P0121 - Throttle/Pedal Position Sensor A Circuit Range/Performance

WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2008 Mercury Sable, 2008 Mercury Mountaineer, 2008 Mercury Milan, 2008 Mercury Mariner, and 2008 Mercury Grand Marquis. However, it is still accessible from the selected car via links, so may be relevant.

P0121 - THROTTLE/PEDAL POSITION SENSOR A CIRCUIT RANGE/PERFORMANCE

For Vehicles With Electronic Throttle Control (ETC)
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 SIG RTN circuit open to the TP sensor Self-test operator error (foot resting on the accelerator pedal during test)
Diagnostic Aids:	This concern exhibits a symptom of limited power.
For All Others
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 key to the OFF position. Start the vehicle, and run the KOER self-test at idle.
Application		Key On Engine Off	Key On Engine Running	Continuous Memory
Vehicles With Electronic Throttle Control (ETC)		refer to PINPOINT TEST DV .
All others		refer to PINPOINT TEST DH .