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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.

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Cases Logged
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

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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
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
Data confidence: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.