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 — Atto 8

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 Atto 8 indicates an internal fault within the airbag control unit (SRS ECU), typically caused by abnormal battery voltage or internal hardware damage such as aging capacitors or PCB corrosion. Rated as medium severity, this fault may disable some or all airbag deployment functions. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from 4 recorded cases.
4
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 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.
  • 2Internal SRS ECU hardware damage: Aging internal control unit capacitors, PCB corrosion (common in water-damaged vehicles), or physical damage to the processor chip causes the self-test program to fail.
  • 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
    Preliminary inspection: Use VDS or a dedicated diagnostic tool to read the complete 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, signs of water ingress, or a burnt smell. Inspect connector CA1 (or the corresponding vehicle connector) for looseness, and check the pins for oxidation or backing out. Measure the resistance at ground point G101 (or the corresponding ground point). The resistance must be less than 1Ω.
  • 3
    Power and communication check: Reconnect the battery and turn the ignition switch to ON. 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 about 2.5V) and the terminating resistance (about 60Ω) to rule out ECU malfunctions caused by network communication faults.
  • 4
    DTC verification: Clear the fault code, perform a road test or simulate a bump test, and observe if the fault returns. 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, perform the ECU software update following standard procedures. (Note: Connect an external regulated power supply and maintain a stable voltage above 13.5V during the update 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). After replacement, perform the following: ① Calibrate the crash sensor (use a spirit level to verify the vehicle is level); ② Write the VIN; ③ Set configuration parameters (e.g., vehicle model code, airbag configuration, seat belt type); ④ Cycle the ignition switch to confirm no fault codes are present and 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 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.