AU
B169800

DTC B169800 indicates an internal fault or communication failure in the airbag control unit (SRS ECU) — Seal U

Safety System

DTC B169800 indicates an internal fault or communication failure in the airbag control unit (SRS ECU).

As the core control module of the airbag system, the SRS ECU monitors crash sensor signals, processes crash algorithms, and controls airbag and seat belt pretensioner deployment.

This DTC indicates the ECU self-check detected an internal processor fault, memory error, power supply fault, or CAN communication interruption with other modules (such as the Vehicle Control Unit or Body Control Module).

This fault poses a severe safety risk and may cause the airbags to fail to deploy or to deploy inadvertently during a collision.

Repair immediately.

4
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Poor contact in the SRS ECU power supply or ground circuit, or abnormal voltage (below 9V or above 16V)
  • 2SRS ECU internal hardware fault (damaged processor, memory, or internal sensor)
  • 3CAN bus communication fault (communication interrupted between the SRS ECU and vehicle network, or signal interference)
  • 4Outdated SRS ECU software version or missing/corrupted calibration data.
  • 5Short or open circuit in the communication line between the crash sensor and the SRS ECU.
What To Do
  • 1
    Use BYD VDS or a dedicated diagnostic tool to read the complete fault codes and freeze frame data. Confirm if B169800 is a current or historical fault. Check for accompanying communication fault codes (such as codes starting with U).
  • 2
    Check the instrument panel SRS warning light status (steady or flashing). Disconnect the negative battery terminal for 5 minutes, then restore power. Perform a system self-check and observe whether the fault code returns.
  • 3
    Check the SRS ECU power supply and ground: Measure the voltage and resistance at ECU connector terminal 1 (constant power B+), terminal 2 (ignition switch power IG), and the ground terminal. Verify the voltage is 9-16V and the ground resistance is less than 1Ω.
  • 4
    Check CAN bus communication: Measure CAN-H and CAN-L voltages at the diagnostic connector or SRS ECU connector (CAN-H approx. 2.6-2.8V, CAN-L approx. 2.2-2.4V) and terminating resistance (approx. 60Ω) to rule out wiring short or open circuits.
  • 5
    Check the SRS ECU connector and wiring harness: Inspect for water ingress, corrosion, bent pins, backed-out pins, or harness damage. Pay special attention to wiring harness connections after front-end collision repairs.
  • 6
    If the wiring is normal, perform an SRS ECU software upgrade or reprogramming using the latest software version. If the fault persists, replace the SRS ECU assembly. After replacement, perform online programming, configuration code writing, and a system self-check.
Real-World Cases
BYD DTC AI Analysis

BYD Qin Pro EV: SRS warning light came on while driving, logged DTC B169800

✓
The SRS warning light on the dashboard suddenly came on while driving normally. Connected a VDS diagnostic tool and read current fault code B169800 (SRS ECU fault) and stored fault U0155 (lost communication with instrument cluster). Inspection revealed the vehicle had recently had an aftermarket audio system installed, and the centre console had been removed and reinstalled. Removed and inspected the SRS ECU, located under the centre console on the central tunnel, and found the ECU power connector not fully seated, causing intermittent power loss from vibration while driving. Reseated the connector and secured the wiring harness. Cleared the fault codes; the SRS light went out. Road tested for 50 km with no recurrence of the fault.
Original source ↗
BYD DTC AI Analysis

BYD Han EV reports DTC B169800 after accident repair; code will not clear.

✓
Front-end collision. Replaced front bumper and impact sensors. After repairs, airbag warning light stayed on. Read DTC B169800. Inspection found slight deformation of the SRS ECU housing, no cracks. Measured ECU power supply and ground: normal. CAN communication: normal. ECU internal self-test failed. Determined shock wave from collision damaged internal accelerometer or processor in SRS ECU. Replaced with new SRS ECU. Performed online programming via VDS, wrote VIN and configuration parameters. Ran system self-test: passed. Fault cleared.
Original source ↗
BYD DTC AI Analysis

BYD e2 intermittently reports SRS ECU fault

✓
The owner reported the SRS warning light occasionally comes on, sometimes clearing after cycling the ignition. The diagnostic scanner retrieved intermittent DTC B169800. Inspection found the vehicle had been through water, with water accumulation marks at the SRS ECU mounting bracket beneath the floor. Removed the ECU and found slight oxidation inside the connector. Cleaned the ECU and harness connectors, dried internal moisture with compressed air, and applied electrical contact protectant. Also found the ECU ground wire attachment point rusted; sanded the ground terminal and retightened. Followed up for one month post-repair, no recurrence.
Original source ↗
BYD DTC AI Analysis

BYD Tang DM sets DTC B169800 after battery pack replacement

✓
After replacing the power battery pack at the dealership, the airbag warning light illuminated during handover. Retrieved DTC B169800. Investigation found the 12V battery had been disconnected for too long during the repair, and the technician had disconnected the SRS ECU connector to gain access. A communication timeout occurred after reconnection. Performed SRS reconfiguration and calibration using VDS, cleared the DTC, and the system returned to normal. Root cause: ECU data loss after power disconnection, requiring system reconfiguration.
Original source ↗
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.