P0121 GMC -

Question

had this code p0121..so i check voltage supply 12v ok..check voltage range on tpsensor 1 3.45-1.11 tpsensor 2 .03-1.6 at the app sensors i got app sensor 11.03-4.5 at app sensor2 .05-2.1... so i replaced the throttle acuator control, no more check engine light, but i get high rpms in park..i have to keep putting in drive then i can place it in park and rpms will be normal...wtf/

Answer 1

P0121 Throttle position sensor / Switch A circuit range

TPS 1 sensor signal  this is the DRK green wire at closed throttle should be above 4 volts and decreases as the throttle plate is opened TPS 2 is the Purple wire at closed throttle should be below 1 volt and increase as the throttle plate is open

APP 1 should be  0.33 at idle 4.59 WOT  (DRK blue wire)

APP2 should be 0.16 at idle 2.30 WOT ( Lt blue wire)

 Check to see if the throttle plate has a bind, clean it out using brake cleaner or throttle body cleaner, for some reason your higher at TPS 1 and APP1