AU
B16E8

DTC B16E8 indicates the SRS (Supplemental Restraint System) control unit detects an abnormally low-resistance path (short to ground) between the Center Rear Impact Sensor (typically installed on the rear panel or C-pillar area) signal circuit and body ground — Seal U

Safety System

DTC B16E8 indicates the SRS (Supplemental Restraint System) control unit detects an abnormally low-resistance path (short to ground) between the Center Rear Impact Sensor (typically installed on the rear panel or C-pillar area) signal circuit and body ground.

This sensor uses a piezoelectric or capacitive accelerometer.

During normal operation, it outputs a 0.5-4.5V analog voltage signal to the SRS control unit to reflect collision acceleration.

A short to ground causes the control unit to continuously receive a voltage signal near 0V, triggering the following: 1) The system determines the sensor has failed, enters fail-safe mode, and disables the associated airbags (including side curtain airbags and rear collision protection functions); 2) During an actual rear collision, the system cannot accurately identify collision severity, causing delayed or no airbag deployment; 3) If the short-circuit resistance is unstable, it triggers an intermittent fault, causing the SRS warning lamp to illuminate erratically.

This is a hard fault.

Upon detection, the control unit stores the DTC and illuminates the instrument cluster airbag warning lamp.

The B16E8 fault code on the Seal U indicates a high-severity SRS airbag system fault, where the center rear impact sensor signal circuit is shorted to ground. This can disable related airbag functions and affect rear crash detection. Common causes include damaged rear wiring insulation or an internal sensor short. The vehicle should be inspected by an authorised dealer for wiring checks and sensor repair or replacement. Typical repair cost data is available.
4
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Rear wiring harness mechanical damage: Long-term vibration, friction from loaded cargo, or rear-end collisions wear the insulation where the rear wiring harness passes through the luggage compartment rear panel, C-pillar sheet metal holes, or retaining clips. The copper core directly contacts the vehicle body metal, creating a short to ground.
  • 2Internal sensor circuit fault: Collision sensor internal signal conditioning circuit failure or piezoelectric element package seal failure causes insulation breakdown between the signal output terminal and the sensor metal housing (ground), creating an internal short circuit.
  • 3Water ingress or seal failure: aging boot seal, poor rear windscreen sealing, or water entering the rear wiring harness connectors (usually located on both sides of the rear panel) during wading, causing electrolytic corrosion between terminals or a short to ground.
  • 4Improper accident repair: During rear collision repairs, incorrect wiring harness routing allows rear seat fixing bolts, interior trim panel clips, or metal edges to pinch the harness and damage the insulation.
  • 5Connector terminal corrosion: Long-term exposure to high-humidity environments (such as coastal areas or frequent vehicle washing) oxidizes the rear sensor connector (usually a 2-3 pin waterproof plug) terminals. The resulting green copper corrosion creates a short-to-ground path or an abnormal drop in resistance.
What To Do
  • 1
    Safety preparation: Set the vehicle to OFF, disconnect the 12V low-voltage battery negative terminal, and wait at least 3 minutes (or as required by the workshop manual, usually 5 minutes) to fully discharge the SRS backup power capacitor and prevent accidental airbag deployment during repair.
  • 2
    Fault Confirmation and Freeze Frame Analysis: Use VDS or a dedicated diagnostic tool to read the fault code status. Confirm B16E8 is a Current DTC, not a historical fault. Record the vehicle status from the freeze frame data (vehicle speed, timestamp, etc.) and analyze the environmental conditions when the fault occurred.
  • 3
    Sensor location and visual inspection: Refer to the vehicle repair manual to determine the exact location of the center rear impact sensor (Yuan/Song MAX models typically position it in the center of the rear panel; Tang series models position it at the lower section of the C-pillar). Remove the luggage compartment trim panel or C-pillar trim panel. Inspect the sensor exterior for physical damage, signs of water ingress, or corrosion.
  • 4
    Wiring harness integrity check: Visually inspect the sensor wiring harness routing (usually along the rear panel crossmember or up the C-pillar to the SRS ECU). Specifically check if the rubber grommet where the harness passes through the sheet metal hole is damaged, if the harness rubs against metal edges, or if the seat bracket or cargo has crushed or deformed the harness.
  • 5
    Electrical measurement and fault isolation: Disconnect the sensor connector. Use a multimeter to measure the resistance between the harness-side signal pin (usually SIG or ACC) and body ground. Normal resistance is infinity (OL). A reading of less than 5 Ω confirms a short to ground. Next, disconnect the SRS ECU connector. Measure the circuit in sections to determine whether the short is in the harness between the sensor and the ECU, or inside the sensor.
  • 6
    Repair or replace: If the wiring harness is shorted, repair the damaged wire (strip the insulation, solder the connection, and apply dual-wall heat-shrink tubing for waterproof insulation; replace the entire wiring harness section if necessary). If the sensor has an internal short circuit, replace it with an OEM collision sensor (Note: Some models require specific sensor orientation; during installation, point the arrow toward the front of the vehicle).
  • 7
    System verification and clearing: Reconnect all connectors and the battery. Use the diagnostic tool to clear the fault code. Perform the SRS system self-check cycle (usually requires turning the ignition switch to ON and waiting for the warning light to extinguish after the self-check). Confirm B16E8 does not recur.
  • 8
    Functional test and road test: Read the static crash sensor data stream and confirm the sensor output voltage is within the normal range (approx. 2.5V static value). Perform a road test to verify no intermittent faults occur when driving over uneven surfaces and the SRS warning light remains off.
Real-World Cases
BYD DTC AI Analysis

