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 — Seal U

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.

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Cases Logged
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Causes
Likely Causes — Seal U
  • 1A damaged internal power management chip or voltage regulator circuit in the SRS ECU prevents conversion of battery voltage into a stable 5V/3.3V internal operating voltage.
  • 2Severe vehicle battery discharge, a generator fault, or excessive voltage drop in the dedicated SRS power supply circuit causes the ECU input voltage to remain continuously below 9V.
  • 3Terminal oxidation, back-out, or poor contact at the SRS ECU connector (usually located under the center console) causes an abnormal increase in power supply circuit resistance.
  • 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 SRS ECU internal crash sensor triggers fuse protection or software lock (Crash Data Locked). Replace the module.
What To Do
  • 1
    Use the BYD VDS2000 or Launch X431 diagnostic tool to read the complete fault code stream. Confirm B169416 is 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 from the freeze frame data.
  • 2
    Measure the battery static voltage (should be ≥12.4 V) and the charging voltage after start-up (should be 13.5–14.5 V). Check if the SRS ECU fuse (F1/15, usually 10 A or 15 A) in the instrument panel fuse box is blown. Measure the voltage between ECU connector pin 1 (constant power) and body ground.
  • 3
    Disconnect the 12V battery negative terminal and wait 3 minutes to discharge the capacitors. Remove the center console side trim panels, then remove the SRS ECU module (part number usually starts with 5A or 6A). Inspect the 32-pin connector for water ingress, green pin oxidation, or backed-out terminals. Measure the resistance between the power supply pin and the ground pin (should be <1Ω).
  • 4
    If circuit voltage is normal (12V±0.5V) and ground is good, but the fault code will not clear, this indicates an internal ECU fault. Install a new SRS ECU assembly. (Note: The ECU must 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, and perform crash sensor calibration (Zero Point Calibration). Clear the fault codes and perform a System Check to confirm the airbag warning light turns 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 Seal U 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.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.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.B110AThis DTC indicates interrupted CAN bus communication or abnormal data between the air conditioning control unit (ACU) and the PM2.5 air quality sensor. The PM2.5 sensor monitors particulate concentration inside and outside the vehicle and provides the basis for purification control in the automatic air conditioning system. The ACU triggers this fault if it fails to receive a valid CAN message from the sensor within the specified period (usually 100-500 ms), if message verification fails, or if the signal frame times out. Although this fault does not affect vehicle driving safety, it disables the automatic air purification function. The air conditioning system cannot automatically switch between recirculation and fresh air modes or activate the air purification mode based on air quality. A persistent fault may restrict the thermal management strategy.
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.