AU
U01000A

DTC U01000A indicates the Intelligent Integrated Brake System (IPB) or vehicle network detects an integrity check failure or abnormal data content in Engine Control Module (ECM) data packets during CAN communication — Atto 8

Braking System

DTC U01000A indicates the Intelligent Integrated Brake System (IPB) or vehicle network detects an integrity check failure or abnormal data content in Engine Control Module (ECM) data packets during CAN communication.

Unlike a simple loss of communication (U0100), this fault indicates a normal physical connection where ECM-transmitted data frames contain CRC errors, data overflows, illegal values, or sequence anomalies.

Causes include ECM internal memory (RAM/ROM) faults, program runaway, a damaged CAN transceiver, or strong electromagnetic interference.

In the DM-i hybrid architecture, abnormal ECM data prevents the IPB from accurately acquiring engine torque, speed, and operating status.

This directly affects the brake energy recovery strategy, ABS/ESP coordinated control, and overall vehicle power distribution, posing a safety hazard.

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Cases Logged
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Causes
Likely Causes — Atto 8
  • 1Defective ECM software version or corrupted calibration data causing periodic transmission of incorrect data frames.
  • 2Unstable ECM supply voltage (burnt main relay contacts, increased battery internal resistance, poor ground connection), causing abnormal module operation or reset.
  • 3Electromagnetic interference, physical damage to the wiring harness, or abnormal terminating resistance on the powertrain CAN bus (PT-CAN) causes data transmission errors.
  • 4Internal ECM hardware fault (damaged CPU, memory, or CAN transceiver chip)
  • 5Water ingress, oxidation, backed-out terminals, or seal failure at the engine compartment wiring harness connectors (especially the ECM connector), compromising signal integrity.
What To Do
  • 1
    Use the BYD VDS diagnostic tool to read the complete fault codes and freeze frame data. Check if U01000D (ECM communication timeout), U010001, or other communication faults accompany this code. Record environmental parameters such as vehicle speed and voltage when the fault occurred.
  • 2
    Check the ECM basic power supply and ground: Measure constant power (B+), ignition switch power (IG), and the main ground point. Verify the voltage is stable at 12V±0.5V and ground resistance is less than 1Ω. Check if the ECM main relay engages normally and inspect the contacts for burning.
  • 3
    Check the powertrain CAN bus: Measure CAN-H (2.6V±0.2V) and CAN-L (2.4V±0.2V) static voltages. Verify the terminal resistance between the bus lines is 60Ω±5Ω. Use an oscilloscope to observe the dynamic waveform and check for abnormal pulses or spikes.
  • 4
    Visually inspect the ECM wiring harness connector: check for sealing ring aging, signs of water ingress, or pin oxidation (green corrosion). If necessary, clean with electrical contact cleaner and apply special conductive grease. Fully seat the connector.
  • 5
    Perform ECM software update: Connect the diagnostic tool and upgrade the ECM to the latest software version. Clear the fault code, then perform a 20-30 minute road test (including hard acceleration, braking, and hybrid mode switching) to confirm if the fault reoccurs.
  • 6
    If the fault persists, measure the continuity of the ECM wake-up signal and communication circuits. If testing confirms internal ECM damage, replace the Engine Control Module and complete immobiliser system matching, VIN writing, throttle self-learning, and system configuration parameter writing.
Real-World Cases
BYD DTC AI Analysis

Song Plus DM-i ECM data corruption causing limp mode

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Symptoms: While driving, the instrument cluster suddenly displayed "Check Powertrain", the engine stalled, and the vehicle entered limp mode with the ABS/ESC warning lights on. The scan tool retrieved U01000A (ECM Data Corrupted 6) and U01000D (ECM Communication Timeout). Diagnosis: ECM power supply and ground checked normal. CAN bus voltage was normal. However, the fault codes would not clear and consistently returned after 5–10 km of driving. Found the ECM had early software version V1.02 with a data validation defect. Fix: Reflashed the ECM to version V2.15. Cleared the faults and road-tested 50 km—no recurrence. Recommend also checking the seal on the large engine compartment wiring harness connector.
Original source ↗
BYD DTC AI Analysis

DM-i Series ECM Main Relay Fault Causing Communication Abnormality

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Symptoms: Vehicle wouldn't start after sitting overnight. Start button unresponsive, or dash displayed "Check Power System" with the warning light on. Some owners reported sudden power loss while driving. Diagnosis: Scanner read U0100 series codes (including U01000A). Checked ECM supply voltage: dropped from 12V to below 8V with ignition ON. ECM main relay in the engine compartment fuse box had severely burnt and blackened contacts; high internal resistance caused unstable power supply. Resolution: Replaced ECM main relay. Tested 12V battery health (SOH below 50%) and replaced the worn battery. Fault resolved.
BYD DTC AI Analysis

Qin Pro DM: Engine bay water ingress caused ECM data abnormality

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Symptoms: Vehicle fails to start after rain or washing; fault is intermittent and frequency increases with humidity. Scanner sometimes cannot access the ECM or reports U01000A data corruption. Diagnosis: Checked the engine bay harness and found the ECM connector seal aged and deformed, with visible moisture and green corrosion on the pins inside. This caused intermittent CAN signal shorts to ground and data frame errors. Resolution: Cleaned the ECM connector pins thoroughly with anhydrous alcohol and compressed air, replaced the waterproof seal, applied conductive paste, reassembled, and wrapped the harness with waterproof tape. Fault eliminated.
Original source ↗
BYD DTC AI Analysis

Sealion 6 DM-i hybrid system communication data anomaly

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Symptoms: Drove normally in EV mode. When switching to hybrid mode (HEV), the engine failed to start. The dash displayed a powertrain fault warning and the ESC warning light illuminated. Diagnosis: Retrieved DTCs U01000A and U0103 (lost communication with BMS). Checked wiring harnesses in the high-temperature areas of the engine bay. Found the CAN harness between the ECM and VCU had insulation damaged from heat aging, causing intermittent shorts and data frame errors. Also identified a protocol compatibility issue between the ECM and VCU software versions. Fix: Repaired the damaged wiring and added thermal protective sleeving. Reflashed the ECM and VCU to the latest software versions. Completed system configuration learning. Fault resolved.
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.