Circuit Description
WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
The Engine Control Module (ECM) controls the throttle blades by applying a varying voltage to the throttle valve motor. The ECM monitors the actual throttle blade position using Throttle Position (TP) sensor 1 and 2. If the ECM detects the throttle blade did not return to the rest position during the learn procedure, DTC P1551 sets.