View Full Version : P0121 trouble code

May 6th, 2012, 11:02
a few days ago, my wife calls and says she had no problems with 99 2wd auto cherokee. she parks jeep for about an hour, goes to leave and tries to start up and jeep just stalls out. check engine comes on and she cant start up. she gets a jump and starts up ok, able to drive home. just checked codes, only one that comes on is P0121. problem hasnt returned, and sounds and runs ok.

O-Gauge Steamer
May 7th, 2012, 07:59
P0121 JEEP Description
The throttle position sensor (TPS) responds to the accelerator pedal movement. This sensor is a kind of potentiometer which transforms the throttle position into output voltage, and emits the voltage signal to the Engine Control Module (ECM). In addition, the sensor detects the opening and closing speed of the throttle valve and feeds the voltage signal to the ECM.

Idle position of the throttle valve is determined by the ECM receiving the signal from the throttle position sensor. This sensor controls engine operation such as fuel cut. On the other hand, the Wide open and closed throttle position switch, which is built into the throttle position sensor unit, is not used for engine control.

Read more: http://engine-codes.com/p0121_jeep.html#ixzz1uByWoFKz

Possible causes
- Throttle position sensor harness is open or shorted
- Throttle position sensor circuit poor electrical connection
- Faulty throttle position sensor
- Faulty Engine Control Module (ECM)

Read more: http://engine-codes.com/p0121_jeep.html#ixzz1uByNrQcB

It may be time to reseat the TPS connector. Inspect it for corrosion whilst disonnected.