A distribution center reported that a Toyota 8FBMT25 hybrid electric forklift would randomly lose drive power and display a "Check Hybrid System" warning light. The machine would coast to a stop and then restart after sitting for 10 minutes. The lift functions continued to work during the drive failure.
The 8FBMT25 uses a hybrid system with a diesel engine and an electric drive motor. The technician connected the Toyota diagnostic laptop and retrieved a fault code for "Inverter Overtemperature" and "Motor Speed Sensor Signal Loss." However, the inverter temperature on the live data screen was only 45°C, ruling out actual overheating.
The technician inspected the inverter connections located under the battery compartment. The main 3-phase connector linking the inverter to the drive motor was covered in white corrosion and battery acid residue. The forklift had been operating in a battery charging area where acid fumes were present. The corrosion was creating high resistance across the speed sensor wires, causing the inverter to think the motor was overheating or running away, triggering a safety shutdown.
The technician cleaned the connector pins with a specialized contact cleaner and applied a dielectric grease to prevent future corrosion. The speed sensor connector was also checked and found to have a broken locking tab, causing it to vibrate loose. A new connector was crimped in place. After clearing the fault codes, the forklift was driven through a rigorous stress test in the charging area, and the drive power remained constant with no warning lights.
