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B169E-00

DTC B169E-00 indicates the airbag electronic control unit (SRS ECU/ACU) detected a fault during its internal self-check — Atto 3

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.

5
Cases Logged
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 Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
Data confidence: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.