SRS light on after driving through water: Aged boot seal caused water ingress into sensor

✓
2019 BYD Yuan EV. The owner reported that after driving through floodwater during heavy rain, the airbag warning light stayed on. Scanned with VDS and retrieved current fault code B16E8. Inspected the rear area and found the centre rear impact sensor mounted centrally on the rear bulkhead, with obvious water stains and green copper corrosion inside its connector. Further inspection revealed that the boot seal had aged and deformed, allowing rainwater to enter the rear bulkhead cavity via the tail light housings. Rectification: replaced the centre rear impact sensor assembly, cleaned the connector terminals and applied conductive anti-corrosion paste, replaced the boot seal, and cleared the rear bulkhead drain holes. Followed up for three months after repair with no recurrence.
BYD DTC AI Analysis

False alarm after rear-end collision repair: Rear seat bolt crushed wiring harness

✓
A 2021 BYD Tang developed an intermittent SRS warning light after repairs at an independent shop following a low-speed rear-end collision. Diagnosis found an intermittent B16E8 DTC. Removing the rear interior trim revealed that the repair shop had not secured the rear bulkhead harness in its channel according to OEM routing. Instead, the rear seat mounting bolts had pinched the harness, damaging the insulation and exposing the copper conductors to the vehicle body. The technicians rerouted the harness, repaired the damaged wires (soldered and applied double-layer heat shrink tubing), and adjusted the seat mounting bracket to prevent interference. After clearing the DTCs, they road tested the vehicle repeatedly and confirmed the fault was gone.
BYD DTC AI Analysis

New vehicle assembly defect: damaged wiring harness protective sleeve causing a short to ground

✓
One week after delivery, the airbag warning light came on in a brand-new 2020 BYD Qin petrol model. Scanning retrieved fault code B16E8-00 (current). Inspection found the rubber grommet on the middle/rear impact sensor wiring harness was not fully seated where it passes through the C-pillar sheet metal hole, leaving the harness in direct contact with the sharp metal edge. Driving vibrations cut through the insulation, causing a short to ground. Repair action: Repair the damaged wire, replace the harness rubber grommet, fit a protective rubber ring over the sheet metal hole edge, and ensure a safe clearance between the harness and metal edge. This is an assembly process issue—vehicles from the same production batch require inspection.
BYD DTC AI Analysis

Sensor internal component aging: seal failure from high-temperature environment

✓
A 2019 BYD Song MAX, four years old, driven in a hot climate its whole life, came in with the SRS warning light stuck on. The scan tool pulled DTC B16E8. We measured the sensor harness ground resistance: normal, open circuit. After reconnecting the sensor, the signal wire to ground showed only 12Ω—a clear internal short. Opening the sensor revealed the PCB potting compound had aged and cracked, allowing a capacitor lead to touch the metal housing. Repair: replaced the center rear impact sensor assembly (confirmed correct part number for the vehicle), cleared the fault codes, and ran a system calibration. Some variants also require a zero-point calibration with the diagnostic tool.
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.