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 — Seal U

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 Seal U indicates a CAN communication interruption between the airbag control unit and the vehicle gateway module. Severity is medium because it can put the airbag system into degraded mode and affect crash safety functions. Common causes include BCM/gateway power or ground faults, blown fuses, or damaged CAN wiring. The recommended fix is to visit an authorised dealer for diagnosis and repair. Typical repair cost data is available.
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Cases Logged
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Causes
Likely Causes — Seal U
  • 1Gateway module (BCM) power supply circuit fault: Includes poor contact in the constant power supply (B+), ignition switch power supply (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 forwarding of SRS data frames.
  • 4SRS control unit connector issue: Loose airbag control module plug, oxidized pins, or backed-out pins. Poor contact frequently occurs after wading, exposure to high humidity, or center console removal and installation.
  • 5Electromagnetic interference or abnormal voltage: Aftermarket electronic devices (such as dash cams or navigation units) interfere with CAN signals, 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 this is a single system fault or a gateway bus failure. Verify the SRS software 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) of the gateway module (located below the left side of the instrument panel). Check if the SRS-related fuses (such as F1/15 and F2/3) in the instrument panel power distribution box are blown.
  • 3
    CAN harness inspection: Disconnect the SRS control unit (located beneath the center 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, focusing on the center tunnel removal and installation history.
  • 4
    Connector and terminal inspection: Check the pins on the SRS connector (32-pin, usually blue) and the gateway connector (40-pin) for oxidation, backed-out terminals, or enlarged contacts. 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 eliminating wiring faults, swap the gateway module or SRS module with a unit of the same model for testing (verify the configuration coding matches). Use the diagnostic tool to program the gateway configuration parameters (Coding), perform SRS system calibration, clear the fault codes, and execute 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

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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

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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

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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 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.