Fault Phenomenon: XCMG TY220 dozer transmission can only engage low gear, cannot engage high gear.

Troubleshooting Process:
– Checked speed sensor: sensor signal lost.
– Checked shift solenoid valve: high gear solenoid valve coil burnt.
– Checked oil pressure: insufficient high gear clutch pressure.
– Checked control computer: TCM fault code causing limitation.

Root Cause: The high gear shift solenoid valve coil is burnt, preventing the spool from moving and the high gear clutch from engaging.

Required Parts: Transmission shift solenoid valve assembly.