AU
B169517

DTC B169517 indicates the airbag control unit (SRS ECU/ACU) detected an anomaly during internal self-check, usually pointing to a fault in the ECU internal processor, memory, or power management module — Seal U

Safety System

DTC B169517 indicates the airbag control unit (SRS ECU/ACU) detected an anomaly during internal self-check, usually pointing to a fault in the ECU internal processor, memory, or power management module.

In the BYD diagnostic protocol, sub-code '17' specifically indicates an internal ECU circuit fault or a logic error resulting from supply voltage exceeding the threshold.

When the SRS ECU detects an internal oscillator fault, EEPROM data checksum failure, ADC conversion error, or watchdog reset, it sets this code and enters degraded mode.

This mode may disable some or all airbag deployment functions.

Because the ECU is the core of the passive safety system, this fault presents a severe safety risk and can prevent normal airbag deployment during a collision.

The B169517 fault code on the Seal U indicates the airbag control unit (SRS ECU) has detected an internal circuit fault or logic error, often triggered by abnormal supply voltage or hardware damage within the unit. Severity is medium, but safety risk is significant as airbag deployment may be degraded or disabled. Common causes include power supply fluctuations or aging internal components. Visiting an authorised dealer is recommended. Typical repair cost data is available based on 4 recorded cases.
4
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Abnormal battery voltage or power supply fluctuation: Prolonged battery depletion, battery aging, or a charging system fault causes the SRS ECU supply voltage to drop below 9V or exceed 16V, triggering ECU undervoltage/overvoltage protection and logging an internal fault.
  • 2SRS ECU internal hardware damage: Aging internal capacitors in the control unit, PCB corrosion (common in vehicles with water ingress), or physical damage to the processor chip causing self-check program failure.
  • 3Poor wiring harness connector contact: Oxidized or loose power, ground, or CAN bus pins on the ECU connector (usually located under the center console or behind the armrest box) cause intermittent communication loss or unstable power supply.
  • 4Software/calibration data corrupted: Abnormal internal ECU Flash data (e.g., data errors caused by an interrupted update or electromagnetic interference). Reflash or replace the ECU.
  • 5Electromagnetic interference or electrostatic damage: Improper electrical repairs (such as connecting or disconnecting the ECU connector while live, or using non-professional diagnostic equipment) damage the internal ECU circuitry.
What To Do
  • 1
    Initial inspection: Use VDS or a dedicated diagnostic tool to read all fault codes and freeze frame data. Confirm whether B169517 is a Current or History fault. Check the battery voltage (standard: above 12.6V; engine running: 13.8-14.5V) to rule out power supply system issues.
  • 2
    Visual and connection inspection: Disconnect the battery negative terminal, wait 3 minutes, then inspect the SRS ECU exterior (usually located below the gear selector or inside the center tunnel) for physical damage, water ingress, or a burnt odor. Inspect connector CA1 (or the corresponding model-specific connector) for looseness, and check the pins for oxidation or push-back. Measure the resistance at ground point G101 (or the corresponding ground point); the resistance must be less than 1 Ω.
  • 3
    Power and communication check: Reconnect the battery, turn the ignition switch to ON, and use a multimeter to measure the power supply voltage at the ECU connector. Constant power (B+) should be 12V and ignition power (IG) should be 12V. Measure the CAN-H and CAN-L voltage to ground (normally approx. 2.5V) and terminal resistance (approx. 60Ω) to rule out ECU abnormalities caused by network communication faults.
  • 4
    DTC verification: Clear the DTC, perform a road test or simulated bump test, and check if the fault recurs. If the fault is intermittent, inspect the wiring harness for loose connections. If the fault persists, proceed to the next step.
  • 5
    Software update: Use the latest VDS version to check for SRS system software updates. If available, update the ECU software following the standard procedure (Note: During the update, connect an external regulated power supply and maintain the voltage above 13.5V to prevent power loss from bricking the ECU).
  • 6
    Replacement and calibration: If the fault remains after reflashing, replace the SRS ECU assembly (the part number must match the vehicle configuration). Perform the following after replacement: ① Calibrate the crash sensor (level the vehicle using a spirit level); ② Write the VIN; ③ Set configuration parameters (e.g., vehicle model code, airbag configuration, seat belt type); ④ Cycle the ignition switch, verify no fault codes exist, and confirm the SRS warning lamp is off.
Real-World Cases
BYD DTC AI Analysis

Low battery on Qin Pro DM caused SRS ECU low voltage fault.

