Fault Phenomenon: Schwing S425 idles smoothly when cold. After reaching operating temperature (water temp 90℃), the engine idles rough, black smoke comes from the exhaust, and eventually stalls.

Troubleshooting Process:
– Checked air filter: unobstructed, no blockage.
– Checked injector atomization: bench test normal, no dripping.
– Checked crankshaft position sensor wiring: no damage, connections secure.
– Measured crankshaft position signal at operating temperature: found signal amplitude attenuates at high temperature.

Root Cause: Poor thermal stability of the crankshaft position sensor magnetic core leads to signal loss.

Required Parts: Crankshaft position sensor.