AU
B169416

DTC B169416 indicates the airbag control unit (SRS ECU) detects an internal operating voltage below the calibrated threshold (typically below 9V), or a functional fault in the ECU internal power management module or voltage regulation circuit — Atto 8

Safety System

DTC B169416 indicates the airbag control unit (SRS ECU) detects an internal operating voltage below the calibrated threshold (typically below 9V), or a functional fault in the ECU internal power management module or voltage regulation circuit.

This hardware-level fault indicates the SRS ECU cannot maintain the stable operating voltage required for its internal microprocessor, acceleration sensor, and ignition circuit.

When triggered, the ECU enters fail-safe mode.

This condition can cause complete airbag system failure (airbags fail to deploy during a collision), prevent seat belt pretensioner activation, or generate a false alarm resulting in unintended airbag deployment.

This fault poses a severe safety risk and requires immediate repair.

The B169416 fault code on the Atto 8 indicates the airbag control unit (SRS ECU) has detected low internal voltage (below 9V) or a power management fault, preventing stable operation of critical safety systems. This medium-severity issue can cause airbag failure or unintended deployment. Common causes include a faulty ECU voltage regulator or battery/charging system problems. Immediate inspection at an authorised dealer is required. Typical repair cost data is available from 4 recorded cases.
4
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Damaged SRS ECU internal power management chip or voltage regulator circuit, preventing the ECU from converting battery voltage into a stable 5V/3.3V internal operating voltage.
  • 2Severely discharged vehicle battery, generator failure, or excessive voltage drop in the dedicated SRS power supply circuit causes the ECU input voltage to remain below 9V.
  • 3Terminal oxidation, back-out, or poor contact at the SRS ECU connector (usually located under the center console), causing abnormally high resistance in the power supply circuit.
  • 4Loose or corroded ECU ground wiring harness (ground point G301 or G302), causing reference ground potential drift and abnormal voltage detection.
  • 5After a vehicle collision, the internal crash sensor in the SRS ECU triggers fuse protection or a software lock (Crash Data Locked). Replace the module.
What To Do
  • 1
    Read the complete fault code stream using the BYD VDS2000 or Launch X431 diagnostic tool. Confirm B169416 is currently active. Check for accompanying fault codes such as B1694-00 (power supply voltage too low) or U0151 (lost communication with SRS). Record the voltage value in the freeze frame data.
  • 2
    Measure the battery static voltage (should be ≥12.4V) and the charging voltage after starting (should be 13.5-14.5V). Check if the SRS ECU fuse (F1/15, usually 10A or 15A) in the instrument panel fuse box is blown. Measure the voltage between pin 1 of the ECU connector (constant power) and body ground.
  • 3
    Disconnect the battery negative terminal and wait 3 minutes (for capacitor discharge). Remove the center console side trim panels and remove the SRS ECU module (part number usually starts with 5A or 6A). Inspect the 32-pin connector for water ingress, green oxidation on the pins, or backed-out terminals. Measure the resistance between the power supply pin and the ground pin (should be <1Ω).
  • 4
    If the circuit voltage is normal (12V±0.5V) and the ground is good, but the fault code will not clear, this indicates an internal ECU fault. Replace the SRS ECU assembly. (Note: Match the vehicle configuration code. Do not mix ECUs from different airbag configuration versions.)
  • 5
    After installing the new ECU, perform Online Programming, write the Vehicle Configuration parameters, and perform a Zero Point Calibration on the crash sensor. Clear the fault codes and run a System Check to confirm the airbag warning lamp is off and communication is normal.
Real-World Cases
BYD DTC AI Analysis

Qin Pro DM airbag warning light suddenly illuminated while driving

✓
Vehicle: 2019 Qin Pro DM, 32,000 km. Symptom: While driving, the airbag warning light on the dashboard suddenly illuminated and stayed on. No accident history. Diagnosis: Scanned with VDS and retrieved current fault code B169416. Freeze frame data showed ECU voltage at 8.2 V. Measured battery voltage (normal). Inspected the SRS ECU connector and found slight oxidation on pin 1 (power supply); contact resistance measured 3.2 Ω. Fix: Cleaned pin 1 with electronic contact cleaner, applied conductive grease, and re-tightened the connector. Cleared the fault code. Followed up for one month—no recurrence.
BYD DTC AI Analysis

