BYD Yuan PLUS Integrated Smart Front Drive Assembly Parameters, Disassembly, and VDS Calibration Guide

Fault Background

The Yuan PLUS front drive system is an "eight-in-one" integrated smart front drive assembly: the powertrain domain controller, drive motor, and single-speed reduction gearbox are integrated into one unit mounted on the subframe. The repair rules for this assembly are completely different from traditional vehicles—the powertrain domain controller is not allowed to be opened and repaired on-site; it must be returned to the factory. Moreover, after replacing the powertrain domain controller or drive motor individually, four software procedures must be completed on VDS: zero position calibration, anti-theft matching, inclination calibration, and cruise configuration calibration. Missing any one may result in the OK light not illuminating or abnormal calibration status. This article compiles technical parameters, disassembly/assembly and air-tightness testing, diagnostic procedures, and the four calibrations into an on-site guide.

Technical Parameters and Assembly Composition

• Bus voltage reference: Normal DC bus positive-to-negative voltage of the powertrain domain controller is 200~500V; rated voltage per vehicle configuration is 332.8V (SC2EE) / 403.2V (SC2EF).
• Stator lead wires: Copper bar terminals from left to right phase sequence is U, V, W.
• Main low-voltage connector pins: Accelerator depth 1 power supply / accelerator depth 2 power ground / accelerator depth 1 power ground connect to accelerator pedal pins 3/6/5 respectively; BASU power ground (contactor power supply) connects to the traction battery.

Disassembly/Assembly and Air-Tightness Testing

Assembly Disassembly: First remove the assembly from the subframe mounting points; when disassembling the casing, use a 10# socket wrench to remove bolts in order 1~7, then remove 1 fixing nut and 2/3/4 fixing bolts in order to remove the upper casing cover, and finally remove the left and right casing parts (plastic clips + metal nuts).

Powertrain Domain Controller Disassembly:

1. Remove the 6 M10 bolts fixing the controller housing to the drive motor and gearbox front housing, and separate the controller;
2. Remove the 14 M5 bolts of the drive motor end cover, then remove the three-phase wire bolts connecting the drive motor controller to the drive motor, and unplug the resolver and temperature sensor connector;
3. Protect the water inlet during disassembly to avoid hard contact with the motor; the removed powertrain domain controller is returned to the factory for disassembly and repair.

Return-to-Factory Rule: If it is determined that the gearbox assembly or drive motor assembly has issues requiring factory return, after removing the integrated smart front drive assembly, return both the gearbox and drive motor to the factory for disassembly and repair—do not disassemble these two parts on-site.

Air-Tightness Testing (after new powertrain domain controller assembly):

Diagnostic Procedure

1. Check battery: Standard voltage 9~16V; if below 9V, charge or replace before continuing.
2. Read codes: Connect diagnostic equipment for terminal diagnosis, read and record all module DTCs.
3. Re-read codes: Clear all DTCs, turn OFF, wait 3 minutes, then turn ON again, read and record again.
4. Refer to fault diagnosis table: If the symptom is in the table, handle per item; if not, check the DC bus—with ignition ON, check whether high voltage is applied between bus positive and negative, normal 200~500V; if abnormal, check the traction battery or DC bus.
5. After repairing or replacing the powertrain domain controller, test to confirm.

Four VDS Calibrations (Mandatory After Part Replacement)

I. Motor Zero Position Calibration (after replacing the powertrain domain controller or drive motor assembly individually):

1. Record the motor zero position barcode on the motor (the last four digits of the barcode are the zero position value);
2. With the vehicle ON, P position, stationary, connect VDS: Vehicle Diagnostic System → Passenger Vehicles → EV Series → Select SC2E model (SC2E-2021) → ECU Modules → Enter Scan;
3. After scanning, select "Front Drive Motor Controller" to enter the diagnostic page;
4. Select "Live Data" → All Data Streams → go to page 3, view and record the original motor zero position value;
5. Stop the data stream, return to the front motor controller page, click "Motor Zero Position Calibration";
6. Enter the zero position barcode of the installed motor (note case sensitivity): if the barcode is correct, it shows "Operation Successful"; if incorrect, it shows "Negative Response", and the zero position value changes to the default 07BC;
7. After powering off and restarting the vehicle, repeat the data stream reading to confirm the latest zero position value matches the motor barcode zero position value.

Notes: After zero position calibration, you must power off and restart to read the calibrated zero position value; if multiple correct entries still show "Negative Response", record the motor and controller barcodes and the vehicle VIN and report to the manufacturer.

II. VCU Anti-Theft Matching (after replacing the powertrain domain controller):

1. Before removing the old powertrain domain controller, use VDS to perform "Special Diagnostic Functions → Motor Controller Password Clear" (ensure the key is near the in-car detection antenna; if the controller is damaged and cannot execute, skip the password clear step);
2. Remove and install the new powertrain domain controller;
3. Repeat "Special Diagnostic Functions → Motor Controller Programming" to complete programming;
4. Power off and on again; the vehicle should illuminate the OK light normally.

III. Powertrain Domain Controller Inclination Calibration: Park the vehicle on a level surface → ECU module scan → select "Powertrain Domain Controller" → execute "Inclination Calibration" → read the inclination calibration status via live data; it shows "Calibrated" for success.

IV. Cruise Configuration Calibration: ON position → vehicle module scan → Powertrain Domain Controller → "Actuator Test" → "Cruise Configuration Calibration", select the corresponding option according to the vehicle's current configuration (cruise control or adaptive cruise control), follow VDS prompts to complete → power off and on again.

Typical DTCs and Handling Points

Safety Warnings

• This article is for technical reference; high-voltage repairs must be performed by certified personnel per OEM specifications. Readers unfamiliar with the procedures are strictly prohibited from operating on their own.
• The powertrain domain controller support capacitor has active discharge (<3s) and passive discharge (<2min) protection; after power-off, still confirm the DC bus voltage is within a safe range before working.
• The controller, motor, and gearbox are not to be opened for repair on-site after separation; after controller replacement, the four VDS calibrations (zero position/anti-theft/inclination/cruise) are all mandatory; if calibration fails, report to the manufacturer per the manual.
• Assemblies that fail air-tightness testing are prohibited from installation; protect the water inlet and three-phase copper bars during disassembly/assembly to prevent impact damage.

Maintenance Insights

The repair logic for the Yuan PLUS front drive assembly can be summarized as "hardware returns to factory, software stays at the shop": at the hardware level, the controller is not repaired but replaced, and the motor and gearbox are returned to the factory as a unit; the shop only performs disassembly/assembly and air-tightness testing (two leakage red lines: housing 50Pa, water jacket 200Pa). At the software level, part replacement is just the beginning—zero position calibration prevents "motor rotating in wrong direction", anti-theft matching prevents "new controller not recognizing the key", and inclination and cruise calibrations complete the vehicle attitude and driver assistance configuration. The two most practical on-site details: first, the last four digits of the zero position barcode are the zero position value; after calibration, you must power off and restart, then read back the data stream to verify; if the default value 07BC appears, it means calibration did not take effect. Second, for communication DTCs, check the other module first, then the gateway, and only last consider replacing the powertrain domain controller—keep the "replacement right" last to avoid detours.

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【This article is for reference only】