AU
U0146

DTC U0146 indicates a loss of communication between the airbag control unit (SRS ECU) and the vehicle gateway controller (Gateway Control Module) — Atto 8

Safety System

DTC U0146 indicates a loss of communication between the airbag control unit (SRS ECU) and the vehicle gateway controller (Gateway Control Module).

The gateway acts as the data exchange hub between different vehicle CAN bus networks (such as powertrain CAN, comfort CAN, and chassis CAN) and routes information between control units.

When the SRS system cannot communicate with the gateway, the airbag system becomes isolated.

It cannot receive critical signals from other systems (such as crash signals, vehicle speed signals, and high-voltage interlock status).

Additionally, during a collision, it cannot send commands through the gateway to other systems (such as cutting off the high-voltage power supply, unlocking the doors, and turning on the hazard lights).

This may degrade or disable crash protection functions, creating a serious safety hazard.

The U0146 fault code on the Atto 8 indicates a loss of communication between the airbag control unit and the gateway control module. This is a medium-severity issue because it can affect airbag-related crash protection and emergency response functions. Common causes include gateway power or ground faults, or damaged CAN bus wiring. The recommended fix is to visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
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Cases Logged
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Causes
Likely Causes — Atto 8
  • 1Gateway Controller (GWC) power supply or ground circuit fault causing intermittent or permanent power loss to the gateway.
  • 2Physical damage to the CAN bus wiring (chafing, crushing, water ingress) causing a short circuit, open circuit, or excessive contact resistance in CAN-H and CAN-L.
  • 3Gateway controller internal hardware fault or outdated software version causing a communication protocol mismatch.
  • 4Airbag Control Unit (SRS) internal communication module fault or poor connector contact
  • 5Unauthorized vehicle modifications (such as connecting aftermarket navigation systems or dash cams to the CAN network) causing signal interference or excessive bus load.
What To Do
  • 1
    Perform a full vehicle scan using the VDS2000/VDS1000 diagnostic tool. Record the communication status and fault codes of all modules, and determine whether the communication fault affects a single module or multiple modules.
  • 2
    Check the power supply (constant BATT, ignition IG1) and ground (GND) of the gateway controller (usually located under the dashboard or center tunnel). Measure the voltage; it must be within 12V±0.5V, and ground resistance must be less than 1Ω.
  • 3
    Measure the voltage at diagnostic connector (OBD) pin 6 (CAN-H) and pin 14 (CAN-L). Normal voltages are 2.5V-2.7V and 2.3V-2.5V respectively. Measure the terminal resistance. It should be approximately 60Ω (two 120Ω resistors in parallel).
  • 4
    Inspect the CAN wiring harness between the SRS control unit and the gateway, focusing on wear-prone areas such as the firewall, A-pillar, and floor harness pass-through holes. Check the connectors for water ingress, oxidation, or looseness.
  • 5
    Disconnect the negative battery terminal. Measure the CAN terminating resistance at the SRS and gateway respectively (if equipped). Check for open or short circuits.
  • 6
    Check the gateway and SRS software versions. If a Technical Service Bulletin (TSB) recommends an upgrade, update the software.
  • 7
    If the wiring is normal, perform a substitution test: first replace the gateway controller and test. If the fault persists, replace the SRS control unit (synchronize the immobilizer and match the airbag coding).
  • 8
    After repair, clear the fault code, perform a road test, and rescan to confirm communication is restored and the fault code does not return.
Real-World Cases
BYD DTC AI Analysis

BYD Song - Multi-system network fault (including communication faults similar to U0146)

✓
Symptoms: While driving, the dashboard suddenly displayed multiple warnings: "Check Engine System", "ABS System", "Network", and "Brake System". Vehicle performance restricted. Diagnosis: Scanned with VDS1000. Found ECM stored communication fault codes related to the Body Control Module. Checked CAN network voltage and termination resistance; resistance was below standard (60Ω). Inspected the CAN harness section by section and found wiring below the right A-pillar worn through, shorting CAN-H and CAN-L. Resolution: Repaired the damaged CAN harness below the right A-pillar, re-wrapped and insulated the wiring, cleared fault codes, and road-tested. All system communications returned to normal.
Original source ↗
BYD DTC AI Analysis

BYD Qin 80 - CAN network failure causing no-start condition (U0146-type fault)

✓
Symptoms: Intermittent flashing P gear indicator, no SOC display. Instrument cluster showed multiple system warnings including "Check ESP System" and "Check EPB System." Vehicle would not enter Ready mode. Diagnosis: Vehicle was normal on arrival, confirming intermittent fault. No modifications or aftermarket accessories found. VDS scan showed multiple modules reporting communication errors, including abnormal communication with the left body domain controller. Measured CAN voltage at diagnostic port: CAN-H 2.3V, CAN-L 2.7V (normal ~2.5V). Sectional testing found water ingress in the left front door wiring harness connector causing abnormal CAN signals. Resolution: Cleaned water from left front door wiring harness connector, applied conductive grease, and resecured waterproof seal. Fault cleared.
Original source ↗
BYD DTC AI Analysis

BYD Tang DM - All dashboard warning lights intermittently illuminate (network communication fault)

✓
Symptoms: While driving, all instrument warning lights intermittently illuminated, the speedometer went blank, and power steering assist dropped out. Restarting did not help; the system sometimes recovered after sitting idle. Diagnosis: Scanned with VDS and found multiple modules simultaneously reporting communication faults. Checked pin 16 (power) and pins 4/5 (ground) at the OBD port — supply checked normal. Measured the CAN waveform and found abnormal noise. Disconnected modules one by one; disconnecting the smart entry controller cleared the fault. Power and ground at the smart entry controller checked normal. Replaced the controller and verified the CAN waveform returned to normal. Resolution: Replaced the smart entry controller, rematched the immobiliser, and eliminated the fault.
Original source ↗
BYD DTC AI Analysis

BYD Song Pro - Dashboard displaying 'Key Not Detected' (network communication fault)

✓
Symptoms: Rotating PAD screen stayed on constantly. Attempted to restart vehicle but failed. Instrument panel displayed "Key Not Detected." Remote key unresponsive. Diagnosis: No modifications or aftermarket accessories found. VDS scan showed multiple modules offline, including intermittent BCM (Body Control Module) communication. Measured BCM supply voltages: constant 12V normal; IG1 dropped to 9.5V. Checked IG1 power circuit between instrument panel fuse box and BCM; found poor contact at intermediate connector. Wiggling the wiring harness caused BCM communication to drop in and out. Fix: Cleaned and tightened IG1 power connector between instrument panel fuse box and BCM, replaced corroded terminals. Fault cleared.
Original source ↗
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.