BYD Song PLUS EV Charge-Distribution Assembly Structure and Fault Repair Guide

Fault Background

The charge-distribution assembly of the Song PLUS EV is mounted in the upper front compartment. It is a high-voltage hub that combines "charging" and "distribution": AC charging and DC charging enter from two charge ports, and the assembly distributes high voltage to the motor controller, A/C compressor, and A/C PTC heater, while also outputting low voltage externally. The cover of the housing also contains four load fuses. Typical symptoms of failure are "cannot charge" or "one load circuit has no power." There are two repair routes: replace the assembly if external interfaces and the traction battery are normal; open the cover for repair if only a load fuse is blown—but before opening the cover, you must confirm that the DC bus voltage is zero. This article compiles a field guide covering layout, interfaces, diagnostic procedures, replacement, and fuse repair.

Layout and Structure

• Location: The charge-distribution assembly is in the upper front compartment; the DC charging socket sub-assembly is on the left rear side panel, and the AC charging socket sub-assembly is on the right rear side panel; the high-voltage distribution wiring harness runs along the lower body to connect the charge-distribution assembly and the traction battery.
• Main interfaces of the assembly:

• Main pins of the low-voltage connector: Pin 6 OBC-CMC charging connection signal to battery pack 33pin-30; CONTROL-JCQ+ DC charging control signal to battery pack 33pin-24.

Fault Diagnosis Procedure

1. Check the 12V battery: Standard voltage 11~14V; if below 11V, charge or replace before continuing.
2. Refer to the fault diagnosis table: If the symptom is listed, follow the entry; if not, follow the general troubleshooting procedure; after adjustment, repair, or replacement, confirm with a test.

Cannot AC charge troubleshooting sequence: Check the external interface of the charge-distribution assembly and the low-voltage connector of the AC charging socket → reconnect → test if the vehicle can drive in OK mode → check the battery management system (BMS) and motor controller → check if charging works in OK mode → check low-voltage distribution and gateway → replace the charge-distribution assembly.

DC bus voltage abnormal troubleshooting sequence: In ON mode, use VDS to read the traction battery voltage from the BMS → if abnormal, check the traction battery; if normal, in OK mode use VDS to read the DC bus voltage → if abnormal, check the battery pack and high-voltage lines → if still unresolved, replace the charge-distribution assembly.

Cannot DC charge (VDM fault) troubleshooting sequence: First replace the charging station and test if charging works → if not, check the BMS → troubleshoot according to the VDM fault code table. Typical example: DC positive/negative contactor welded (e.g., P1CA800): clear the DTC, replace the charging station, test again, read and record the fault code reported by the station; if no station is available, clear the code and charge again; if the same fault recurs, replace the charge-distribution assembly.

Insulation faults: Check all high-voltage electrical components, high-voltage lines, and the traction battery; use an insulation resistance tester or multimeter to isolate the insulation fault.

Replacing the Charge-Distribution Assembly

1. Turn the vehicle off to OFF mode, disconnect the low-voltage battery negative terminal;
2. Disconnect the connector between the charge-distribution assembly and the traction battery;
3. Use water pump pliers to disconnect the inlet hose, outlet hose, and vent hose;
4. Manually disconnect the A/C PTC connector, A/C compressor connector, AC charging input connector, in-vehicle discharge connector, and low-voltage harness connector (note the connector has a secondary locking mechanism);
5. Use a 13mm socket to remove the low-voltage positive cable and 2 ground cables, and remove the harness clips;
6. Use a special tool to remove the 23 bolts of the cover (2 internal Torx bolts and 21 external hex bolts); after removing the cover, prevent foreign objects or water from falling into the housing;
7. After opening the cover, first use a multimeter to measure the DC bus voltage and confirm it is 0 before proceeding;
8. Remove the M6 bolts (10 total) for the busbar lugs of the motor controller busbar and DC charging harness;
9. Use a 13mm socket to remove the 4 M8 bolts of the mounting feet of the charge-distribution assembly;
10. Remove the faulty assembly, install the new one in reverse order of removal, using the same tools.

Repairing the Charge-Distribution Assembly (Load Fuses)

The cover of the charge-distribution assembly contains four load fuses: DC charging fuse, PTC fuse, compressor fuse, and DC/OBC fuse. If one load circuit has no power, follow this procedure:

1. Use a special tool to remove the 23 cover bolts (2 internal Torx + 21 external hex), preventing foreign objects or water from entering the housing;
2. After opening the cover, use a multimeter to check the continuity of the corresponding load fuse;
3. If the fuse is blown, replace it with the same specification, and install the cover with the specified torque (M5 bolts 2.8±0.3N·m).

Safety Warnings

• This article is for technical reference only; high-voltage repairs must be performed by certified personnel following OEM specifications. Unfamiliar readers are strictly prohibited from performing operations themselves.
• Strictly follow the power-off sequence: OFF mode → disconnect low-voltage battery negative → disconnect traction battery connector; before opening the cover, confirm with a multimeter that the DC bus voltage is 0.
• When disconnecting high-voltage connectors, pay attention to the secondary locking mechanism to prevent damage; after opening the cover, prevent foreign objects or water from entering the housing.
• Fuse replacement must use the same specification; do not use copper wire or other substitutes to short-circuit the fuse.

Repair Insights

The charge-distribution assembly combines the "charging inlet" and "distribution outlet" into one node, so its troubleshooting logic is well-suited to the "watershed method": first determine whether the fault is on the "input" or "output" side—if AC charging fails, follow the sequence "interface connection → can it drive → battery/motor control → low-voltage distribution/gateway → replace assembly" to narrow down step by step; if DC charging fails, first replace the charging station to rule out external factors, then check the BMS. The only case that truly requires opening the cover is: one load circuit (PTC/compressor/DC-OBC/DC charging) has no power alone, then first check fuse continuity—the four fuses downgrade the major operation of "replacing the assembly" to a minor repair of "replacing the fuse." Also, keep two numbers in mind: the bus voltage must be zero before opening the cover, and the cover M5 bolts are only 2.8±0.3N·m—if over-torqued, the threads will strip, ruining the seal and tamper-proofing.

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【This article is for reference only】