AU
B169E-00

DTC B169E-00 indicates the airbag electronic control unit (SRS ECU/ACU) detected a fault during its internal self-check — Qin Plus

Safety System

DTC B169E-00 indicates the airbag electronic control unit (SRS ECU/ACU) detected a fault during its internal self-check.

Specifically, this constitutes a hardware or logic fault in the ACU internal processor, memory (EEPROM/Flash), power management module, or internal communication bus, rather than a problem with external sensors, wiring harnesses, or crash detection circuits.

This fault indicates the ACU cannot guarantee reliable execution of the airbag deployment logic during a collision, making it a safety-critical fault.

In BYD Qin series vehicles, the ACU typically mounts in the center tunnel or beneath the dashboard and manages multiple deployment circuits, including the front airbags, side curtain airbags, and seat belt pretensioners.

The B169E-00 fault code on the Qin Plus indicates an internal hardware or logic fault within the airbag control unit (ACU), affecting its processor, memory, or power management systems. This medium severity issue means the airbag system may not deploy reliably in a crash. Common causes include internal power regulator failure or memory corruption. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available based on 5 recorded cases.
5
Cases Logged
5
Causes
Likely Causes — Qin Plus
  • 1ACU internal power management IC fault: A damaged internal voltage regulator chip causes abnormal power supply to the 3.3V or 5V logic circuit, triggering an internal watchdog reset failure.
  • 2EEPROM data corruption: Electromagnetic interference, voltage transients, or aging causes CRC check errors in memory configuration data, crash records, or calibration parameters.
  • 3Main control MCU crash or program runaway: ARM core processor enters an unrecoverable state due to abnormal clock signal, PCB cold solder joints, or software bug.
  • 4CAN transceiver physical layer fault: Damaged internal ACU CAN_H/CAN_L drive circuit interrupts vehicle network communication or causes error frame accumulation.
  • 5BGA solder joint cracking due to thermal cycling: Prolonged high-temperature sun exposure (e.g., the installation position under the dashboard in the Qin series) creates micro-cracks in the main chip solder balls, causing intermittent poor contact.
What To Do
  • 1
    Use a dedicated diagnostic tool (such as BYD VDS or Launch X431) to read all fault codes, check for B169E-00 and accompanying U-series communication fault codes, and record freeze frame data.
  • 2
    Perform an ACU power supply integrity check: measure constant power (B+, should be 12V±0.5V), ignition power (IGN, should be 12V with key ON), and ground (GND, resistance <1Ω) to rule out external power supply faults.
  • 3
    Check the CAN bus physical layer: Measure the resistance between OBD port pin 6 (CAN-H) and pin 14 (CAN-L) (approximately 60 Ω; the Qin series typically uses dual terminating resistors), and check the waveform for interference.
  • 4
    Attempt software recovery: If the vehicle supports online flashing, upgrade or reflash the ACU control unit software (back up the original coding data) and check if the fault code clears.
  • 5
    Power reset procedure: Disconnect the 12V battery negative terminal for at least 5 minutes. Unplug the ACU connector (usually located at the front of the center tunnel or behind the glovebox). Check the pins for oxidation, then reconnect and test.
  • 6
    Replace the ACU assembly: If the fault persists, replace the airbag control unit with one of the same part number (ACU part numbers for Qin EV300/450 and Qin DM/petrol versions may differ; check the configuration table).
  • 7
    Perform coding matching: Use the diagnostic tool to write the vehicle VIN and model configuration code (such as airbag quantity, seat belt type, and knee airbag presence), and set the collision threshold parameters.
  • 8
    Comprehensive system self-check: Perform 'Airbag System Configuration', 'Crash Sensor Calibration', and 'All Ignition Circuit Resistance Test'. Verify the system generates no new fault codes and the instrument cluster airbag warning lamp turns off after the self-check.
Real-World Cases
BYD DTC AI Analysis

Qin EV300 ACU internal memory verification failed

✓
A 2017 Qin EV300 with 60,000 km had the airbag warning light constantly on. VDS read DTC B169E-00. Power supply, ground and CAN lines were normal. Offline ACU software refresh failed with 'Internal Memory Check Error'. Replaced the ACU (part number BC-5820100), performed 'ECU Coding' to write the vehicle configuration (Qin EV300 with side curtain airbags), and performed 'Crash Sensor Initialization'. Fault resolved. Analysis of the returned old part confirmed an internal EEPROM page write error.
BYD DTC AI Analysis

Jump-starting the Qin 100 caused ACU overvoltage damage

✓
2017 BYD Qin 100 had a flat battery. The owner performed an incorrect jump start using a 24V truck battery, causing the airbag warning light to illuminate. Diagnosis revealed DTC B169E-00 accompanied by multiple U-class communication faults. Measuring the ACU power input showed the internal protection diode had broken down; the ACU sustained physical damage. After replacing the ACU, inspection revealed that overvoltage had also damaged the front impact sensor (mounted on the front side member). Replaced both the front impact sensor and the ACU, performed 'System Configuration' and 'Sensor Learning', and the system returned to normal.
BYD DTC AI Analysis

Qin EV450 ACU software version defect

✓
The 2018 Qin EV450 started throwing DTC B169E-00 occasionally after a BMS software upgrade. The vehicle had no collision history. The shop found the ACU software was an early version (V1.02) with a bug causing CAN communication conflicts under certain conditions. They confirmed the issue via a BYD technical service bulletin and upgraded the ACU software to V1.05. After clearing the fault codes and doing several test drives, the fault did not recur. This is a software fault—no hardware replacement needed.
BYD DTC AI Analysis

High temperatures caused cold solder joints in the ACU on the BYD Qin 80.

✓
In Hainan, a 2017 BYD Qin 80 experienced intermittent airbag warning light illumination during summer. DTC B169E-00 was stored as a history code. The fault did not occur when cold but reappeared when hot (after sun exposure). Disassembled the ACU and found cold solder joints on the BGA connections of the main control chip (Freescale series). To repair, reball and resolder the BGA connections using a BGA rework station, or replace the ACU. Also check whether the thermal insulation under the dashboard has detached to improve the ACU's cooling environment.
BYD DTC AI Analysis

Replaced ACU without coding; fault persisted.

✓
The workshop replaced the ACU on an accident-damaged Qin EV300, but DTC B169E-00 remained. They found the new ACU was blank — no vehicle configuration data had been written. Using VDS, they performed 'Airbag System Configuration', selected the correct model (2017 Qin EV300 with 6-airbag configuration), wrote the VIN, and carried out 'ECU Online Matching' (requires connection to BYD server for authorization). After completing, they ran 'System Self-Check' and the fault code cleared successfully.
Other Qin Plus 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.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.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.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.B173BDTC B173B indicates an abnormal electric A/C compressor speed feedback signal or a communication fault between the compressor controller and the motor. In BYD new energy models (e.g., Tang, Song, Qin, and Yuan series), this DTC belongs to the HVAC subsystem within the Body Control system and specifically involves the electric compressor closed-loop control circuit. The ECU sets this DTC when the compressor controller (IPM) fails to receive a valid pulse signal from the Hall speed sensor for more than 3 continuous seconds, or when the deviation between the detected actual speed and the target commanded speed exceeds the calibrated threshold (typically >500 rpm). This fault forces the A/C system into fail-safe mode and stops compressor operation. Symptoms include a complete lack of cooling, intermittent cooling, or a sharp decrease in cooling performance. The instrument cluster A/C warning lamp may also illuminate. Prolonged operation with this fault can degrade high-voltage system insulation or cause controller overcurrent damage.
Common problems reported for Qin Plus →Qin Plus 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.