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U01000B

U01000B is a CAN communication fault code for BYD e-Platform 3 — Atto 3

Braking System

U01000B is a CAN communication fault code for BYD e-Platform 3.0 models (such as the Seal 6 DM-i and Song PLUS DM-i).

This fault code indicates the IPB (Integrated Intelligent Braking System) detects a data integrity error when receiving the 0x240 message from the VCU (Vehicle Control Unit).

Specific errors include incorrect message byte length, CRC (Cyclic Redundancy Check) errors, non-continuous or abnormal Alive Counter jumps, or key signal values exceeding the valid range.

This powertrain CAN network communication fault may limit regenerative braking, cause abnormal electro-hydraulic braking coordination, and in severe cases, trigger the braking system degraded protection mode, compromising driving safety.

5
Cases Logged
Real-World Cases
BYD DTC AI Analysis

Intermittent brake system warning light on Seal 6 DM-i instrument cluster

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A 2024 Seal 6 DM-i with 8,500 km. The owner reported the brake system warning light occasionally illuminating on the instrument cluster with the message "Please check brake system". VDS scan revealed the IPB system stored DTCs U01000B (FM Data Corruption 6) and U010087 (VCU Communication Timeout). Freeze frame data showed the fault occurred at approximately 60 km/h. Checked the CAN wiring harness between the VCU and IPB; found a retaining clip detached at the left front chassis rail. The harness had chafed against a sharp body edge, damaging the CAN-H wire insulation and causing an intermittent short. Repaired the harness and resecured it; fault resolved.
Original source ↗
BYD DTC AI Analysis

Song PLUS DM-i Stiff Brake Pedal Fault

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While driving, a 2021 Song PLUS DM-i suddenly displayed "Brake System Fault" and "ESP Fault" on the instrument cluster, and the brake pedal became hard. VDS showed IPB codes U01000B and C123456 (hydraulic unit fault). Inspection found outdated VCU software (early versions have a 0x240 message counter jump defect) and oxidation on IPB ground wire G104. Cleaned the ground connection and upgraded the VCU to the latest software version (Ver 3.2.1). The fault has not returned.
Original source ↗
BYD DTC AI Analysis

Dolphin unable to enter OK mode and reports communication fault.

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A 2023 Dolphin failed to enter Ready mode after being parked overnight, with the instrument cluster showing multiple system faults. VDS scanning revealed the IPB, BMS, and MCU all reported communication faults with the VCU; the IPB logged U01000B. CAN bus voltage measurement showed CAN-H shorted to ground (0.2V). Sectional troubleshooting isolated water ingress in the VCU connector from high-pressure washer spray during cleaning, causing corrosion and a short in the CAN-H pin. Cleaned and dried the VCU connector, confirmed normal insulation, and resolved the fault. Check engine bay sealing.
Original source ↗
BYD DTC AI Analysis

Seal EV loss of power while driving with brake warning

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A 2022 Seal EV experienced intermittent power loss during high-speed driving. The dashboard displayed "Check connector" and "Braking system fault" warnings. VDS retrieved IPB history DTC U01000B (FM data corruption 6). Checking the VCU power supply found burnt contacts on the IG1 ignition relay, causing the VCU to intermittently lose power and restart. The 0x240 message sent during the restart was incomplete. Replaced the IG1 relay in the engine bay fuse box and inspected the VCU power management module. Fault resolved.
Original source ↗
BYD DTC AI Analysis

Song Pro DM-i sets data corruption fault after IPB replacement

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A 2022 Song Pro DM-i had its IPB assembly replaced due to brake noise. Post-repair, VDS scanning showed DTC U01000B (FM data corruption 6) that would not clear. Inspection revealed the replacement IPB (part number SC2E-3550100, low-spec version) was incompatible with the original SC2E-3550100A (high-spec with ACC), causing CAN message parsing errors. After installing the correct IPB and performing online configuration and sensor calibration, the fault codes cleared and brake system operation returned to normal.
Original source ↗
Other Atto 3 Fault Codes
P0A0DBattery Energy Control Module Requested MIL IlluminationP0AA6Hybrid Battery Voltage System Isolation FaultP1A00Drive Motor "A" Performance — BYD proprietaryB1108For 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.
Data confidence: Community This information is for reference only. Always consult a qualified technician for diagnosis and repair. Do not attempt high-voltage system repairs yourself.