RETAINER 4T1021 - Caterpillar

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Pulse Width Modulated SignalSpeed Sensors (Transmission and Torque Converter Output)
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Speed SensorThere 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. In the case of dual sensors, the power train ECM receives signals from the speed sensors and the ECM uses the difference in input from the speed sensors in order to determine the direction 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 intermediate speed sensors (if equipped) measure intermediate transmission speed. 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.Reference: For 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.Reference: For more information on the CAT Data Link, refer to the Service Manual module Systems Operation, "CAT Data Link" for the machine that is being serviced.Reference: For 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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Transmission Oil Temperature Sensor (1) Signal wire (2) Ground wireThe transmission oil temperature sensor is a passive sensor. As the temperature of the oil changes, the resistance in the sensor will change. This change in resistance changes the voltage that is seen by the power train ECM for the sensor. The power train ECM measures transmission oil temperature from the voltage of