BYD E2 new car SRS system no communication

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Vehicle: 2020 BYD E2 EV, new vehicle PDI inspection. Symptom: Airbag warning light stays on, scan tool cannot communicate with SRS ECU. Diagnosis: Checked OBD pins 6 and 14 (CAN lines) — normal. No voltage at SRS ECU connector. Found loose SRS fuse slot in dashboard fuse box. Voltage intermittent when wiggling the fuse. Repair: Replaced fuse box base and tightened fuse pins. Fault resolved. Issue due to supplier assembly process.
BYD DTC AI Analysis

Qin EV showing SRS ECU fault after accident repair

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Vehicle details: 2019 Qin EV. Front collision, replaced front bumper and left front crash sensor. Symptom: After repairs, started the vehicle. Airbag light stays on. Read DTCs B169416 and B165C (front crash sensor fault). Diagnosis: Checked new sensor wiring – OK. The SRS ECU had recorded crash data and triggered its lockout protection. Standard unlock methods failed. Repair: Replaced SRS ECU (part number 5A-3638010C), performed online programming and sensor matching. Fault resolved.
BYD DTC AI Analysis

E3 SRS system low voltage fault after long-term parking

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Vehicle: 2020 E3. Started after sitting for 2 months. Symptoms: Hard starting, airbag warning light on, logged DTC B169416. Diagnosis: Battery voltage was only 10.5V. After charging, voltage returned to normal but the fault code persisted. Further inspection revealed aged capacitors inside the ECU; these could not maintain stable operating voltage after the high current surge during cold starting. Resolution: Replaced the SRS ECU and the battery. Advised the customer to disconnect the battery negative terminal for extended parking.
Other Atto 8 Fault Codes
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.B1109DTC B1109 indicates an open circuit in the communication line between the air conditioning system PM2.5 air quality sensor (dust concentration sensor) and the air conditioning control unit (AC ECU), or an open circuit within the sensor internal circuitry. Typically located in the air conditioning intake duct, this sensor monitors real-time PM2.5 particle concentration inside and outside the vehicle. It provides data to the automatic air conditioning system for intelligent switching between fresh air and recirculation modes and for controlling the air purification device. During an open circuit fault, the AC ECU cannot receive the air quality signal, triggering the system fail-safe mode. Symptoms typically include failure of the automatic recirculation function, abnormal air purification indicator light operation, or abnormal air quality data displayed on the air conditioning panel. Severe cases may compromise the cabin environment control strategy, but do not directly affect vehicle driving safety.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.B110B07This fault code indicates abnormal operation of the internal air pump (sampling pump) in the PM2.5 air quality detection module. The PM2.5 detector uses the laser scattering principle to measure particulate concentration and requires a built-in air pump to draw ambient air into the detection chamber at a constant flow rate. The ECU sets this code when it detects an open or short in the air pump drive circuit, abnormal current (stall or free-running), or abnormal speed feedback. This fault causes the automatic air conditioning system to lose air quality sensing capability, preventing automatic switching between fresh air and recirculation modes. The instrument cluster air quality display may show '--' or a fixed value, but the fault does not affect the vehicle powertrain or basic air conditioning cooling and heating functions.B173CDTC B173C indicates the Supplemental Restraint System (SRS) detects the Right Second Row Side Airbag squib circuit resistance exceeds the calibrated threshold (typically >4.5Ω). This fault is an active diagnostic result of the SRS system, indicating a high-resistance condition in the circuit between the Airbag Control Unit (ACU) and the airbag module. Causes for excessive resistance include increased contact resistance, a partially broken wiring harness, terminal oxidation, or an aging squib wire inside the airbag module. This fault causes the system to mark the airbag circuit as 'unreliable', meaning the airbag may fail to deploy during a collision. The fault typically illuminates the instrument cluster airbag warning light (SRS light) continuously, and some models also sound a warning buzzer.
Common problems reported for Atto 8 →Atto 8 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.