| |
| Illustration 1 | g02473276 |
The electronic control of the Implement System will utilize different types of devices that provide input data to the Implement ECM. The ECM uses the input data to determine the correct output responses needed to control the implement functions based on memory and software parameters. All of the system input components that supply inputs to the ECM fall into one of the following groups:
- sensor type inputs
- switch type inputs
Note: The ECM monitors most of the circuits of the input components for diagnostics. When the ECM finds an abnormal condition with a circuit, the ECM will log a diagnostic code, or an event code, for that circuit.
Sensors provide an electrical signal to the ECM that constantly changes. The sensor input to an ECM can be one of the several types of electrical signals. The types of sensor signals are:
- Pulse width modulated (pwm) sensors
- Voltage input sensors
- Resistive input sensors
- Frequency inputs
Pulse Width Modulated (PWM) Sensors
When powered up, these types of sensors continuously send a Pulse Width Modulated (PWM) square wave signal to the ECM. The voltage of the signal ranges between 0.0 VDC and 5.0 VDC. The ECM monitors the voltage and the duty cycle of the signal. The PWM duty cycle is the percentage of time that the signal is high as compared to the time interval of one complete square wave cycle (hertz). The voltage of the signal corresponds to the duty cycle of the signal. A higher duty cycle results in a higher signal voltage.
The operating frequency of most PWM position sensors is approximately 500 ± 80 Hz. However, some PWM sensors operate at a frequency of approximately 5000 Hz.
An ECM will monitor the duty cycle, the voltage, and the frequency of the PWM signal. The voltage of the signal is used by the ECM as a status indicator for the sensor signal. The measurement of the signal duty cycle using a multimeter is used by the technician to determine the signal status.
Position sensors are the most commonly used type of PWM sensor. Any movement on the axis that is attached to the sensor will change the duty cycle and the voltage of the sensor output signal. The signal frequency can also change slightly, but the frequency change should not be great. The duty cycle of the PWM sensor signal changes according to the direction and amount of movement on the axis.
When an axis is moved, the ECM will interpret a specific duty cycle or voltage as a specific axis position. The ECM will determine the position based on the detected travel limits of the axis and the PWM duty cycle for those limits. The ECM can determine the axis limits by a manual calibration procedure that is performed by an operator. The ECM can also determine the axis limits by an automatic calibration procedure, performed by the ECM at machine start-up.
ECMs recognize as valid duty cycle signal percentages that are 10 to 90 (± 5) percent, at the extreme ends of axis movement. A joystick, pedal, or actuator that is in the center or neutral position results in a duty cycle signal approximately 50 (± 5) percent.
Internal pull up voltages are present at all PWM input circuits in the ECM. When a voltage signal is interrupted due to an open circuit or a poor connection, the signal circuit is pulled high. The ECM then activates an FMI 03, or "Voltage Above Normal" diagnostic code. The ECM will also activate an FMI 03 if the power supply to the sensor is interrupted,
Voltage input (active analog) type sensors provide a voltage input signals to the ECM that generally range between 0.0 VDC to 5.0 VDC. Active analog sensors are used for measuring pressure. The ECM will associate a specific voltage to a specific value for the medium that is being measured.
Most active analog sensors are powered by the ECM 5.0 VDC power supply and return circuits.
An internal pull up voltage is present at all analog input contacts on the ECM. If the voltage signal is interrupted due to an open circuit or poor connections or if the power supply to the sensor is interrupted, the signal circuit will be pulled high and the ECM will activate a "voltage above normal diagnostic" code.
Passive analog type sensors provide a resistive input signal to the ECM. The ECM also monitors the voltage of the circuit.
This type of sensor is used for temperature sensors. The ECM will associate a specific circuit resistance to a specific temperature value for the medium that is being measured
Most passive analog sensors are powered by the ECM 5.0 VDC power supply and return circuits.
An internal pull up voltage is present at all analog input contacts on the ECM. If the voltage signal is interrupted due to an open circuit or poor connections or if the power supply to the sensor is interrupted, the signal circuit will be pulled high and the ECM will activate a "voltage above normal diagnostic" code.
