Sevcontrol MOS90 531/40056 is a DC traction and pump controller that integrates Mosfet power stages with a microprocessor for variable speed drive applications such as pallet trucks, reach‑in forklifts, and low‑capacity vehicles. Common failure modes on this unit include burned or tripped MOSFETs (visible as scorch marks or abnormal heat), regulator IC failures leading to erratic current regulation, and loss of communication between the controller and external I/O modules due to damaged UART/RS‑232 lines. First‑check diagnostics: verify that the 48 V DC supply is within spec and stable; inspect all power‑stage MOSFETs for overheating or physical damage; review any fault codes displayed on the LCD or via the serial interface, and confirm proper grounding and I/O wiring continuity before proceeding to deeper module testing.[oss-gpt-20b]