AU
U0146-00

DTC U0146-00 indicates a Controller Area Network (CAN) communication interruption between the airbag control unit (SRS ECU) and the vehicle gateway module — Atto 3

Safety System

DTC U0146-00 indicates a Controller Area Network (CAN) communication interruption between the airbag control unit (SRS ECU) and the vehicle gateway module.

In BYD Qin series models, the Body Control Module (BCM) typically integrates the gateway, coordinating data exchange among the powertrain CAN, comfort CAN, and chassis CAN.

The system triggers this fault when the SRS fails to receive the gateway handshake signal or data frame within the specified cycle (typically 250ms).

This forces the airbag system into a degraded mode, preventing normal airbag deployment, seatbelt pretensioning, or high-voltage cutoff activation during a collision.

It may also affect the vehicle’s collision signal recording function.

This network communication fault does not involve electrical failures within the SRS components themselves, but it directly disables the passive safety system.

The U0146-00 fault code on the Atto 3 indicates a CAN communication interruption between the airbag control unit and the vehicle gateway module. Severity is medium because the airbag system may enter a degraded mode and passive safety functions may not work correctly. Common causes include poor power or ground to the gateway/BCM, or an open/short in the CAN wiring. The recommended fix is to visit an authorised dealer. Typical repair cost data is available.
4
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Gateway module (BCM) power supply circuit fault: Poor contact in the constant power (B+), ignition power (IG), or ground wire, or a blown fuse, preventing normal gateway operation.
  • 2CAN network circuit fault: Open or short circuit in the CAN-H and CAN-L wiring harness between the SRS and gateway, or terminating resistor drift (normal: 60Ω), causing signal transmission failure.
  • 3Internal gateway module fault: Damaged BCM internal CAN transceiver, software crash, or lost configuration data prevents SRS data frame forwarding.
  • 4SRS control unit connector issue: Loose airbag control module plug, oxidized pins, or backed-out pins. Poor contact commonly occurs after driving through water, exposure to high humidity, or center console removal and installation.
  • 5Electromagnetic interference or abnormal voltage: Aftermarket electronic equipment (such as dash cams or navigation systems) interferes with the CAN signal, or unstable battery voltage (below 9V or above 16V) interrupts communication.
What To Do
  • 1
    Full diagnostic scan: Use the VDS2000/VDS3000 diagnostic tool to read all vehicle DTCs. Check for accompanying codes such as U0100 (lost communication with engine) or U0121 (lost communication with ABS) to determine if the issue is a single system fault or a gateway bus failure. Verify the SRS software version is up to date.
  • 2
    Power and ground check: Measure the constant power (B+, should be 12V), ignition power (IG, should be 12V in the ON position), and ground resistance (should be <1Ω) at the gateway module (located below the left side of the dashboard). Check for blown SRS-related fuses (such as F1/15 and F2/3) in the dashboard fuse box.
  • 3
    CAN harness inspection: Disconnect the SRS control unit (located beneath the centre tunnel) and the gateway connector. Measure the resistance between CAN-H and CAN-L (should be 60±5Ω) and the voltage to ground (CAN-H 2.5-3.5V, CAN-L 1.5-2.5V). Check the harness for abrasion or crushing (focus on centre tunnel removal and installation history).
  • 4
    Connector and terminal inspection: Check the SRS connector (32-pin, usually blue) and gateway connector (40-pin) pins for oxidation, backed-out pins, or spread terminals. Clean with electrical contact cleaner. Verify the locking mechanism is intact. Replace the terminals using a wiring harness repair tool if necessary.
  • 5
    Module replacement and programming: After ruling out wiring faults, swap the gateway module or SRS module with a unit of the same model for testing (ensure the configuration coding matches). Use the diagnostic tool to flash the gateway configuration parameters (Coding), perform SRS system calibration, clear the fault codes, and perform a drive cycle test (at least 3 ignition cycles, including low-speed driving).
Real-World Cases
BYD DTC AI Analysis

2017 Qin EV300: Oxidized gateway ground point causing intermittent communication failure

✓
After driving through water, the airbag warning light came on. The scan tool retrieved U0146-00 and multiple communication fault codes. Inspection found severe oxidation at the gateway module (BCM) ground point G301 (located on the body below the left A-pillar) caused by water ingress, with ground resistance measuring 15Ω (specification <1Ω). The gateway connector also showed traces of water. Repair: Thoroughly cleaned ground point G301 and applied conductive anti-corrosion paste, dried the gateway connector, and used compressed air to clean the pins. Post-repair CAN line resistance measured 59.8Ω, communication returned to normal, and the warning light went out. Check the vehicle weatherstrip seals and drain holes for blockages.
BYD DTC AI Analysis

2017 BYD Qin 100: CAN wiring harness pinched and shorted after accident repair

✓
After front-end collision repairs, the SRS warning light stayed on. Read DTC U0146-00. Found the technician trapped the SRS control unit wiring harness (behind the gear selector) between the metal bracket and plastic trim panel during center console removal, damaging the CAN-H wire insulation and causing a short to ground. Repair: Released the harness, repaired the damaged CAN-H wire (pink/green) with double-layer heat shrink tubing, rerouted the wiring to avoid sharp metal edges per standard, and adjusted the harness clip positions. Cleared fault codes; SRS system passed self-test.
BYD DTC AI Analysis

2018 Qin EV450: Oxidized SRS connector pins causing poor contact

✓
Two-year-old vehicle used in a coastal city. Airbag warning light illuminates intermittently and clears after cycling the ignition. Scan tool reads intermittent fault code U0146-00. Inspection revealed prolonged high-humidity exposure. Pins 15 (CAN-H) and 16 (CAN-L) on the 32-pin SRS control unit connector (beneath the centre console) showed severe green corrosion. The connector locking tab was loose. Repair: Cleaned the connector with precision electronics cleaner, sanded the oxidised pins with fine sandpaper, applied conductive grease, and replaced the connector housing (repair kit), ensuring the lock engages properly. Advised the owner to regularly check for carpet dampness and replace the air conditioning desiccant if required.
BYD DTC AI Analysis

2017 BYD Qin 80: Retrofitted dashcam caused CAN bus signal interference

✓
The owner fitted a 12V-to-5V step-down cable for the dashcam, incorrectly tapping power from the OBD diagnostic port. After some time, the airbag warning light came on with intermittent instrument cluster blackouts. Diagnosis found DTCs U0146-00 and U0155 (lost communication with instrument cluster). Inspection showed the step-down cable was poor quality, generating high-frequency electromagnetic interference that coupled into the CAN network through the power lines. Fix: Removed the OBD tap and rewired to the fuse box ACC supply, adding a ferrite ring to the power lead. Used an oscilloscope to confirm no abnormal spikes in the CAN waveforms. Cleared the fault codes and the system returned to normal. Advised the owner to avoid poor-quality electronic devices.
Other Atto 3 Fault Codes
P0AA6Hybrid Battery Voltage System Isolation FaultB1108For 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.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.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.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.
Common problems reported for Atto 3 →Atto 3 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.