Fault Phenomenon: SANY SY5410THB speed is normal when cold. During high-speed driving (operating temperature), vehicle speed is limited, engine RPM cannot increase, and speed is eventually capped.

Troubleshooting Process:
– Checked vehicle speed sensor: sensor installed securely, signal normal.
– Checked accelerator pedal: pedal travel normal, no sticking.
– Checked transmission oil temperature: temperature normal, not over limit.
– Measured vehicle speed signal frequency at operating temperature: found abnormal frequency fluctuation.

Root Cause: Poor thermal stability of internal components in the vehicle speed sensor leads to signal distortion.

Required Parts: Vehicle speed sensor.