The Sauer‑Danfoss S1X‑11 515604 is a mobile microcomputer controller designed for open‑loop and closed‑loop hydraulic and motor applications in off‑road machinery. Common failure points for this class of units include power supply degradation, board component burn‑outs (capacitors, diodes), and firmware corruption or communication link faults between the unit and hydraulic actuators. First‑check diagnostics: verify input voltage and ripple on the 24 VDC rail; inspect the PCB for visible damage or solder bridges; confirm that I/O signals to the actuator driver are present and within spec; review any error codes displayed on the unit’s indicator panel or transmitted via its communication interface.[oss-gpt-20b]