Theory Of Operation
WARNING: This page is about a different car, the 2006 Dodge Magnum, 2006 Dodge Charger, and 2006 Chrysler 300. However, it is still accessible from the selected car via links, so may be relevant.
The two speed sensors in the transmission system and use a common ground circuit. The loss of this common ground results in the input signal being sensed by both sensors. After a reset and in neutral, and observing a certain Output/Input ratio will increment the Speed Check Fault Counter. Because the speed sensors and the thermistor share the same ground wire, this DTC may indicate a loss of the common speed sensor ground. In some cases this fault will cause a Gear Ratio Error DTC to be set.