AU
U01000D

U01000D is a BYD-specific subtype of ISO standard communication fault code U0100 (suffix 0D is a hexadecimal identifier) — Atto 3

Braking System

U01000D is a BYD-specific subtype of ISO standard communication fault code U0100 (suffix 0D is a hexadecimal identifier).

It indicates a failure to receive a valid data frame via the CAN network between the IPB (Intelligent Power Brake system) and the ECM (Engine Control Module) within a specific cycle (typically 100ms-500ms, depending on calibration).

This triggers the timeout counter to reach its threshold (6th timeout).

In the DM-i hybrid architecture, the IPB must retrieve real-time engine torque, engine speed, and brake energy regeneration request status from the ECM.

Communication interruption degrades the brake energy regeneration function, disables ESC coordinated control, and in severe cases, triggers Limp Home mode.

The basic hydraulic braking function remains available.

5
Cases Logged
5
Causes
Likely Causes — Atto 3
  • 1Intermittent open circuit, short circuit, or short to ground/power in the ECM or IPB CAN-H/CAN-L wiring, especially wiring harness sleeve damage in high-temperature areas of the engine compartment.
  • 2Abnormal ECM power supply circuit (including constant power B+ and ignition switch power IG1/IG2) or excessive ground circuit resistance (>1Ω), causing intermittent ECM restarts.
  • 3CAN bus termination resistance between the IPB and ECM deviates from specification (standard value 60Ω, allowable range 58-62Ω), or the branch line length exceeds 0.3m, causing signal reflection.
  • 4Hardware fault in the ECM internal transceiver or IPB gateway module, preventing response to Network Management (NM) messages.
  • 5Aftermarket equipment (such as a dash cam or inverter) connected to the CAN bus causing excessive bus load or signal interference.
What To Do
  • 1
    Use the VDS1000 or DiLink diagnostic tool to perform a 'Vehicle Scan', record the U01000D freeze frame data, and confirm the vehicle speed, SOC, and communication status bits when the fault occurred.
  • 2
    Inspect ECM connector BYD-121PIN (front left of the engine compartment) and the IPB connector (front of the engine compartment firewall). Verify no backed-out pins, oxidation, or signs of water ingress. Apply electronic contact protectant and reconnect.
  • 3
    Measure the resistance between pin 6 (CAN-H) and pin 14 (CAN-L) of the OBD diagnostic port: with the vehicle powered off, the resistance must be 60±2Ω. Measure the voltage to ground: CAN-H 2.6-2.8V, CAN-L 2.2-2.4V. Use an oscilloscope to check the waveform for distortion or bit errors.
  • 4
    Check ECM power supply: Measure pin A01 (constant power); voltage must be 12V±0.5V. Measure pin A02 (IGN power); voltage must be ≥12V with the ignition switch ON. Check resistance between ground pins A03/A04 and body ground; resistance must be <1Ω.
  • 5
    Perform the 'Communication Test': Disconnect the ECM connector and connect a terminal resistor simulator (120Ω) in parallel to the CAN line on the IPB side. If the fault code changes to U010087 (permanent loss), confirm an internal ECM fault. If it remains U01000D, check the IPB gateway and wiring harness.
  • 6
    After clearing the fault code, perform a road test: simulate regenerative braking at different vehicle speeds (0-60-120 km/h) and observe whether 'ECM_Torque_Request' and 'IPB_Recup_Torque' in the data stream update synchronously.
  • 7
    If testing confirms an ECM fault, perform 'Online Coding' to match the VIN and immobiliser key. For wiring harness issues, repair the harness, wrap it with waterproof tape (3M Scotch 33+), and secure it in the original clip position.
Real-World Cases
BYD DTC AI Analysis

Song PLUS DM-i: Intermittent full illumination of instrument panel and hard brake pedal

