Hitachi ZAXIS 120-6 class Operator's Manual page 472

Drive Function
Problem
One or both side tracks are inoperable. Damaged center joint
Does not travel smoothly.
Travel speed does not change.
TROUBLESHOOTING
Cause
Incompletely released parking brake
Broken travel motor
Faulty pilot valve
Faulty pilot circuit line
Overly tensioned or slackened crawler sag
Lack of lubricant in front idler and/or roller
Deformed track frame
Embedded foreign matter such as rock
fragments
Dragged parking brake
Faulty travel mode switch.
Faulty pressure sensor.
Pump 1 and 2 delivery pressure sensors
Pumps 1, 2 control pressure sensors
Poor contact in connectors
Damaged wire harness
Faulty controller (MC)
Faulty solenoid valve
Faulty motor
11-6
* Repair or replace
* Repair or replace
* Repair or replace
* Replace
* Repair or replace
Adjust
Refill
* Repair or replace
Remove
* Repair
* Replace
* Replace
* Repair or replace
* Repair
* Replace
* Repair or replace
* Repair or replace
Items with * mark: Consult your authorized dealer.
Solution