Speed sensors provide a frequency input signal to the ECM. Most of the speed sensors that are used on late model machines are "fixed mount" type speed sensors. No adjustment of the sensor is required once the sensor is installed.
A magnetic coil in the sensor creates a square wave voltage signal. That happens every time that a ferrous metal object, generally a gear tooth, passes under the sender tip. The ECM counts the number of square wave signals generated by the sensor to calculate a frequency. The ECM then uses that frequency to determine the speed of the gear being monitored.
Switches provide input signals to the ECM. As switch contacts change positions, either an open, a ground, or a voltage, is detected on the ECM input circuit.
Switch to Ground / Voltage Inputs
Switches will provide one of the following types of input signals to the ECM:
- An open signal
- A ground signal
- A voltage signal
The contacts of a switch have two contact states. The switch contacts are open or the switch contacts are closed.
- When switch contacts are open, no signal is provided to the corresponding input of the ECM. The "no signal" condition is also referred to as floating.
- When switch contacts are closed, either a ground signal or voltage signal is passed through the switch contacts to the corresponding input of the ECM.
Switch to ground type input circuits have an internal ECM "pull up voltage" that is present at the ECM contacts. An above normal voltage is internally connected to the ECM input circuit through a resistor. This condition allows the ECM to detect a problem in the switch circuit. During normal operation, the switch signal will hold the circuit low. However, circuit conditions such as a disconnection or an open circuit allow the circuit to be pulled high by the ECM pull up voltage. This condition will result in an above normal voltage condition at the ECM contact. If this condition occurs when the ECM is expecting the circuit to be low, the ECM will activate a diagnostic code for the circuit.
Switch to battery type input circuits have an internal ECM "pull down voltage" that is present at the ECM contacts. A below normal voltage is internally connected to the ECM input circuit through a resister. This condition allows the ECM to detect a problem in the switch circuit. The circuit will be held high when the switch contacts are closed to a system voltage source. If the circuit is open or has a bad connection, the pull down voltage will pull the circuit low. If this condition occurs when the ECM is expecting the circuit to be high, the ECM will activate a diagnostic code for the circuit.
Many switches often provide two inputs to the ECM. Generally, the two inputs are switch to ground type inputs. In each switch position, one of the inputs will be grounded and the other input will be floating. When the ECM determines that both of the inputs are grounded, the ECM will activate a diagnostic code for the switch. The ECM will also activate a diagnostic code for the switch if both of the inputs are floating high at the same time.
Blade Control Handle Position Sensors
| |
| Illustration 2 | g02470216 |
|
Blade control handle | |
| |
| Illustration 3 | g01974673 |
|
(1) Mode switch
(2) Switch (Increment) (3) Switch (Decrement) (4) Position sensor assembly for the blade control base (5) Blade control lever | |
The blade control lever is used to control the movement of the blade. When the lever is moved, the PWM sensors in the base of the lever communicate the movement of the lever to the Implement ECM. The sensors change the duty cycle of the PWM output to the Implement ECM according to the movement of the control handle. The Implement ECM will use this information to control the hydraulics to move the blade into the position that is commanded by the signal. The frequency of the PWM signal is constant at 500 Hz. The machine electrical system provides +battery voltage to the sensor for operating power. The center position of the handle is the HOLD position. Move the handle to the left to tilt the blade to the left. Move the handle to the right to tilt the blade to the right. Move the handle forward to lower the blade. Move the handle rearward to raise the blade. The sensor may be calibrated with Caterpillar Electronic Technician (ET). For more information, refer to Testing and Adjusting, "Calibration".
Position Sensor for Blade Tilt
Blade tilt is controlled by the position sensor that is located along the X-axis of the base of the blade control handle. When the handle moves along the X-axis, the Implement ECM receives a PWM duty cycle change from this sensor signal. The Implement ECM will process this signal to create an output to the solenoid for blade tilt. The duty cycle of the signal will vary in proportion to the position of the blade control handle.
