AU
B169A-00

B169A-00 indicates an internal fault in the airbag control unit (SRS ECU) or a system-level communication fault — Seal U

Safety System

B169A-00 indicates an internal fault in the airbag control unit (SRS ECU) or a system-level communication fault.

The SRS ECU is the core control module of the vehicle’s passive safety system, responsible for monitoring crash sensors, controlling airbag deployment, triggering seat belt pretensioners, and recording crash data.

This fault code indicates the ECU self-check detected an internal processor fault, memory checksum failure, internal bus communication interruption, or critical circuit abnormality.

This fault constitutes a serious safety hazard; it may prevent the airbag system from deploying correctly during a collision or cause unintended deployment.

In BYD Qin series vehicles, the SRS ECU typically mounts beneath the center console or in the central armrest area, communicating with the vehicle network via the CAN bus.

The B169A-00 fault code on the Seal U indicates an internal fault in the airbag control unit (SRS ECU) or communication failure, posing a medium safety risk. Common causes include internal hardware damage or power supply issues like low battery voltage or blown fuses. As five real cases have been recorded, typical repair cost data is available. You should visit an authorised dealer immediately for diagnosis and repair.
5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1SRS ECU internal hardware fault: damaged microprocessor, EEPROM memory chip, or internal power supply circuit causing self-test failure
  • 2Power supply system fault: Battery voltage too low (below 9V) or too high (above 16V), SRS dedicated fuse (ECU-B, AIR BAG) blown, ground terminal loose or oxidized.
  • 3CAN bus communication fault: A short or open circuit in the CAN-H and CAN-L lines, or an abnormal terminating resistor, interrupts communication between the ECU and the vehicle network.
  • 4External physical damage: Vehicle wading, water ingress or moisture at the ECU mounting location causing circuit board corrosion, or damage to the internal ECU acceleration sensor following a vehicle accident.
  • 5Peripheral component short circuit: Internal short circuit in the clock spring (spiral cable), crash sensor, or seat occupancy recognition sensor triggers an ECU protective fault.
What To Do
  • 1
    Use a dedicated BYD diagnostic tool (VDS or ED400) to read all fault codes. Check for accompanying U-prefix communication fault codes (such as U0151, U0164) and history freeze frame data.
  • 2
    Check the vehicle battery voltage (static voltage ≥12.4V; 13.5-14.5V after startup). Check if the SRS system fuse in the instrument panel fuse box (usually labeled SRS, AIR BAG, or ECU-B) is blown.
  • 3
    Locate the SRS ECU (on Qin series, this is typically in the lower center console; remove the center console trim). Inspect the connector for looseness and check the pins for oxidation or water ingress. Measure the ground point resistance (should be <1Ω).
  • 4
    Measure the SRS ECU power supply terminals (constant power B+, ignition power IG) and CAN bus voltage (CAN-H approximately 2.6-2.8V, CAN-L approximately 2.2-2.4V, resistance approximately 60Ω).
  • 5
    Disconnect the negative battery terminal, wait 3 minutes, and attempt to clear the fault code. Power on the vehicle again to perform an SRS system self-check. If the fault code fails to clear or reappears immediately, replace the SRS ECU control unit.
  • 6
    After replacing the ECU, perform online programming (Coding), write the vehicle model configuration, and calibrate the system. Use the diagnostic tool to perform the 'Crash Output Test' to verify normal system function.
Real-World Cases
BYD DTC AI Analysis

Qin EV450 SRS ECU internal processor fault

✓
The airbag warning light stayed on constantly during normal driving, with no accident history. Used VDS to read fault code B169A-00, with no accompanying communication fault codes. Checked the ECU connector and found no loose connections; supply voltage at 12.6V was normal, and CAN bus waveform was normal. Diagnosed as an intermittent internal microprocessor fault in the ECU. Replaced the SRS ECU and programmed it. Fault cleared and the airbag warning light went out after self-check.
BYD DTC AI Analysis

Qin 100: Low auxiliary battery voltage caused system low voltage fault

✓
After extended parking, the battery drained and the vehicle would not start. Following a jump-start, the airbag warning light came on and stayed on. The diagnostic tool read codes B169A-00 and B1620-00 (backup power supply fault). Inspection found the original battery had only 28% life remaining; voltage instability caused the ECU self-check to fail. Replaced the battery, cleared the fault codes, and performed three ignition cycle self-checks. The SRS system returned to normal and the fault has not reappeared.
BYD DTC AI Analysis

BYD Qin EV300 ECU corrosion fault after water ingress

✓
After driving through standing water, the airbag warning light illuminated. Fault code B169A-00 retrieved. Disassembly revealed the SRS ECU installed under the central tunnel. Blocked drain holes caused water to accumulate and submerge the unit, leaving clear corrosion on the circuit board. Replaced the SRS ECU, drained the water from the central tunnel, cleared the drain holes, and treated oxidation on the wiring harness connectors to resolve the fault. Recommend checking under the carpet for other modules that may also be at risk of water ingress.
BYD DTC AI Analysis

Aftermarket modification caused CAN bus interference fault

✓
After the owner installed an aftermarket large-screen navigation system, the airbag warning light stayed on constantly with DTCs B169A-00 and U0151 (lost communication with SRS) stored. Inspection found the installer had mistakenly connected the SRS CAN lines in parallel with the entertainment system CAN lines while splicing into the CAN wiring, causing abnormal bus loading. After restoring the original wiring harness connections and fitting an isolation gateway, SRS communication returned to normal, and the fault did not recur after clearing the codes.
BYD DTC AI Analysis

Clock spring short circuit triggered ECU protective fault

✓
The airbag warning light illuminated after abnormal steering wheel movement, with DTC B169A-00. Inspection found the clock spring (spiral cable) beneath the steering wheel had developed an internal short from prolonged wear, with resistance measuring 0.3 Ω (normal range: 2–5 Ω). The short-circuit current triggered the SRS ECU protection mode. Replaced the clock spring, inspected the airbag harness (no damage), cleared the fault codes, and the system returned to normal.
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.