Switches
Switch (All Wheel Drive) (AWD)
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| Illustration 1 | g00800675 |
Switch for the AWD mode | |
The AWD switch tells the all wheel drive ECM that the operator wants to select a mode of operation for the all wheel drive system.
The switch is a double-pole double-throw three-position rocker switch. The three positions represent the following modes:
- OFF
- AUTOMATIC
- MANUAL
The switch also has an internal lamp. The lamp connects to the lamp circuit of the machine.
When the switch is located in the OFF position, the terminals 2 and 3 and the terminals 5 and 4 will be closed.
When the switch is located in the AUTO position, the terminals 2 and 3 and the terminals 5 and 6 will be closed.
When the switch is located in the MANUAL position, the terminals 2 and 1 and the terminals 5 and 4 will be closed.
The ECM monitors the status of the switch. If invalid inputs are seen by the ECM, a diagnostic code will be active and the AWD will be disabled.
Sensors
Speed Sensor (Engine)
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| Illustration 2 | g00800750 |
Speed sensor for the engine RPM | |
The sensor continuously tells the all wheel drive ECM the engine speed. The ECM calculates the speed of the rear wheels by utilizing the engine speed and the transmission gear selection.
The engine speed sensor generates a frequency. The engine speed sensor generates a sine wave signal from passing gear teeth on the engine flywheel. The ECM measures the signal in order to determine the engine speed. The sensor generates 1 Hz per gear tooth.
The ECM monitors the engine speed sensor for abnormal frequencies. A diagnostic code will be set and the auto feature of the all wheel drive system will be disabled.
Speed Sensor (Ground)
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| Illustration 3 | g00800761 |
Speed sensor for the ground speed | |
The sensor continuously tells the all wheel drive ECM the true ground speed. The ECM calculates wheel slippage by finding the difference from the true ground speed and from the rear wheel speed. The wheel slippage is used during the AWD automatic operating mode.
The ground speed sensor is a radar sensor that measures the speed of the ground. The sensor produces a square wave signal that will vary as the speed changes. The frequency is generated at 27.4 Hz for every km/h (44.2 Hz for every mph).
The ECM monitors the ground speed sensor for abnormal frequencies. A diagnostic code will be set and the auto feature of the all wheel drive system will be disabled.
Position Sensor (Torque Lever)
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| Illustration 4 | g00800765 |
Position sensor for the torque control lever | |
The position sensor continuously tells the all wheel drive ECM the position of the torque control lever. The operator selects the position of the lever. The ECM utilizes the lever position in order to determine the output of the AWD pump.
The position sensor generates a pulse width modulated signal (PWM). The duty cycle varies in proportion to the position of the torque control lever. The ECM measures the duty cycle of the PWM signal in order to determine the position of the lever. A duty cycle of 0% corresponds to a lever position of 100%. A duty cycle of 100% corresponds to a lever position of 0%. The frequency of this signal is constant at 5000 Hz. The machine electrical system provides +battery voltage to the position sensor for operating power.
The ECM monitors the position sensor for abnormal duty cycles. A diagnostic code will be set and the all wheel drive system will be disabled.
Pressure Sensor (All Wheel Drive)
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| Illustration 5 | g00800762 |
Pressure sensor for the all wheel drive | |
The pump pressure sensor is located in front of the flushing valve.
The sensor continuously tells the all wheel drive ECM the hydraulic pressure in the AWD system. The ECM measures the frequency of the signal in order to determine the pump pressure. The ECM utilizes the pump pressure in order to determine the output of the AWD pump.
The pressure sensor generates a square wave signal which is in direct proportion to the pressure. A pressure of 0 (0) corresponds to a frequency of 200 Hz. A 35 kPa (5.0 psi) increases the frequency by 1.0 Hz. The machine electrical system provides +battery voltage to the pressure sensor for operating power.
The ECM monitors the pressure sensor for abnormal frequencies. A diagnostic code will be set and the all wheel drive system will be disabled.