AU
U014604

DTC U014604 indicates a CAN communication timeout between the IPB (Integrated Brake Control System) and the Gateway controller — Atto 3

Braking System

DTC U014604 indicates a CAN communication timeout between the IPB (Integrated Brake Control System) and the Gateway controller.

In BYD new energy vehicles, the gateway acts as the core hub of the vehicle CAN network, coordinating data exchange among the Powertrain, Chassis, and Body networks.

The IPB system (one-box brake-by-wire solution) retrieves real-time vehicle status information via the gateway (e.g., motor torque, vehicle speed, regenerative braking requests, and VCU coordination commands) while simultaneously transmitting key data, such as brake pedal travel, wheel speed, and braking status, to other systems.

When a communication timeout occurs, the IPB enters a degraded protection mode.

This can cause regenerative braking failure, limit Electronic Stability Control (ESC) functionality, and cause Automatic Emergency Braking (AEB) to trigger falsely or fail.

In severe cases, the instrument cluster illuminates multiple warning lights, including ABS, ESC, and parking system indicators, compromising driving safety.

The U014604 fault code on the Atto 3 indicates a CAN communication timeout between the Integrated Brake Control System and the gateway controller. Severity is medium, as braking support systems such as regenerative braking, ESC, ABS, or AEB may be reduced or show warnings. Common causes include poor power or ground at the IPB or gateway, or a CAN wiring fault. 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 — Atto 3
  • 1Abnormal power supply or ground at the Gateway or IPB controller, including blown fuses, faulty relays, oxidized connectors, or backed-out pins causing unstable supply voltage.
  • 2CAN bus circuit fault, including CAN-H or CAN-L line open circuit, short circuit (to power, to ground, or to each other), excessive contact resistance, or abnormal terminating resistance (standard value: 60Ω±5Ω)
  • 3Internal control module fault, including damaged built-in CAN transceiver chip in the gateway or IPB, control program crash, or incompatible software version.
  • 4After driving through water or washing the vehicle, water ingress and corrosion at the gateway module connector, IPB connector, or floor wiring harness plug located beneath the center console interrupt signal transmission.
  • 5Installation of aftermarket electrical equipment (such as a dashcam drawing power from the OBD port, modified headlights, or an audio amplifier) causing CAN network signal interference or power supply fluctuations.
What To Do
  • 1
    Initial diagnosis: Use the dedicated diagnostic tool to read all vehicle fault codes. Record U014604 and accompanying fault codes (such as U014608, U0120). Check the vehicle for a history of water ingress, modifications, or accident repairs. Visually inspect the relevant connectors.
  • 2
    Power supply system check: Measure the constant power (B+), ignition power (IGN), and ground point voltages at the gateway module (usually under the center console or integrated into the BCM) and the IPB (in the engine compartment). Verify the voltages are within 12V±0.5V. Inspect fuse F2/15 (10A) and related fuses for good contact.
  • 3
    CAN bus static check: Disconnect the battery negative terminal. Measure the terminating resistance between pin 6 (CAN-H) and pin 14 (CAN-L) of the diagnostic connector (standard: 60Ω ± 5Ω). Measure the continuity of the CAN lines between the IPB and the gateway (<5Ω). Check for a short to ground or short to power.
  • 4
    Dynamic CAN signal monitoring: After power-on, use an oscilloscope or multimeter to measure the CAN-H (2.5-3.5V) and CAN-L (1.5-2.5V) voltage to ground. Observe the communication waveform to verify normal operation and check for signal interference.
  • 5
    Communication path test: Use the diagnostic tool to perform a gateway communication test. View the IPB communication status in the gateway node list and check if other modules have simultaneously lost communication with the IPB to determine whether the fault is on the gateway side or the IPB side.
  • 6
    Specific connector handling: Thoroughly inspect the gateway module connector (e.g., pin 12 CAN-H) and IPB connector for backed-out terminals, oxidation, or water ingress. If necessary, disassemble and clean, apply conductive grease, or replace the connectors.
  • 7
    Module verification and replacement: If wiring is normal but communication still fails, swap the gateway or IPB module from a known good identical vehicle for testing (note anti-theft matching and programming). If the fault transfers with the module, replace the corresponding control unit.
  • 8
    Software update: If hardware checks show no faults, update the gateway and IPB control software to the latest version to rule out software crashes or communication protocol mismatches.
  • 9
    Function check: After clearing the fault code, perform a road test under multiple operating conditions (including low speed, high speed, regenerative braking, and emergency braking) to verify U014604 does not return and all braking system functions operate normally.
Real-World Cases
BYD DTC AI Analysis

BYD Qin Series: Oxidized gateway connector causing communication timeout

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Instrument cluster displayed multiple system warning lights (powertrain, ESP, air conditioning, etc.). Scan tool read U0140 (similar to U014604 gateway communication fault) and multiple module communication errors. Technician checked the gateway module power supply and ground; voltage measured 12V±0.5V. CAN bus termination resistance measured 58Ω (normal). Further inspection found oxidation on the gateway module connector causing poor CAN signal contact. Cleaning the connector pins and applying conductive grease restored communication. DTCs cleared and did not return. This case shows connector oxidation is a common cause of gateway communication faults.
Original source ↗
BYD DTC AI Analysis

CAN-H Line Break Causes Gateway Communication Fault in BYD HA

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While driving, the ABS, ESP and SRS warning lights intermittently lit up simultaneously with power limitation. Scanned DTCs U027004, U057108, U012004, U046908 and other CAN communication faults (same timeout category as U014604). Technicians measured the CAN bus voltage and found abnormal readings. Further resistance testing between the ESP node and gateway found the CAN-H line broken at the firewall (infinite resistance). They re-soldered the harness and applied waterproof insulation, eliminating the fault. In another similar case, poor contact at the ESP node power supply fuse holder caused the issue; cleaning the holder resolved it.
Original source ↗
BYD DTC AI Analysis

Song PLUS DM-i U014604 Gateway Communication Timeout - Pin Retraction Repair

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Vehicle failed to start; dashboard displayed "Check Powertrain". Scan tool read U014604 (Gateway Communication Timeout) and U014608 (BCM Data Length Error). CAN line continuity between gateway and BCM checked normal. BCM supply voltage (B+, IGN) and ground measured normal. Removed gateway module connector and found pin 12 (CAN-H) had backed out, interrupting communication with the IPB system. Re-secured the pin to ensure good contact, cleared fault codes, and vehicle started normally. In another similar case, driving through water caused internal PCB corrosion in the gateway module, requiring replacement and reprogramming.
Original source ↗
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.