ELECTRICAL SYSTEM CONTINUED
Blade Float Mode
The dozer has a pilot controlled bulldozer attachment system that has an electromagnet installed under the front of
the blade control handle. This magnet is energized at +battery voltage by the ECM at all times unless the key
switch is in the OFF position or the hydraulic lockout switch is in the LOCKED position. When the operator moves
the blade control handle to the full forward position, the electromagnet will hold the blade in this position until the
operator pulls the handle back. When the handle is in the full forward position, maximum pilot pressure will be
applied to the main valve in order to shift the spool to float position.
This will result in the pump port being blocked and both ends of the lift cylinders are ported to the tank. The blade
control handle can be returned to the center position. The ECM will keep the blade float active until another "Y"
axis (forward or rearward) handle movement is detected.
Electrical Input Components
The machine has several different types of devices that provide input data to the ECM. The ECM receives machine
status information from the input devices and determines the correct output action that is needed in order to control
machine operations based on memory and software parameters. The machine utilizes the following types of
inputs: switch type and sensor type.
Switches provide signals to the switch inputs of the ECM. The possible outputs of a switch are listed: an open
signal, a grounded signal, and +battery signal.
Sensors provide an electrical signal to the ECM that constantly changes. The sensor input to the ECM can be one
of several different types of electrical signals such as switch to +battery signals, switch to ground signals, analog
pulse width modulated (PWM) signals, and frequency input signals.
The ECM monitors the circuits of the input components. If the ECM determines that an abnormal condition exists in
one of the circuits, the ECM will log a diagnostic code for the involved component.
Figure 5. Inputs to the Powertrain ECM.