AU
U01000D

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

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.

The U01000D fault code on the Seal U indicates a medium-severity CAN communication timeout between the Intelligent Power Brake system and the Engine Control Module. It can reduce brake energy regeneration and disable ESC coordinated control, while basic hydraulic braking remains available. Common causes include damaged CAN wiring in the engine bay or unstable ECM power/ground connections. The recommended fix is diagnosis and repair by an authorised dealer. Typical repair cost data is available.
5
Cases Logged
5
Causes
Likely Causes — Seal U
  • 1Intermittent open circuit, short circuit, or short to ground/power in the ECM or IPB CAN-H/CAN-L wiring, especially damaged wiring harness sleeves 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 IPB and ECM deviates from specification (standard value 60 Ω, allowable range 58-62 Ω), or branch line length exceeds 0.3 m, 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 causes 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 verify the vehicle speed, SOC, and communication status bits at the time of the fault.
  • 2
    Check ECM connector BYD-121PIN (located at the front left of the engine compartment) and the IPB connector (located in front of the engine compartment firewall). Verify there are no backed-out pins, oxidation, or signs of water ingress. Apply electrical contact protectant and reconnect.
  • 3
    Measure the resistance between pin 6 (CAN-H) and pin 14 (CAN-L) of the OBD diagnostic connector. With the ignition OFF, the resistance must be 60±2 Ω. Measure the voltage to ground: CAN-H 2.6-2.8 V, CAN-L 2.2-2.4 V. Use an oscilloscope to check the waveform for distortion or bit errors.
  • 4
    Check ECM power supply: Measure pin A01 (constant power); voltage should be 12V±0.5V. Measure pin A02 (IGN power); voltage should be ≥12V with the ignition switch ON. Check resistance between ground pins A03/A04 and body ground; resistance should 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), diagnose 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 (0-60-120km/h) and observe whether 'ECM_Torque_Request' and 'IPB_Recup_Torque' in the data stream update synchronously.
  • 7
    If diagnostics confirm an ECM fault, perform 'Online Coding' to match the VIN and immobilizer key. For wiring harness faults, wrap the repaired harness 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

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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 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.