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Vehicle: 2019 BYD Qin Pro DM. Symptom: SRS warning light continuously illuminated on the instrument cluster. Scan tool retrieved active DTC B169517. Repair procedure: The vehicle had been stationary for an extended period, causing the battery voltage to drop to 10.8 V. The owner jump-started the vehicle, after which the fault appeared. SRS ECU supply voltage dropped to 8.5 V during cranking. Installed a new battery and cleared the fault codes. The fault did not return. Analysis: Low voltage caused abnormal operation of the internal reset circuit within the ECU, triggering a self-test fault. Recommendation: For vehicles left stationary for extended periods, disconnect the negative battery terminal or charge regularly to prevent low voltage from causing the ECU to store fault codes.
BYD DTC AI Analysis

BYD E2 SRS ECU internal short circuit after water ingress

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Model: 2020 E2 EV. Symptoms: After heavy rain, water leaked into the cabin carpet, the SRS warning light illuminated, and DTC B169517 stored, which could not be cleared. Repair: Removed the centre console and found obvious water stains on the SRS ECU housing. Connector CA1 had green corrosion inside. Disassembled the ECU and found PCB corrosion and shorted main chip pins. Replaced the SRS ECU assembly and treated the harness connector: cleaned it with precision instrument cleaner and sprayed it with contact protector. Also cleared the blocked air conditioning drain tube (the cause of the leak). Performed sensor calibration after replacement. Fault resolved.
BYD DTC AI Analysis

Loose SRS ECU connector causes intermittent fault on Qin EV

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Vehicle: 2019 Qin EV. Symptoms: SRS warning light occasionally illuminated while driving, extinguishing after turning the vehicle off and back on. The diagnostic scanner showed stored fault code B169517. Repair process: Inspection found the fault mostly occurred on rough roads. Removed the centre console and inspected SRS ECU connector CA1, finding the connector lock loose and pin 5 (power) slightly backed out. Resolution: Repaired the pin, secured the connector using a special retaining clip, and wrapped waterproof tape around the connector to prevent it from loosening. Cleared the fault codes and test-drove the vehicle for 50 kilometres; the fault did not recur.
BYD DTC AI Analysis

E3 software calibration error caused internal ECU fault code

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Model: 2020 E3. Symptoms: Following accident repairs (replacement of the front bumper and wiring harness), the SRS warning light remained illuminated, and DTC B169517 was stored. Repair: Checked the wiring harness connections and power supply voltage — both were normal. Identified that the replacement bumper harness was a non-genuine part, causing abnormal impedance in the left front crash sensor and indirectly triggering internal ECU communication errors. Replaced the crash sensor wiring harness with a genuine part, then used VDS2000 to refresh the software and rewrite the configuration on the SRS ECU (specifically the sensor configuration parameters). After the refresh, cleared the fault code and the system returned to normal.
Other Seal U Fault Codes
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.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.B110BDTC B110B indicates a fault in the internal air pump (sampling pump) of the PM2.5 air quality detector. This pump draws cabin or outside air into the PM2.5 sensor detection chamber, enabling the laser scattering sensor to measure real-time particulate matter concentration. The air conditioning controller (or BCM) sets this DTC upon detecting an open or short circuit in the pump drive circuit, or abnormal current caused by a seized pump motor. This fault disables the "Green Clean" system, causes the instrument cluster air quality display to read abnormally or disappear, and disables the automatic fresh air/recirculation switching function. It does not affect the vehicle powertrain or core thermal management functions.B173712DTC B173712 indicates a short to power in the firing circuit of the right second-row side airbag module in the Supplemental Restraint System (SRS). Specifically, the "right second-row side airbag" typically refers to the side impact airbag located in the right B-pillar or the side of the right seat. The "12" suffix indicates a circuit short to battery positive (B+). This fault causes the following conditions: 1) The airbag may fail to ignite and deploy during a collision, resulting in a loss of side impact protection. 2) In extreme cases, unintended triggering may cause accidental airbag deployment. 3) The SRS control unit detects abnormally high circuit voltage (typically above 4.5V) and enters fault protection mode. This may disable the entire airbag system and continuously illuminate the instrument cluster airbag warning light.
Common problems reported for Seal U →Seal U 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.