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B169C

DTC B169C indicates the airbag control unit (SRS ECU) detects a critical internal function failure or self-diagnostic abnormality — Atto 3

Safety System

DTC B169C indicates the airbag control unit (SRS ECU) detects a critical internal function failure or self-diagnostic abnormality.

This typically involves an ECU internal processor (MCU) calculation error, a non-volatile memory (EEPROM/Flash) data verification failure, abnormal power management module (PMIC) output, or the safety monitoring circuit (Watchdog) triggering a reset.

As the core of the passive safety system, the SRS ECU receives crash sensor signals, determines collision severity, and triggers airbag deployment and seat belt pretensioners.

This fault means the ECU cannot guarantee a normal response during a collision, potentially causing the airbags to fail to deploy or deploy unintentionally.

This constitutes an Automotive Safety Integrity Level (ASIL) D functional safety fault.

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Cases Logged
Real-World Cases
BYD DTC AI Analysis

Loose power connection caused intermittent SRS ECU fault in Tang DM

✓
Symptoms: Instrument panel airbag warning light illuminated intermittently. Retrieved fault codes B169C (current) and B169C-00 (history). Diagnosis: Measured ECU supply voltage and found Terminal 30 fluctuating between 12.1V and 11.4V (should remain stable above 12.6V). Traced the fault to internal oxidation in the main wiring harness between the battery positive terminal and fuse box. Contact resistance measured 3.2Ω. Resolution: Replaced the battery positive cable assembly, cleaned and tightened all earth points. Fault resolved.
BYD DTC AI Analysis

Yuan EV CAN bus short circuit causes SRS communication fault

✓
Symptoms: Vehicle fails to engage high voltage; dashboard displays 'Please check SRS system'. DTCs B169C and U0151 present (loss of communication with SRS). Diagnosis: Measured OBD port CAN line resistance at 0Ω (short between CAN-H and CAN-L). Sectional inspection found the right A-pillar wiring harness had been crushed during carpet removal/installation, damaging the insulation and causing a short in the twisted pair. Resolution: Repaired the harness insulation, rerouted the harness to avoid the pedal mechanism, and confirmed normal CAN waveforms (rectangular waves without distortion).
BYD DTC AI Analysis

Collision sensor power supply fault triggered ECU protection — Song MAX

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Symptoms: After accident repair, the airbag warning light stays illuminated with fault codes B169C and B1620 (left front impact sensor fault). Diagnosis: Inspection found the left front impact sensor wiring harness damaged during the accident. The 5V supply wire shorted to ground, triggering the SRS ECU internal voltage regulator overload protection. Solution: Replaced the left front impact sensor and wiring harness. Performed 'Sensor ID Learning' and 'Configuration Reset' using a diagnostic tool. Cleared fault codes; system returned to normal.
BYD DTC AI Analysis

Software calibration error caused ECU self-test failure in Qin Pro

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Symptoms: After replacing the instrument panel assembly, the airbag warning light stays on with DTC B169C (configuration error). Diagnosis: The new instrument cluster communicates normally with the SRS ECU, but reading the ECU variable configuration found that 'seat occupancy recognition' was incorrectly coded as 'equipped' when the vehicle lacks this feature, causing the ECU safety algorithm self-check to fail. Solution: Used the VDS diagnostic scanner to modify the variant coding, changing the seat type to 'standard seat'. Performed an ECU reset and the fault code cleared.
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.