How to resolve the restricted function issue in BYD Song EV?
4 Answers
During an actual vehicle test, after starting the vehicle, the dashboard displayed an "EV function restricted" fault, making it impossible to switch to EV mode. The fault was confirmed, and the electronic fan was operating at high speed. By checking the data stream, it was found that the IPM radiator temperature was 35 degrees, while the motor temperature was 155 degrees, indicating an excessive (abnormal) temperature difference. Analysis suggests a fault in the drive motor cooling system.
A couple of days ago, I worked on a Song EV that also displayed a 'function restricted' warning. The technician used a computer to read the fault code, which showed an excessive battery voltage difference. In this case, there's an 80% chance the battery module is faulty. The 4S shop will disassemble the battery pack for balance calibration or replace the faulty module. Owners should never try to fix this themselves, especially avoid randomly unplugging high-voltage connectors! My advice is to pull over immediately if you see this warning on the road, try restarting, and if that doesn't work, call for a tow truck. In daily use, avoid leaving the car parked with a low battery for extended periods, and stop using fast charging immediately if the gun abnormally disconnects. These details can help reduce the battery failure rate.
Last rainy season, I encountered a sudden speed limit of 60 km/h while driving my Song EV, with a yellow warning light for function restriction popping up on the dashboard. Later, inspection revealed that the brake booster sensor was waterlogged, and replacing the part solved the issue. Such electronic failures are quite common; sometimes even high-pressure car wash jets aimed at the wheel hubs can trigger them. A temporary fix is to completely power off the system for 10 minutes to allow it to reboot, though this is only a stopgap measure. I make it a habit to keep an OBD port cover in the glove compartment, covering it during rainy days to prevent water ingress.
Don't panic when encountering functional limitations, first confirm the specific warning message. Energy recovery limitations may be due to temperature issues - turning the AC to maximum heat for an hour often resolves it automatically. Power system limitations usually require checking the electronic control unit. Last time I helped a fellow car owner diagnose hidden codes by connecting their phone to the vehicle system, we discovered it was drive motor overtemperature protection. For coolant circulation system issues like this, DIY solutions involve checking the cooling fan and coolant level, but those with limited mechanical skills should contact after-sales service directly for safest resolution.
