AU
U014604

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

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 Seal U indicates a CAN communication timeout between the Integrated Brake Control System (IPB) and the Gateway controller. This is a medium-severity fault that may reduce regenerative braking, ESC, or AEB functions. Common causes include unstable power or ground to the IPB/Gateway, or CAN wiring faults such as open circuits, shorts, or high resistance. Visit an authorised dealer for diagnosis and repair. Typical repair cost data is available from recorded cases.
3
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Abnormal power supply or ground for the Gateway or IPB controller, including blown fuses, relay faults, 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 shorted together), 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.
  • 4Driving through water or washing the vehicle causes water ingress and corrosion at the gateway module connector, IPB connector, or floor wiring harness plug located under the center console, interrupting signal transmission.
  • 5Installation of aftermarket electrical equipment (such as OBD-powered dash cams, modified headlights, or audio amplifiers) 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 (e.g., U014608, U0120). Check the vehicle history for 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 of 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. 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 diagnostic connector pins 6 (CAN-H) and 14 (CAN-L) (standard: 60Ω±5Ω). Measure CAN line continuity between the IPB and the gateway (<5Ω). Check for shorts to ground or power.
  • 4
    Dynamic CAN signal monitoring: After power-on, use an oscilloscope or multimeter to measure the voltage to ground for CAN-H (2.5-3.5V) and CAN-L (1.5-2.5V). 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 check if other modules simultaneously lost communication with the IPB to determine if the fault is on the gateway side or the IPB side.
  • 6
    Connector handling: Carefully 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, swap the gateway or IPB module from a known good identical vehicle to test (note anti-theft matching and programming). If the fault transfers with the module, replace the corresponding control unit.
  • 8
    Software update: If hardware checks reveal no faults, flash the gateway and IPB control programs to the latest version to rule out software crashes or communication protocol mismatches.
  • 9
    Function verification: After clearing the fault code, perform a road test under multiple 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

✓
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

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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 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.