Theory Of Operation

This diagnostic checks for a loss of connection of the sensor ground reference. The common ground reference is provided to all sensors by the Transmission Control Module (TCM) via three different connector pins, named GNDSENS1, GNDSENS2 and GNDSENS3. In order to ensure that the system continues to work properly even if one of the ground pin is disconnected, the most critical sensors have their ground reference connected to both GNDSENS1 and GNDSENS2, so that only a loss of connection of both pins will cause a loss of ability to shift gears. These sensors are the gate select position sensor, the odd and even clutch speed sensors, all the gear actuator position sensors and the even clutch pressure sensor. The odd clutch position sensor, the hydraulic pressure sensor and the park position sensor have instead their ground reference connected to GNDSENS3. When a loss of connection of both GNDSENS1 and GNDSENS2 or only GNDSENS3 is detected, the diagnostic will set a fault in the TCM.