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B16C5

DTC B16C5 indicates an internal fault or critical function failure in the airbag control unit (SRS ECU) — Atto 3

Safety System

DTC B16C5 indicates an internal fault or critical function failure in the airbag control unit (SRS ECU).

The SRS ECU is the core controller of the safety system.

It monitors vehicle collision acceleration, processes crash signals, and controls the ignition triggering of protective devices such as airbags and seat belt pretensioners.

The following conditions trigger this DTC: ECU internal main control chip (MCU) self-test failure, abnormal internal acceleration sensor signal, ignition circuit driver fault, EEPROM read/write error, or persistent ECU power supply voltage or communication bus abnormalities.

When this fault occurs, the SRS system may enter fail-safe mode, preventing normal airbag deployment during a collision or, in extreme cases, causing unintended deployment.

This critical fault directly compromises occupant safety.

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Cases Logged
Real-World Cases
BYD DTC AI Analysis

B16C5-00 cannot be cleared after collision on Tang DM

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2021 Tang DM. After a minor front-end collision and front bumper replacement, the instrument cluster kept displaying the airbag warning light. Scan tool retrieved active DTC B16C5-00, accompanied by B1650-00 (driver airbag module). Inspection found no external damage to the SRS ECU, but it had internally logged the collision and locked. Online reset attempt failed. Replaced the SRS ECU (part number SC-3636900-B1), programmed the vehicle configuration, then completed ‘Restraint System Configuration’ and ‘Longitudinal Acceleration Sensor Calibration’. Fault resolved.
BYD DTC AI Analysis

Wading through water caused ECU internal short circuit in BYD Yuan EV

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2019 Yuan EV535. After heavy rain, drove through standing water. The next day the airbag warning light came on. DTC B16C5-00 stored. Removed and inspected the SRS ECU under the floor — the housing seal had aged, letting water in, and the circuit board had green copper corrosion. Measured a B+ short to ground. Replaced the ECU, cleaned up water on the wiring harness, and unclogged the sunroof drains (blockage let water into the A-pillar). Fault fully resolved.
BYD DTC AI Analysis

BYD Song Max intermittent B16C5 with CAN communication fault

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2019 Song MAX. Airbag warning light intermittently illuminated when driving on rough roads. Scan tool showed intermittent B16C5 and U0155-00 (lost communication with SRS). Inspection found pin 10 (CAN-H) of the 32-pin SRS ECU connector beneath the centre console had backed out, causing poor contact. Repaired the pin and applied conductive grease. Secured the wiring harness to prevent strain. Fault has not recurred.
BYD DTC AI Analysis

Aftermarket modifications caused abnormal power supply voltage in Qin Pro

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2020 Qin Pro petrol. Owner fitted a dashcam by tapping power from the airbag fuse, causing SRS ECU supply voltage fluctuations (minimum measured 8.2 V). Diagnosed DTC B16C5-00 and multiple voltage-related history codes. Restored the factory fuse circuit and ran a dedicated power feed for the aftermarket device. Cleared fault codes; system operation returned to normal. Warning: Never tap power from SRS system fuses (typically SB03, SB07).
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.