COVER GP-VALVE MECHANISM 2951000 - Caterpillar

Dead Engine Lower Function For The AD55 Machine
The body hoist system will be forced into hold if the engine is not running and the operator is not trying to lower the body.If none of the above conditions are true, the override will stay active until the hoist lever is placed in the HOLD position or the hoist lever moves through the HOLD position.If the engine is dead and the body is in the up position, the operator must have a way to lower the body.If the operator attempts to lower the body with a dead engine, the override will be cancelled. The ECM would not normally allow the body to be lowered with a dead engine.The following conditions must be met in order to clear the override.
The hoist lever must be in the HOLD position for a moment. Next, the hoist lever must be in the RAISE position for 15 seconds.
The start relay magnetic switch must be off.
The engine status must be off or the engine status must be unknown for at least 15 seconds.The operator may then place the lever in the FLOAT position. The lower solenoid for the hoist will be energized when the lever is in the FLOAT position. However, the valve that activates the hoist will not move until pilot pressure oil is available.Pilot pressure oil is attained from the brake release electric drive pump.Reference: For more information on the dead engine lowering function, refer to Operation and Maintenance Manual, "Equipment Lowering with Engine Stopped" for the machine that is being serviced.