Komatsu Fault Code
Free · no signupSPN 520201 FMI 05
Boom Up Drift / Slow Raise Cycle
System
Hydraulics
Symptom
Boom Up Drift / Slow Raise Cycle
Diagnosis & fix steps
LOGIC: Boom 1 Regeneration Cancel Solenoid Circuit Open.
ACTION: Inspect the regeneration cut solenoid on the main five-spool valve block. Measure coil resistance (~24Ω) and check the harness connector for broken terminal locking tabs.
Red Seal field insights
Cycle Velocity: Disabling regeneration during heavy craning operations ensures positive hydraulic holding; an open circuit keeps regeneration active, reducing lifting breakout force.
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