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| Illustration 1 | g01289742 |
(1) Speed Sensor (Torque Converter Output Speed) (2) Speed Sensor (Engine Output Speed) (3) Transmission Planetary Output Speed | |
There are two transmission output speed sensors (3), one engine speed sensor (2) and one torque converter output speed sensor (1) on the machine. These speed sensors send an AC frequency signal (HZ) that matches the number of gear teeth passing the sensor per second to the ECM. The ECM compares the frequency from the speed sensor (HZ) to the number of pulses per revolution in order to determine the speed of the rotating components. The ECM uses the input from the speed sensors in order to regulate transmission shifts.
Each speed sensor has two connections to the ECM (+ and −). 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 (3) in order to provide protection against failure.
Note: The speed sensors are used to diagnose each other during normal operation. The ECM periodically checks the value from the speed sensor. If an incorrect value is found, the ECM will log a service code that indicates a fault for a speed sensor circuit.