Switches
Switches provide three types of switch inputs to the power train electronic control module (ECM), an open signal, a ground signal, or a +battery signal. Switches are open or closed.
- When the switch is open, no signal is provided to the corresponding input of the power train ECM.
- When a switch is closed, a ground signal or a +battery signal is provided to the corresponding input of the power train ECM.
Switch (Engine Deceleration)
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| Illustration 1 | g00878187 |
Switch for the Engine Deceleration (1) Open connection (2) Ground (3) Indicator light (4) Open connection (5) Sensor return (ECM) (6) Closed connection (A) Signal for deceleration (B) Ground | |
The switch for the decelerator is an input to the power train electronic control module (ECM). The switch will disable the function for engine deceleration or the switch will enable the function for engine deceleration.
The switch for the engine deceleration is an on/off switch. When the switch is activated, contact J1-21 will be connected to the +Battery connection and the decelerator is disabled. The decelerator will stay disabled until the switch is shut off. Terminal A and terminal B turn on the internal switch indicator.
ReferenceFor more information on the function for engine deceleration, refer to the Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.
ReferenceFor more information on the function of the power train ECM, refer to the Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.
Pressure Switch (Parking Brake Oil)
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| Illustration 2 | g00287701 |
Parking Brake Pressure Switch | |
The parking brake pressure switch is an input of the power train electronic control module (ECM). This switch informs the power train ECM when the parking brake is engaged.
The parking brake pressure switch is a double-pole, single-throw pressure switch. When the operator engages the parking brake, the normally open (N/O) pole opens and the normally closed (N/C) pole closes to ground. This tells the power train ECM that the parking brake is engaged. When the parking brake is disengaged, the N/O pole is closed and the N/C pole is open. This tells the power train ECM that the parking brake pressure switch circuit is operating correctly. No action is required. The N/C pole connects to connector contact J1-27 of the power train ECM. The N/O pole connects to connector contact J1-36 of the power train ECM. The common terminal of the switch connects to ground.
Note: The normally closed (N/C) circuit and normally open (N/O) circuit of the parking brake pressure switch are used for diagnostic purposes. A circuit failure is present if the two circuits are open at the same time or if the two circuits are grounded at the same time. This fault is then shown on the display of the power train ECM.
ReferenceFor more information on the diagnostic operations, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.
ReferenceFor more information on the parking brake function, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.
ReferenceFor more information on the function of the power train ECM, refer to Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.
Switch (Transmission Direction and Speed Control Lever)
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| Illustration 3 | g00878362 |
Transmission Direction and Speed Control Lever | |
The switches in the transmission direction and speed control lever are inputs to the power train electronic control module (ECM). The switches send information to the power train ECM about the speed that has been selected and the direction that has been selected with the transmission direction and speed control lever. The switches close the direction/speed inputs to ground on the power train ECM.
ReferenceFor more information on the function of the transmission direction and speed control lever, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.
ReferenceFor more information on the function of the power train ECM, refer to Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.
Switch (Upshift/Downshift Switch)
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| Illustration 4 | g00878364 |
The upshift/downshift switch signals the power train electronic control module (ECM) to manually shift the transmission by one speed. When the speed control lever is set in second speed, the upshift/downshift switch will downshift to the first speed position. As the operator depresses the upshift/downshift switch repeatedly, the transmission will toggle between first speed and second speed. After a direction shift, the transmission will return to second speed.
ReferenceFor more information on the function of the upshift/downshift switch for the transmission, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.
ReferenceFor more information on the function of the power train ECM, refer to Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.
Start Switch (Key)
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| Illustration 5 | g00291705 |
Key Start Switch | |
The key start switch is an input of the power train electronic control module (ECM). The key start switch informs the power train ECM of an attempt to start the engine. The power train ECM then initiates the neutral start function.
During normal machine operation, the start terminal of the key start switch is open. When the key start switch is turned to the START position, the start terminal closes to the +battery and the +battery voltage is present at connector contact J1-40 of the power train ECM. When all starting conditions are satisfied, the power train ECM sends a +battery signal to the connector contact J1-8 for the start relay and engine cranking begins.
