DTC P1682: Throttle Actuator Control Module Ignition Out Of Correlation: Description
WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The Engine Control Module (ECM) uses 2 separate circuits to power the Throttle Actuator Control (TAC) system. These two circuits are joined once inside the ECM. Because the ECM connector cavities cannot accept one wire large enough to power the throttle actuator motor, two separate circuits are used to achieve the needed current carrying capacity for the system. The ECM compares the voltage on the combined circuit within the ECM to the Ignition 1 voltage. DTC P1682 will set when the ETC input voltage differs from the Ignition 1 voltage by a predetermined amount.