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B16F511

DTC B16F511 indicates an abnormally low-resistance connection between the first signal line (low-side reference line/signal return) of an SRS crash sensor (typically a front or side crash sensor) and body ground — Seal U

Safety System

DTC B16F511 indicates an abnormally low-resistance connection between the first signal line (low-side reference line/signal return) of an SRS crash sensor (typically a front or side crash sensor) and body ground.

This short to ground causes the SRS control unit (ACU) to detect an abnormal voltage near 0V, preventing it from correctly receiving the sensor acceleration signal.

The system enters fail-safe mode and disables the corresponding airbag deployment function.

In extreme cases, misinterpreting the crash signal may trigger unintended airbag deployment.

This critical circuit fault in the active safety system directly affects the normal protective function of the occupant restraint system.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Moisture ingress, burn damage, or mechanical damage to the crash sensor internal circuit board causes the signal terminal to short to the sensor housing (ground).
  • 2Sensor wiring harness chafes at a body panel hole, wiring harness bracket, or firewall pass-through, causing insulation damage that allows the wire to contact the chassis ground directly.
  • 3Improperly secured wiring harness or missing retaining clips after accident repairs allow the harness to rub against sharp metal edges over time, causing a progressive short circuit.
  • 4Fault in the SRS control unit (ACU) internal input-stage signal processing circuit, causing false detection of a sensor circuit short to ground.
  • 5Water ingress into the sensor connector (driving through water, high-pressure washing, seal aging) creates a conductive path between terminals, causing a short to ground.
What To Do
  • 1
    Use the BYD dedicated diagnostic tool (VDS2000/VDS2100) to read all fault codes. Check if DTC B16F811 (Line 2 short to ground) or other SRS-related fault codes are present, and record the crash trigger record in the freeze frame data.
  • 2
    Turn off the ignition, disconnect the negative battery terminal, and wait at least 3 minutes for the system to discharge. Based on the fault code location, remove the corresponding front collision sensor (B16 series) or side collision sensor (B17 series).
  • 3
    Use a multimeter to measure the resistance between sensor connector terminal 1 (first wire) and body ground. Normal resistance is greater than 10 kΩ (open circuit). A reading less than 1 Ω confirms a short to ground.
  • 4
    Disconnect the SRS control unit connector. Measure continuity between terminal 1 of the harness-side sensor connector and the corresponding terminal of the ACU connector. Measure the insulation resistance of this circuit to body ground. Inspect the wiring harness along its route for damage, crushing, or chafing.
  • 5
    If the wiring harness insulation is normal, measure the resistance between terminal 1 and terminal 2 (or the housing) on the sensor. Normal resistance is 2-5kΩ. If the resistance is close to 0Ω, replace the sensor. If both the sensor and wiring harness are normal, replace the SRS control unit due to an internal fault.
  • 6
    After repairing or replacing the faulty component, reconnect all connectors and connect the battery. Use the diagnostic tool to clear the fault code and perform an SRS system self-check. Perform the sensor calibration procedure (if applicable). Confirm the fault code does not return and the airbag warning light turns off normally.
Real-World Cases
BYD DTC AI Analysis

BYD Qin Pro petrol: SRS warning after accident repair

✓
2021 BYD Qin Pro petrol. After repairing front-end collision damage, the airbag warning light stayed on. The scan tool retrieved DTCs B16F511 (sensor line 1 short to ground) and accompanying B16F811 (sensor line 2 short to ground). The owner had already replaced the driver and passenger airbags, repaired the airbag control module, and replaced the seatbelts, but the fault persisted. We inspected the wiring harness and found nothing abnormal. We traced the fault to a damaged input stage circuit inside the SRS control unit (ACU), which caused false short-to-ground reports on the sensor lines. Replacing the SRS control unit with a new one and completing the online configuration cleared the fault.
Original source ↗
BYD DTC AI Analysis

BYD E2 airbag warning light came on after driving through water.

✓
2019 BYD E2. Airbag warning light stayed on after driving through water during heavy rain. Diagnosis showed DTC B16F511 pointing to the right front impact sensor. Inspection found the sensor connector located beneath the right front wheel arch liner; the seal had aged, allowing water ingress when wading. Water scale and electrolyte deposits created a short between terminal 1 and body ground. Cleaned the connector interior with compressed air, applied dedicated conductive grease, replaced the waterproof seal, and re-secured the wiring harness. Fault cleared.
BYD DTC AI Analysis

Chafed front compartment wiring harness causing intermittent short circuit in Qin EV

✓
2019 BYD Qin EV. Airbag light comes on occasionally on rough roads, normal on smooth roads. Scan tool retrieved historical DTC B16F511. Found the front impact sensor harness missing a rubber grommet at the edge of a front longitudinal member hole. Prolonged vibration wore through the insulation, exposing the copper conductors and causing the wire to intermittently ground against the chassis. Rewrapped the harness, reinforced with high-temperature insulation tape, installed a dedicated rubber grommet, and adjusted the mounting position. Fault resolved.
BYD DTC AI Analysis

E3 side impact sensor internal short circuit

✓
2020 BYD E3, no accident history. Airbag warning light came on suddenly and could not be cleared. DTC B16F511 pointed to the left B-pillar side impact sensor. Disassembly revealed signs of water accumulation in the sensor mounting hole. The internal piezoelectric element had moisture ingress due to water seepage through the B-pillar trim, causing the signal wire to short to the housing. Replaced with a new side impact sensor, inspected the window seals for aging and applied fresh sealant, and cleared the blocked drain holes. System returned to normal.
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.