The body hoist system has two modes that will not allow the Power Train/Chassis Electronic Control Module (ECM) to follow the requests of the operator.
The body hoist system will be forced into hold under any of the following conditions.
- After power is applied to the ECM, the body hoist system will be forced into hold during the first two seconds.
- After the engine starts, the body hoist system will be forced into hold for the first two seconds.
- After the start relay magnetic switch has been energized, the body hoist system will be forced into hold for the first two seconds.
- The body hoist system will be forced into hold if the ECM records an active fault with the hoist lever.
- The body hoist system does not respond when any combination of faults with the solenoids has occurred and the body hoist system fails to respond to any requests from the operator.
Note: This is an example. If the solenoid that raises the body is shorted to the +battery, then the ECM will activate the solenoid that is used to lower the body. This is done in order to keep the body from moving. The override will be activated in order to prevent the body from continuing to move after the fault is removed. When the solenoid has an open circuit condition, the ECM will activate the override.
- 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 raised 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".