AU
U014008

DTC U014008 indicates a CAN data communication integrity check failure between the ABS/ESC control unit and the vehicle gateway controller — Atto 8

Braking System

DTC U014008 indicates a CAN data communication integrity check failure between the ABS/ESC control unit and the vehicle gateway controller.

Data frames sent by the ABS module to the gateway over the Powertrain CAN bus contain CRC errors, out-of-sequence frames, abnormal Data Length Codes (DLC), or protocol format mismatches.

Consequently, the gateway determines the received brake system status data is corrupted.

This fault triggers the brake system fail-safe strategy, degrading or completely disabling functions such as ABS, ESC, EBD, and Autonomous Emergency Braking (AEB).

Simultaneously, the gateway sends multi-system fault warnings to the instrument cluster, severely compromising driving safety.

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Cases Logged
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Causes
Likely Causes — Atto 8
  • 1Internal CAN transceiver chip failure or software checksum algorithm error in the gateway controller prevents it from correctly parsing ABS data frames.
  • 2Physical damage (abrasion, crushing) to the Power CAN line between the ABS/ESC control unit and the gateway, water ingress and oxidation in the connector, or excessive contact resistance, compromising signal integrity.
  • 3ABS/ESC module software bug (e.g., calibration defect in early E5 versions) or internal CAN controller hardware fault continuously sending incorrectly formatted data frames.
  • 4Unstable power supply voltage to the gateway controller (battery voltage below 10V or above 16V, or poor grounding) causes a data processing timing error.
  • 5Strong electromagnetic interference (such as high-voltage power distribution system insulation faults or non-OEM retrofitted electrical equipment) distorts the CAN bus signal.
What To Do
  • 1
    Use the VDS2000/VDS3000 diagnostic tool to read the complete DTC list. Confirm whether U014008 is a current (Active) or historical (History) fault code, and record freeze frame data parameters such as vehicle speed, voltage, and temperature.
  • 2
    Check the power supply voltage (constant B+, ignition IG1 power) and ground resistance of the gateway controller (on the BYD E5, typically below the left side of the dashboard or near the front compartment power distribution box) and the ABS module. Verify ground resistance is less than 1Ω and voltage is 12-14V.
  • 3
    Measure the terminal resistance between OBD diagnostic connector pins 6 (CAN-H) and 14 (CAN-L) (standard value: approx. 60 Ω; measure with power off). Check the CAN line dynamic voltage (CAN-H: 2.5-3.5 V, CAN-L: 1.5-2.5 V). Use an oscilloscope to check the waveform for symmetry and noise.
  • 4
    Inspect the CAN wiring harness connectors between the gateway and the ABS (e.g., BJ01, G04, G05) for water ingress, corrosion, terminal back-out, or poor contact. If necessary, clean the connectors with electrical contact cleaner and apply conductive grease. Verify the protection rating meets specifications.
  • 5
    Update the control unit software: Flash the latest calibration files to the gateway controller and ABS/ESC module (Note: E5 2018-2019 models must use ABS software version V2.8 or higher to fix an early communication protocol bug).
  • 6
    If the fault persists, verify by substitution: First, replace the gateway controller (part number 6A-3600010 or similar). If this fails, replace the ABS/ESC assembly (Note: Code and match the new module, and calibrate the steering angle sensor).
Real-World Cases
BYD DTC AI Analysis

2018 BYD E5 – Gateway module water ingress corrosion caused data validation failure

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2018 E5, 80,000 km. ABS and ESC warning lights illuminated after driving in rain. Fault code U014008. The gateway controller, mounted under the left side of the dashboard, had water ingress from a perished windscreen seal that corroded the circuit board. CAN bus voltage between the gateway and ABS measured normal, but the internal CAN transceiver chip (TJA1043) output distorted waveforms. Replaced the gateway controller and sealed it; also replaced the windscreen seal to prevent recurrence. Fault resolved.
BYD DTC AI Analysis

E5 ABS pump assembly CAN chip damaged, continuously transmitting error frames

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The vehicle failed to engage high voltage; the instrument cluster displayed a brake system fault. The scanner read DTC U014008, which would not clear. Power and ground at the ABS module were normal, but scoping the ABS-side CAN bus revealed heavy error frames. Removed and disassembled the ABS pump assembly; the internal CAN transceiver chip was damaged from overvoltage, continuously transmitting malformed packets and causing the gateway to flag the data as corrupt. Replaced the ABS/ESC assembly and performed calibration. Fault resolved.
BYD DTC AI Analysis

Wiring harness chafing caused a CAN-H short to ground, resulting in an intermittent fault.

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ABS warning light occasionally illuminated when driving on rough roads; normal on smooth surfaces. Read DTC U014008 (intermittent). Inspection found ABS wiring harness in engine bay rubbing against engine mount, with worn insulation causing intermittent CAN-H short-to-ground. When shorted, ABS data signals pulled low, resulting in CRC checksum failures on packets received by gateway; data flagged as corrupt. Re-routed harness and fitted protective sleeving, insulated worn sections. Fault eliminated.
BYD DTC AI Analysis

Software version mismatch caused protocol parsing error

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A 2019 E5 repaired after an accident kept setting U014008 after a second-hand ABS pump was installed. Check showed the replacement was an early hardware revision with software calibration incompatible with the vehicle gateway protocol (data frame length definition mismatch). Hardware part numbers matched, but the software was too old (V2.3). Flashed the ABS module to V2.9; the protocols aligned, the fault code cleared automatically, and all braking functions returned to normal.
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.