Blade Raise and Lower Position Sensor
Raising and lowering the blade is controlled by the position sensor located along the Y-axis of the blade control handle base. The Implement ECM receive a change in the duty cycle of the PWM signal from this sensor when the handle is moved along the Y-axis. The Implement ECM will process this signal to provide an output to the blade raise or the blade lower solenoid. The solenoid will move the blade to the position that is commanded by the signal. The duty cycle of the signal will vary in proportion to the position of the blade control handle.
Blade Pitch Position Sensor (If Equipped)
| |
| Illustration 4 | g02443256 |
| (22) Thumb Roller | |
Pitching the blade forward and backward is controlled by the position sensor that is located on the thumb roller (22) of the blade control handle. The Implement ECM receives a PWM duty cycle change from this sensor, when the handle is moved along the thumb roller direction. The Implement ECM will process this signal to provide an output to the blade tilt solenoids to pitch the blade. The solenoids will pitch the blade to the position that is commanded by the signal. The duty cycle of the signal will vary in proportion to the position of the thumb roller.
| |
| Illustration 5 | g02794209 |
The blade shake trigger switch has a normally closed and a normally open contact. Press the blade shake trigger button in order to activate the feature. Pressing the blade shake button overrides the handle tilt command. Blade shake is active when the button is pressed. Blade shake can be active for a maximum of 8 seconds. This feature is not available when Accugrade is configured on the machine.
Automatic Blade Control / Manual Blade Control / Decrement Switch
| |
| Illustration 6 | g02595216 |
The automatic blade control / manual blade control / decrement switch is a single pole switch with a common return. The switch is the left of the two pushbutton switches on the implement handle. Pressing the switch engages automatic blade control or manual blade control when Accugrade is configured on the machine. Pressing the blade shake trigger in combination with this switch causes the blade level to decrement when Accugrade is configured on the machine.
The increment switch is a single pole switch with a common return. The switch is the right of the two pushbutton switches on the implement handle. Pressing the blade shake trigger in combination with this switch causes the blade level to increment when Accugrade is configured on the machine.
Rear Implement Control Handle Position Sensors
| |
| Illustration 7 | g01974677 |
|
(6) Gated position sensor base assembly
(7) Control handle for the rear implement | |
The rear implement control lever is used to control the rear implement. The output from the implement control is input to the Implement ECM. The ECM will control the implement solenoids for the rear implement that is attached to the machine. When the lever is moved, the PWM sensors in the base of the lever will communicate the movement of the lever to the Implement ECM. The sensors will indicate movement along the X-axis and the Y-axis. Movement is indicated as a change in the duty cycle of the PWM output of the position sensors. The Implement ECM will use this information to control the hydraulics for the implement according to the command of the signal. The frequency of the PWM signal is constant at 500 Hz. The machine electrical system provides +battery voltage to the sensor for operating power. The sensor may be calibrated with Cat ET. For more information, refer to Testing and Adjusting, "Calibration".
| |
| Illustration 8 | g01995334 |
|
Ripper controls (8) Hold (9) Lower (10) Shank out (11) Raise (12) Shank in (13) Auto Stow | |
| |
| Illustration 9 | g01995335 |
|
Winch controls (14) Hold (15) Drum Clutch Release (16) Reel Out (17) Cancel Drum Clutch Release (18) Reel In (19) Low Speed Lock | |
Three Function Auxiliary Control Handle
| |
| Illustration 10 | g01974855 |
|
(20) Non-gated position sensor base assembly
(21) Control handle for the rear implement with thumb wheel | |
| |
| Illustration 11 | g01458656 |
|
Location of the Fuel Level Sensor (arrow) on the top of the fuel tank | |
| |
| Illustration 12 | g02467498 |
|
Fuel Level Sensor input connections to the Machine ECM | |
The Implement ECM monitors the voltage of the Fuel Level Sensor to determine the amount of fuel that is in the fuel tank. The ECM associates the voltage value of the sensor with a specific amount of fuel in the fuel tank. The ECM sends this information to the Message Display over the J1939 CAN A Data Link circuits. The Message Display will display the amount of fuel that is in the fuel tank on the fuel gauge.
