SUPPORT AS 3852310 - Caterpillar

Illustration 3 g03069717
Solenoid block (located under main control valve) (13) Heavy lift solenoid valve (14) Swing relief solenoid valveThe pilot circuit pressure is limited by pilot relief valve (23) .The oil delivery from pilot pump (26) performs the following main functions:
Provide pilot oil pressure to the pilot control valves for travel in order to perform machine operations.
Create pilot oil pressure in order to operate the control devices automatically.Note: Each pilot circuit performs one of the functions above.The pilot circuit is classified into the following circuits:
Pilot control valve circuits
Pilot Relief Valve
Travel Pressure Sensor Circuit
Straight travel valve circuit
Swing parking brake
Heavy lift
Swing Relief Solenoid Valve
Automatic travel speed changePilot Control Valve Circuits
Oil from pilot pump (26) flows through pilot line (25), pilot filter (24), and pilot line (22) to pilot manifold (19). When the hydraulic activation control lever is shifted to the UNLOCKED position, the machine ECM energizes the hydraulic activation solenoid valve (18). The pilot oil then shifts valve (18), allowing oil to flow through valve (18). The pilot oil now flows to pilot control valve (4), and main control valve (6) for implements, swing, and travel in order to perform machine operations. When the travel levers/pedals are moved, the pilot oil flows to main control valve (6) in order to control a travel function. Refer to Illustrations 4, 5 and Table 1 for the location of the pilot lines and machine operations.
Illustration 4 g03072259
(27) Pilot relief valve (28) Main relief valve
Illustration 5 g03072301
Table 1
Port     Control Valve     Machine Operation    
(29)     Left travel control valve     REVERSE LEFT TRAVEL    
(30)     Right travel control valve     REVERSE RIGHT TRAVEL    
(31)     Left travel control valve     FOWARD LEFT TRAVEL    
(32)     Right travel control valve     FOWARD RIGHT TRAVEL    For more information concerning the operation of the travel circuit, refer to Systems Operation, "Travel System".Pilot Relief Valve
The pilot relief valve is located on top of main control valve (6). The primary function of the pilot relief valve is to protect the pilot circuit if a failure was to occur. If an o-ring located on an IMV PHMV failed, the pilot relief valve protects the pilot circuit from the high-pressure supply oil circuit.Travel Pressure Sensor Circuit
When the travel controls are in the NEUTRAL position, travel pressure sensor (9) and travel pressure sensor (11) sense low pilot pressure. The machine ECM recognizes the low-pressure condition of the pressure sensors. The AEC system is activated in order to lower the engine rpm. If either travel control is moved from the NEUTRAL position, the pilot oil pressure increases and is sensed by travel pressure sensor (9) and travel pressure sensor (11). The machine ECM activates the AEC system in order to increase the engine rpm.Straight Travel Valve Circuit
When a swing operation and/or implement operation is performed during a travel operation, the machine ECM activates the straight travel PHMV. When the straight travel PHMV is energized, pilot oil to one side of the valve is directed to the return circuit,