Note: After the key start switch is initially turned to the START position, the switch will not return to the START position from the ON position. The switch must be turned to the OFF position first. Then, the switch can be turned to the START position.
ReferenceFor more information on the neutral start function, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.
ReferenceFor more information on the function of the power train ECM, refer to Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.
Sensors
Sensors provide information to the power train electronic control module (ECM) about changing conditions. The sensor signal changes proportionally to the changing conditions. The following type of sensor signals are recognized by the power train ECM.
- Frequency signals: The frequency (Hz) of the sensor signal varies as the condition changes.
- Pulse width modulated signals (PWM): The duty cycle of the sensor signal varies as the condition changes. The frequency of this signal is constant.
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| Illustration 6 | g00288430 |
Pulse Width Modulated Signal | |
Speed Sensors (Transmission and Torque Converter Output)
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| Illustration 7 | g00288428 |
Speed Sensor | |
There are two transmission speed sensors and one torque converter output speed sensor on the machine. The speed sensors are inputs of the power train ECM. These speed sensors are frequency sensors. Frequency sensors produce a signal (Hz) which varies as the condition changes. The sensor generates an approximate sine wave signal from the gear teeth as the gear teeth pass the sensor. The sensor produces a signal that equals one pulse per gear tooth. This signal is sent to the power train ECM. The power train ECM measures the frequency of the signal in order to determine the speed of the condition. The power train ECM receives signals from the speed sensors. The power train ECM uses the input from the speed sensors in order to determine the speed of the system. The power train ECM uses the input from the speed sensors in order to regulate transmission shifts. Each speed sensor has two connections to the power train ECM (+ and −).
The power train ECM sends the speed information to other electronic control modules via the CAT Data Link. For all of the speed sensors, connector contact 2 is the signal line and connector contact 1 is the return line. Two transmission speed sensors measure transmission output speed. The power train ECM uses the pairs of speed sensors to determine the direction of rotation.
Note: The speed sensors are used to diagnose each other during normal operation. The power train ECM periodically checks the value from the speed sensor. If an incorrect value is found, the power train ECM will log a service code that indicates a fault for a speed sensor circuit.
ReferenceFor more information on diagnostic operations for the power train electronic control system, refer to Systems Operation, "Power Train Electronic Control System" for the machine that is being serviced.
ReferenceFor more information on the CAT Data Link, refer to the Service Manual module Systems Operation, "Data Link" for the machine that is being serviced.
ReferenceFor more information on the power train electronic control module (ECM), refer to the Service Manual module Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.
Temperature Sensor (Transmission Oil )
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| Illustration 8 | g01868113 |
Transmission Oil Temperature Sensor (1) Ground (2) Voltage Supply (3) Signal | |
The transmission oil temperature sensor is a pulse width modulated sensor (PWM). The power train ECM measures transmission oil temperature with the transmission oil temperature sensor. The power train ECM uses the oil temperature reading in order to adjust the shift times of the transmission. The power train ECM adjusts the shift times of the transmission in order to provide smooth shifts over the various ranges of the transmission oil temperature.
ReferenceFor more information on the operation of the machine, refer to the Service Manual module Operation and Maintenance Manual for the machine that is being serviced.
ReferenceFor more information on the power train electronic control module (ECM), refer to the Service Manual module Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.
Position Sensor (Left Pedal) for Engine Deceleration
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| Illustration 9 | g00779650 |
Position Sensor (Left Brake Pedal) | |
The position sensor (left brake pedal) sends an input to the power train ECM. The sensor will continuously update the power train ECM on the position of the left pedal . The left pedal position sends a change in the input signal to the power train ECM. The power train ECM records the change of position. Then, the power train ECM signals the engine ECM via the CAT Data Link. The power train ECM also uses this information in order to neutralize the transmission.
The position sensor (left brake pedal) is a PWM sensor. The sensor continuously generates a PWM signal. The duty cycle varies in proportion to the position of the lever. The power train ECM receives the PWM signal from the position sensor. The power train ECM measures the duty cycle in order to determine the position of the lever. The frequency of the sensor signal is constant at 5000 Hz. The machine electrical system provides +battery voltage to the lever position sensor for operating power.