When the fuel tank is nearly empty, the voltage from the sensor is approximately 0.5 VDC. When the fuel tank is nearly full, the voltage from the sensor is approximately 4.0 VDC.
Hydraulic Main Pump Pressure Sensor
| |
| Illustration 13 | g01974863 |
The pressure of the hydraulic oil corresponds to the voltage signal of the sensor. The voltage signal is input to the Implement ECM. The changes in the voltage represent changes in the hydraulic oil pressure. The hydraulic oil pressure is displayed on the Message Display.
Hydraulic Oil Temperature Sensor
| |
| Illustration 14 | g01974864 |
The temperature of the hydraulic oil corresponds to the voltage signal of the sensor. The voltage signal is an input to the Implement ECM. The changes in the voltage represent changes in the hydraulic oil temperature. The temperature of the sensor is displayed on the Message Display. The temperature is represented in Metric units or English units.
Temperature Sensor for the Evaporator of the Air Conditioner
| |
| Illustration 15 | g01974867 |
The temperature of the fins of the evaporator core corresponds to the voltage signal of the sensor. The sensor is an input to the Implement ECM. A change in the temperature of the evaporator core fin is represented by a change in resistance. This information is used by the Implement ECM to control the speed of the compressor.
Ambient Air Temperature Sensor
|
| |
| Illustration 16 | g01974864 |
The ambient air temperature measures the ambient air temperature around the compressor. The signal for the temperature is used turn off the compressor if the temperature is below
Hydraulic Oil Filter Bypass Switch
| |
| Illustration 17 | g01974869 |
The hydraulic filter bypass switch is a pressure switch that shows when the filter is plugged and the filter is being bypassed. The switch is normally open. When the filter becomes plugged, the increased oil pressure will bypass the filter. The state of the switch changes as a result of the increased pressure and the operator is alerted of the condition.
| |
| Illustration 18 | g01974870 |
The lockout switch for the winch is designed to disable the winch controls electronically. The switch should be in the LOCKED position before any of the following conditions occur:
- The operator exits the machine.
- The machine is serviced.
- The machine is left unattended.
The switch affects the system in the following manner:
LOCKED - The ECM ignores commands that are sent from the winch controls.
UNLOCKED - The ECM recognizes commands that are sent from the winch controls. The functionality of the winch is enabled.
The switch has a normally closed contact and a normally open contact. The ECM can always determine whether the switch is in the LOCKED position or the UNLOCKED position. The two input circuits are used for diagnostic purposes. The ECM detects a failure in the circuit if the two circuits of the switch are in the same state. The ECM records a diagnostic code in the event of a failure.
| |
| Illustration 19 | g02480376 |
The implement lockout switch is designed to de-energize the implement pilot supply solenoid. The ECM provides the electrical power to the solenoid. The ECM de-energizes the implement pilot supply solenoid when the switch is placed in the LOCKED position. The switch should be in the LOCKED position before any of the following conditions occur:
- The operator exits the machine.
- The machine is serviced.
- The machine is left unattended.
The switch affects the system in the following manner:
LOCKED - The implement pilot supply solenoid is de-energized and the commands from the implement control are ignored. The implement system is no longer operable.
UNLOCKED - The implement lockout solenoid is energized. The implement system is enabled.
The switch has a normally closed contact and a normally open contact. The ECM can always determine whether the switch is in the LOCKED position or the UNLOCKED position. The two input circuits are used for diagnostic purposes. The ECM detects a failure in the circuit if the two circuits of the switch are in the same state. The ECM records a diagnostic code in the event of a failure.
| |
| Illustration 20 | g01974872 |
This switch enables the air conditioning system via the Implement ECM. Push the switch to the up position enable the air conditioner. The circuit is closed when the switch is in this state. Push the switch to the down position to disable the air conditioner. The circuit is open when the switch is in this state.
| |
| Illustration 21 | g02485196 |
|
Refrigerant Pressure Switch | |
The refrigerant pressure switch is a normally open switch. As the pressure in the A/C system increases, the switch actuates closed.