Sensors provide information to inputs of the ECU about actual transmission conditions. The ECU receives information from the sensor for speed and temperature. The sensor signal will change in order to reflect changes in the monitored condition. The ECU sends out this information on the data link to the instrument clusters and other data link devices. The ECU recognizes three types of sensor signals.
Frequency - The sensor produces an AC signal. The AC signal frequency (Hz) varies as the condition changes.
Pulse width modulated - The sensor produces a digital signal. The duty cycle of the digital signal varies as the condition changes and the frequency of the digital signal is constant.
Voltage - The sensor produces a voltage in reference to the measured condition. A change in the condition results in a change in voltage at the ECU signal input pin.
Torque Converter Temperature Sensor
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| Illustration 1 | g01213764 |
The torque converter temperature sensor that is located on the torque converter is a two wire passive thermistor type sensor. This type of sensor is used to measure the temperatures of the coolant, oil, and the inlet air. As the temperature of the torque converter oil changes, the resistance in the sensor will change. This change in resistance changes the voltage that is seen by the ECU for the sensor.
Transmission Oil Temperature Sensor
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| Illustration 2 | g01213764 |
The transmission oil temperature sensor that is located on the transmission sump is a passive thermistor type sensor that has two wires. As the temperature of the transmission oil changes, the resistance in the sensor will change. This change in resistance changes the voltage that is seen by the transmission ECU for the sensor.
Oil Level Sensor (Transmission)
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| Illustration 3 | g01824773 |
The oil level sensor measures the oil level using the Hall Effect. As fluid enters the bottom of the sensor, the internal float moves axially toward the Hall Effect device. The result is an output signal between 1 V (empty) and 4 V (full) proportional to the fluid level. The sensor connects to the ECU at contact J1-21, contact J1-11, and contact J1-36.
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| Illustration 4 | g01213770 |
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Engine Speed Sensor | |
The engine speed sensor for the transmission is a magnetic sensor.
The engine speed sensor is an input to the ECU. The sensor is designed to inform the ECU about the speed of the engine. The ECU uses the information from the speed sensor in order to calibrate the transmission solenoids. The ECU uses the information from the speed sensor in order to enable the lockup clutch. Also, the information is used in order to disable the lockup clutch. The lockup clutch is turned off if the engine speed is too low. The lockup clutch is turned on if the engine speed is too high. This is done in order to prevent overspeeds of the engine or stalling of the engine.
The engine speed sensor is a frequency sensor. The speed sensor is located on the torque converter housing. The sensor generates an AC signal from the ring gear teeth as the teeth pass the sensor. The ECU measures the frequency of the signal and the ECU responds accordingly to the signal. The engine speed and the diagnostic status of the sensor are available to all modules through the J1939 data link.
The engine speed sensor has a connector with two contacts. The sensor connects to the ECU through contacts J1-2 and contact J1-3.
Transmission Output Speed Sensor (1) and Transmission Output Speed Sensor (2)
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| Illustration 5 | g01213770 |
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Transmission Output Speed Sensor (1) Transmission Output Speed Sensor (2) | |
The transmission output speed sensors are an input to the ECU. The transmission output speed sensor informs the ECU about the speed of the transmission output shaft. The ECU uses the information from the transmission output speed sensors in order to properly shift the transmission. The transmission output speed sensor is a magnetic sensor. The output speed sensor is a “bolt and go” sensor that is a high output speed sensor. There are two output speed sensors for each transmission. The sensors read the same speed. The second sensor provides a backup value in the event of a single sensor failure. The direction is also provided when both sensors are used. The first sensor is spaced off one quarter of a tooth from the second sensor. The space is necessary in order to provide a direction to the ECU. When one of the sensors goes bad or a failure arises a diagnostic code is issued, but a valid output speed is still present. The transmission output speed sensor (1) connects to the ECU through contacts J1-6 and contact J1-7. The transmission output speed sensor (2) connects to the ECU through contacts J1-8 and contact J1-9.
Transmission Input Speed Sensor (Torque Converter Output Speed)
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| Illustration 6 | g01213770 |
The speed sensor is an input to the ECU. The sensor informs the Transmission ECU about the speed of the transmission input shaft. The ECU uses the information from the sensor in order to control the lock-up clutch and validate the signals for the output speed sensors. When this speed sensor fails an amber warning lamp is activated. The ECU also uses the information to aid in calibration of the transmission clutches. The sensor connects to the ECU through contacts J1-4 and contact J1-5.
The ECU records a diagnostic trouble code with the torque converter output speed sensor with a 161-8 diagnostic code..
| Switch Conditions | ||
|---|---|---|
| Switch | Switch State | Action |
| Service Brake | Open | Pedal released |
| Closed | Pedal applied | |
| Parking brake | Open | Pedal released |
| Closed | Pedal applied | |
| Neutral to Gear Inhibit | Open | Feature enabled |
| Closed | Feature disabled | |
| Direction Inhibit | Open | Feature enabled |
| Closed | Feature disabled | |
| Auto Neutral (Single Switch) | Open | Feature enabled |
| Closed | Feature disabled | |
| Auto Neutral (Dual SWG) | Open | Feature enabled |
| Closed | Feature disabled | |
| Shifter Select | Open | Primary shifter |
| Closed | Secondary shifter | |
| PTO Enable | Open | Feature disabled |
| Closed | Feature enabled | |
| Transmission Filter Bypass | Open | Bypassing |
| Closed | Not bypassing | |
| Shifter Display Blank | Open | Display On |
| Closed | Display Off | |
| Retarder Shift Enable | Open | Feature enabled |
| Closed | Feature disabled | |
| Retarder On/Off | Open | Retarder range selection disabled |
| Closed | Retarder range selection enabled | |
| Alternate Start In Gear | Open | Feature disabled and 1st gear is the lowest range |
| Closed | Feature enabled and 2nd gear is the lowest range | |
Switches provide the following types of information to the inputs of the Transmission ECU: open signals, ground signals and +battery signals. Switches are open or closed.
- When a switch is open, no signal is provided to the corresponding input of the ECU. This “no signal” condition is also called “floating”.
- When a switch is closed, a ground signal or a +battery signal is provided to the corresponding input of the ECU.
Bypass Switch (Transmission Filter)
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| Illustration 7 | g01258145 |
The bypass switch is a pressure switch that shows whether the filter is plugged and the filter is being bypassed. This switch is Normally Closed. When the filter becomes plugged the pressure of the oil opens the switch indicating that the oil is bypassing the filter. The switch is spring loaded. When the switch is not installed on a machine the spring forces the switch closed.
The key start switch is an input of the ECU. The switch tells the ECU that the operator wants to start the engine. The ECU then initiates the neutral start function. See Systems Operation, "System Protection Functions" for more information on the neutral start function. See Systems Operation, "Additional Functions" for more information on the starter interlock function. The signal is open during normal operation. When the key start switch is in the START position, the switch is closed to the +battery circuit. Battery power is provided to contact J2-1 when the switch is in the START position.
The ECU records a diagnostic trouble code that occurs with the key start switch as SPN 158 FMI 2. This indicates that the key start switch has been closed too long.