AU
U014604

DTC U014604 indicates a CAN communication timeout between the IPB (Integrated Brake Control System) and the Gateway controller — Atto 8

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.

3
Cases Logged
5
Causes
Likely Causes — Atto 8
  • 1Gateway or IPB controller power supply/ground fault, including blown fuses, relay failures, connector oxidation, or terminal back-out 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 terminal resistance (standard value: 60Ω±5Ω).
  • 3Internal control module fault, including a 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 under the center console interrupts signal transmission.
  • 5Installing aftermarket electrical equipment (such as dash cams drawing power from the OBD port, modified headlights, or audio amplifiers) causes 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 any 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 located under the center console or integrated into the BCM) and the IPB (located in the engine compartment). Verify the voltages are within 12V±0.5V. Check fuse F2/15 (10A) and related fuses for good contact.
  • 3
    CAN bus static inspection: Disconnect the battery negative terminal. Measure the terminating resistance between pins 6 (CAN-H) and 14 (CAN-L) of the diagnostic connector (standard: 60Ω ± 5Ω). Measure CAN line continuity between the IPB and the gateway (<5Ω). Check for a short to ground or power.
  • 4
    Dynamic CAN signal monitoring: After power-on, use an oscilloscope or multimeter to measure CAN-H (2.5-3.5V) and CAN-L (1.5-2.5V) voltage to ground. Observe the communication waveform to verify it is normal and check for signal interference.
  • 5
    Communication path test: Use the diagnostic tool to perform a gateway communication test. Check the IPB communication status in the gateway node list and verify if other modules simultaneously lost communication with the IPB to determine whether the fault is on the gateway side or the IPB side.
  • 6
    Connector handling: Inspect the gateway module connector (e.g., pin 12 CAN-H) and IPB connector for terminal back-out, 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, test by swapping the gateway or IPB module from a known good identical vehicle (note anti-theft matching and programming). If the fault transfers with the module, replace the corresponding control unit.
  • 8
    Software update: If hardware checks are normal, update the gateway and IPB control software to the latest version to eliminate software crashes or communication protocol mismatches.
  • 9
    Function check: After clearing the fault code, perform a multi-condition road test (including low speed, high speed, regenerative braking, and emergency braking). 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

✓
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

✓
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

✓
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 8 Fault Codes
B1108For 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.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.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.
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.