Rear Impact Sensor.

This sensor typically mounts in the vehicle's left rear quarter panel, C-pillar, or rear longitudinal beam area to monitor collision acceleration from the left rear.

The ECU sets this fault code if it fails to receive a valid signal (including the sensor ID code, acceleration data, or heartbeat signal) within the preset monitoring period, or if it detects circuit resistance outside the normal range (typically greater than 10 kΩ or less than 1 Ω).

This fault disables the left rear collision detection function.

During a side impact or rear-end collision, the SRS ECU may fail to accurately assess collision severity, compromising the deployment strategy of the side airbags, curtain airbags, or seat belt pretensioners and posing a severe safety risk.

4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Loose or disconnected wiring harness connector: After accident repairs, interior trim removal and installation, or wading, the sensor connector inside the left rear door sill trim panel (usually a 3-pin or 2-pin waterproof plug) fails to lock fully, causing poor contact or complete disconnection.
  • 2Sensor harness open circuit or short circuit: Long-term vibration wears through the harness insulation where it passes through body sheet metal holes, seat slide rails, or door sill trim; rodents gnaw through the wiring causing a break; or the harness shorts to the body.
  • 3Crash sensor internal fault: Damaged internal accelerometer element, capacitor leakage, or ASIC chip failure prevents the sensor from sending valid data frames to the SRS ECU.
  • 4SRS ECU interface fault: The corresponding sensor interface circuit inside the airbag control module (usually the PSI5 or DSI bus communication chip) is damaged and cannot interpret the sensor signal.
  • 5Sensor mounting bracket deformation: A minor rear impact deforms the sensor mounting base, causing poor grounding between the sensor and the vehicle body or physical damage to the connector.
What To Do
  • 1
    Safety preparation: Disconnect the low-voltage battery negative terminal and wait at least 90 seconds to fully discharge the SRS capacitor. Read and record all DTCs and freeze frame data. Confirm B16DF is a current fault, not a history fault.
  • 2
    Physical inspection: Remove the left rear sill trim, lower C-pillar trim, or left side of the rear bumper. Visually check that the crash sensor connector (part number usually starting with 69C) is fully inserted and listen for a locking 'click'. Inspect the connector terminals for backed-out pins, corrosion, or signs of water ingress (green oxidation).
  • 3
    Circuit measurement: Disconnect the sensor and SRS ECU connectors. Use a multimeter to measure harness continuity: the sensor power supply wire (usually 12V or 5V) to ground resistance must be greater than 1MΩ. Test the signal wire (PSI5 bus) for shorts to ground and power. Measure the circuit resistance between the sensor and the ECU; resistance must be less than 1.5Ω.
  • 4
    Sensor test: Use an oscilloscope to measure the sensor signal wire waveform. A normal waveform shows a PSI5 protocol digital signal (current modulation, approximately 10-40mA amplitude). If the power supply is normal but the sensor outputs no signal, replace the left rear crash sensor (Note: pair or auto-configure the new sensor with the ECU).
  • 5
    System reset and verification: Reconnect all connectors, reconnect the battery, and clear the fault code using the diagnostic tool. Check the sensor live data stream to confirm the left rear crash sensor status shows 'Normal' and the acceleration value changes accordingly when lightly tapping the vehicle body. Perform the SRS system self-check and confirm B16DF does not return.
Real-World Cases
BYD DTC AI Analysis

Loose connector after accident repairs caused B16DF

✓
Following left rear door accident repairs, a 2021 BYD Tang DM displayed a constant airbag warning light on the instrument cluster. Retrieved DTC B16DF (current). Inspection revealed that after the left rear C-pillar trim panel was removed and refitted, the impact sensor's grey connector was not fully seated and the locking tab was not engaged. Reseated the connector, confirmed the lock was engaged, then cleared the DTC. The warning light extinguished and live data showed normal sensor communication.
BYD DTC AI Analysis

Wiring harness wear causing intermittent B16DF fault

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2019 BYD Song MAX: Airbag warning light intermittently illuminated when driving on rough roads. Scan tool showed DTC B16DF as an intermittent fault. Inspected the left rear sill wiring harness and found the insulation chafed through at the retaining clip, with copper strands partially fractured causing poor contact. Repaired the harness by cutting out the damaged section, soldering the wires and insulating with heat shrink tubing. Rerouted and secured the harness to prevent contact with bodywork. Fault resolved.
BYD DTC AI Analysis

Sensor Internal Fault Replacement Case

✓
2020 BYD Qin Pro EV logged B16DF DTC after extended parking. Checked connectors were secure, measured 12V sensor supply as normal, and found no shorts or opens in signal lines. Used oscilloscope and found no current modulation signal from the sensor. Replaced left rear collision sensor (part number: 69C-XXXXX), installing with the arrow pointing toward the front of the vehicle. Cleared the DTC and system returned to normal.
BYD DTC AI Analysis

Sensor connector corroded after wading

✓
After wading through water, the airbag warning light came on in a 2019 BYD Yuan EV. Diagnosis found DTC B16DF. Disassembly revealed water inside the left rear sill. The impact sensor connector terminals showed obvious electrochemical corrosion (green copper rust). Cleaned the ECU pins and wiring harness terminals (using electronic cleaner and fine sandpaper), replaced the waterproof seal, cleared the sill drain holes to ensure proper drainage, and resolved the fault.
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
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.