AU
B16E8-00

This DTC indicates a short to ground in the signal circuit of the Supplemental Restraint System (SRS) Middle Rear Impact Sensor — Seal U

Safety System

This DTC indicates a short to ground in the signal circuit of the Supplemental Restraint System (SRS) Middle Rear Impact Sensor.

The sensor mounts in the center of the rear bumper or rear longitudinal rail area.

Electrically, the insulation resistance between the sensor signal wire (typically a LIN communication or analog signal line) and body ground drops below the threshold (generally <1Ω).

This causes the SRS control unit (ACU) to continuously receive an abnormally low voltage signal.

This fault forces the SRS into fail-safe mode.

As a result, the system may fail to accurately detect rear impact acceleration, preventing the airbags, curtain airbags, or seat belt pretensioners from deploying in time during a rear-end collision.

Furthermore, the ACU may interpret the condition as a wiring fault and completely disable the rear impact monitoring function, illuminate the instrument panel SRS warning lamp, and downgrade the vehicle's passive safety system.

BYD Qin series models typically use a dual-axis accelerometer design for this sensor.

The ACU continuously registers a short to ground as 'abnormal circuit current' or 'signal voltage below lower limit'.

The B16E8-00 fault code on the Seal U indicates a short to ground in the SRS middle rear impact sensor signal circuit. This is a high-severity safety fault that can disable rear impact detection and affect airbag or seat belt pretensioner deployment. Common causes include damaged rear bumper wiring or water ingress in the sensor. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
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Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Damaged wiring harness sleeve in the rear bumper area allows the wire to contact the metal body directly, causing a short to ground (common after reversing collision repairs or underbody scraping).
  • 2Rear center crash sensor body seal failure allows water ingress or internal moisture, causing the signal terminal to short to the sensor housing (ground).
  • 3Loose sensor connector (usually located inside the rear bumper or near the spare wheel well), backed-out pins, or corrosion causing the signal pin to short to ground against the connector housing.
  • 4Long-term vibration and chafing wear through the wiring harness insulation where it passes through body sheet metal holes or fixing brackets, causing contact with sharp body metal edges.
  • 5SRS control unit (ACU) internal signal acquisition circuit fault, causing a false short-to-ground detection (rule out by substitution).
What To Do
  • 1
    Safety preparation: Disconnect the 12V battery negative terminal and wait at least 3 minutes (or the time specified in the repair manual) to fully discharge the SRS energy storage capacitor and prevent accidental airbag deployment.
  • 2
    Fault confirmation: Use VDS or a dedicated diagnostic tool to read the complete SRS fault codes, record freeze frame data, and confirm the fault is current (Present) rather than historical.
  • 3
    Sensor location: On BYD Qin models, the center rear crash sensor mounts to the inner center of the rear bumper reinforcement or below the spare tire well. Remove the rear bumper inner liner to access the sensor.
  • 4
    Visual inspection: Check the sensor connector for looseness, signs of water ingress, and oxidized or bent pins; check the wiring harness sleeve for wear at the retaining clips and body panel holes.
  • 5
    Electrical measurement: Disconnect the sensor connector. Use a multimeter to measure the resistance between the harness-side signal wire and ground (normal: ∞ or >10 kΩ). If continuity exists, trace the circuit backward. Measure the resistance between the sensor body signal terminal and the housing (normal: 2-3 kΩ; close to 0 Ω if short-circuited).
  • 6
    Wiring harness repair: If the wiring harness is damaged, repair the insulation layer using heat-shrink tubing or waterproof tape. Replace the wiring harness assembly if necessary. Maintain sufficient clearance (>20 mm) between the wiring harness and body metal parts.
  • 7
    Component Replacement: If the wiring harness is normal but the sensor has an internal short circuit, replace the center rear crash sensor (verify the part number for the specific vehicle model; for the Qin series, this is typically the crash sensor assembly).
  • 8
    System verification: Reconnect all connectors and the battery. Turn the ignition switch ON. Use the diagnostic tool to clear the fault code. Perform the SRS system self-check. Verify B16E8-00 does not return and the instrument cluster SRS warning lamp turns off.
Real-World Cases
BYD DTC AI Analysis

After water ingress, an internal short in the sensor caused the SRS light to stay on.

✓
A 2017 Qin EV300 illuminated the SRS warning light after driving through deep water in heavy rain. Stored fault code: B16E8-00 (middle rear impact sensor short to ground). No collision damage was found on the rear bumper, but water had entered the sensor connector upon removal. The sensor’s signal terminal to housing resistance measured 0.3 Ω, confirming an internal short from water ingress. Replaced the middle rear impact sensor and waterproofed the connector with conductive grease and a waterproof cover, clearing the fault. Cause: deteriorated sensor seal allowed water to seep in through the connector gap during wading.
BYD DTC AI Analysis

Wiring harness chafing after accident repair caused intermittent fault.

✓
A non-authorised workshop repaired this 2018 Qin EV450 following a minor rear-end collision. One month later, the SRS warning light began illuminating intermittently. Diagnosis revealed DTC B16E8-00 as an intermittent active fault. Inspection of the rear impact sensor wiring harness routing found that the previous repair had not secured the harness correctly. A metal edge at the spare wheel well mounting bracket had cut through the insulation, allowing the wire to intermittently contact the body ground when driving over bumps. Repaired the damaged harness section, re-routed the wiring to specification, and protected it with a rubber protective sleeve, which completely resolved the fault.
BYD DTC AI Analysis

Connector corrosion caused signal short to ground.

✓
After three years of use in a coastal area, a 2017 Qin 100 showed an SRS warning light, with DTC B16E8-00 stored. Inspection found severe oxidation on the pins of the rear impact sensor connector (located inside the rear bumper). Green copper corrosion formed a low-resistance path (measured 12Ω) between the signal pin and the connector housing (ground). Cleaned the connector pins and socket, applied electronic contact cleaner, and replaced terminals where necessary. After cleaning, resistance returned to normal (>2kΩ). Cleared the DTC and the system returned to normal. Advised the owner to periodically check the sealing condition of underbody wiring harness connectors.
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.