DTC P0121: Throttle/Pedal Position Sensor A Circuit Range/Performance

WARNING: This page does not describe the selected car, but rather 33 other vehicles, including the 2010 Mercury Mountaineer, 2010 Mercury Milan, 2010 Mercury Mariner, 2010 Mercury Grand Marquis, and 2010 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0121: THROTTLE/PEDAL POSITION SENSOR A CIRCUIT RANGE/PERFORMANCE

For Vehicles With An Idle Air Control (IAC) Valve
Description:	The throttle position (TP) sensor circuit is monitored by the powertrain control module (PCM) for a non-closed throttle position at idle. The test fails if the key on engine running (KOER) self-test terminates upon placing the transmission gear selector in DRIVE or REVERSE or the TP closed throttle position is not achieved when closing the throttle (idle) after opening it (in PARK or NEUTRAL).
Possible Causes:	Binding throttle linkage Damaged throttle body TP circuit open to PCM Damaged TP sensor SIG RTN circuit open to the TP sensor
Diagnostic Aids:	Drive the vehicle, bring it to a stop, and turn the ignition to the OFF position. Start the engine, and run the KOER self-test at idle.
For All Others
Description:	The electronic throttle control (ETC) throttle position (TP) sensor 1 circuit was flagged as a concern by the powertrain control module (PCM) indicating an out of range in either the closed or wide open throttle (WOT) modes.
Possible Causes:	Obstruction in the throttle plate movement Damaged throttle body TP circuit open to PCM Damaged TP sensor Self-test operator error (foot resting on the accelerator pedal during test)
Diagnostic Aids:	This concern exhibits a symptom of limited power.
Application	Key On Engine Off	Key On Engine Running	Continuous Memory
Ranger	GO to PINPOINT TEST DH .
All others	GO to PINPOINT TEST DV .