✓
Vehicle: 2021 Song PLUS DM-i 110km Flagship, 23,000 km. Symptoms: While driving at highway speeds, the dashboard suddenly displayed "Check Engine System" and "Check Brake System" warnings, the ESC light came on, and the brake pedal went hard but still had braking. Diagnosis: VDS read code U01000D (current fault) from the IPB system; the ECM had no communication. Technicians found fretting wear on pin 45 (CAN-H) of the 121-pin ECM connector—contact resistance spiked to 5 Ω under vibration. Repair: Replaced the ECM connector assembly (part number BYD-3724010), re-crimped the terminals, measured CAN bus resistance at 60 Ω, and road-tested 20 km with no recurrence.
Original source ↗
BYD DTC AI Analysis

Aftermarket dash cam installation caused CAN network failure on Tang DM-i

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Vehicle: 2022 Tang DM-i 252KM Premium. Symptoms: After the owner installed an aftermarket 360-degree surround-view camera, the vehicle frequently set DTCs U01000D and U010104 (lost communication with TCU) and failed to enter READY mode. Diagnosis: Removing the aftermarket equipment cleared the fault. Further inspection found the device tapped power from the OBD port and was spliced in parallel into the CAN bus without authorization. Repair: Removed the non-factory wiring harness, restored the original CAN bus topology, and re-grounded the shield at the BCM. Fault eliminated. Recommendation: Never connect aftermarket devices in parallel to the Powertrain CAN.
Original source ↗
BYD DTC AI Analysis

Qin PLUS DM-i ECM internal transceiver fault causing communication timeout

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Vehicle: 2021 BYD Qin PLUS DM-i 55KM Flagship, 41,000 km. Symptoms: Cold start normal; DTC U01000D triggers at operating temperature (coolant >90°C) with engine shake. Diagnosis: Oscilloscope captured CAN waveforms at the ECM; CAN-H amplitude dropped from 2.8V to 1.2V under high temperature. ECM internal CAN transceiver (TJA1043 chip) thermal stability failure. Repair: Replaced ECM assembly (PN BYD-3610000B), performed online programming and immobilizer matching, flashed IPB control logic with software version 20230815 to increase communication fault-tolerance delay.
Original source ↗
BYD DTC AI Analysis

Song Pro DM-i wiring harness chafes against body, causing intermittent open circuit

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Vehicle: 2022 Song Pro DM-i 110km, 18,000 km. Symptom: Intermittent U01000D on rough roads; normal on smooth surfaces. Diagnosis: Lifted vehicle and inspected chassis harness. Found ECM-to-IPB CAN harness chafing against metal burrs at firewall penetration. Insulation wore through, partially fracturing conductors (only 2 strands remained connected). Repair: Repaired harness using 0.5mm² twisted-pair shielded cable (20mm twist pitch). Installed rubber grommet (part number BYD-33316) at penetration point. Re-secured routing to maintain >50mm clearance from body.
BYD DTC AI Analysis

Seal DM-i IPB gateway module software bug caused false alarm.

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Vehicle: 2023 Seal DM-i 1.5L 121km, 500 km. Symptoms: No driving abnormalities, but instrument cluster reports U01000D after every fast charge; clears after 5 minutes of driving. Diagnosis: Data stream analysis showed high BMS load during fast charging occupied powertrain CAN bandwidth; IPB gateway priority configuration caused ECM message packet loss. Repair: Upgraded IPB control software to V2.3.1 (BYD internal TSB-2023-BR-09) and adjusted Network Management (NM) message transmission cycle from 20ms to 10ms. Fault eliminated.
Other Atto 3 Fault Codes
P0AA6Hybrid Battery Voltage System Isolation FaultB1108For 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.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.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.B173A1ADTC B173A1A indicates the right middle-row side airbag (typically located on the side of the right second-row seat or inside the C-pillar trim panel) igniter circuit resistance measures 0 Ω. In the Supplemental Restraint System (SRS), normal airbag igniter resistance ranges between 2.0 and 5.0 Ω. A resistance of 0 Ω indicates a short to ground or a short between circuit wires, preventing the Airbag Control Unit (ACU) from establishing a normal monitoring circuit. This safety-critical fault prevents the airbag from deploying during a collision, continuously illuminates the instrument panel SRS warning lamp, and may force the entire airbag system into fail-safe mode.
Common problems reported for Atto 3 →Atto 3 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.