Accelerator Pedal Position Sensor
WARNING: This page does not describe the selected car, but rather 31 other vehicles, including the 2003 Mercury Sable, 2003 Mercury Mountaineer, 2003 Mercury Marauder, 2003 Mercury Grand Marquis, and 2003 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.
See TEST DK: ELECTRONIC THROTTLE CONTROL & ACCELERATOR PEDAL POSITION SENSOR under SYSTEM TESTS in SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article for Accelerator Pedal Position (APP) sensor testing procedures and specifications.