993K Wheel Loader Electrohydraulic System Caterpillar

Illustration 1	g01458564

All of the input components that supply inputs to the ECM are a part of one of the following groups: sensor inputs and switch inputs. The Implement ECM monitors most of the circuits of the input components for diagnostics. If the ECM determines that an abnormal condition exists in one of the circuits, the ECM will log a diagnostic code or an event code for the involved component.

Sensors

Sensors provide an electrical signal to the ECM that constantly changes.

Position Sensor for the Lift/Tilt Control Lever

Illustration 2	g01337660

The sensor is designed to tell the ECM the position of the lever. The live lever has three ranges: raise, hold and lower. The operator selects the range and the sensor sends the signal to the ECM. The sensor generates a PWM signal continuously. The duty cycle of the signal varies in proportion to the position of the lever. The ECM receives the PWM signal. Then, the ECM measures the duty cycle in order to determine the position of the lever.

Switches

Switch (Hydraulic Lockout)

Illustration 3	g01470411

The hydraulic lockout switch is used to inform the ECM that the operator is intending to lock the hydraulics for the implements. The switch is a rocker switch. The switch is located on the right hand console in the cab.

The common switch contact 5 for the input pole is connected to frame ground. The normally closed contact is contact 4. The normally open contact is contact 6. Contact 4 and contact 6 provide two inputs to the ECM.

When the switch is in the LOCKED position, the ECM input at switch contact 4 is switched to ground. When the switch is in the UNLOCKED position, the ECM input at contact 6 is switched to ground.

When the switch is in the LOCKED position, the ECM outputs a power signal in order to energize the hydraulic lockout solenoid. The solenoid is located on the hydraulic relief valve. When the solenoid is energized, pilot pressure for the implement system will be blocked.

Note: Two circuits for each switch are used for diagnostic purposes. The circuits are Normally Closed and Normally Open. If the two circuits are in the same state, a circuit failure is present and the ECM will activate a diagnostic code for the switch.

Kickout Set Switch

Illustration 4	g01470654
Kickout Set Switch

The kickout set switch is a momentary rocker switch that is located in the operator compartment. The kickout set switch is used by the operator to set the kickout positions for the lift lower, the lift raise, and the bucket tilt. When the switch is pushed, the ECM records the current position of the lift arm. The ECM uses the recorded position for the lift kickout position or the lower kickout position. If the upper position of the kickout set switch is depressed and the lift arm is above midway, the kickout will be set for raising the lift arm. If the upper position of the kickout set switch is depressed and the lift arm is midway below halfway, the lower kickout will be set. If the lower position of the kickout set switch is depressed the rotation of the tiltback will be set.

The switch has two input connections to the ECM. Switch terminal (1) connects to location (J1-40) . Switch terminal (3) connects to location (J1-35) . Both of these connections are normally open. When the switch is in the LIFT position, switch terminal (3) is closed to ground. Switch terminal (1) is open or floating. When the switch is in the TILT position, switch terminal (1) is closed to ground. Switch terminal (3) is open or floating.