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jazzmaster, ASE Certified Technician
Category: Chevy
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05 2500 chevy truck code p1125 p2125 p2120

Customer Question

05 2500 chevy truck code p1125 p2125 p2120
Submitted: 6 years ago.
Category: Chevy
Expert:  jazzmaster replied 6 years ago.


hi,with all 3 codes this tells me that there may be a problem with the wiring or a component, you will need to check the circuits of each of the app sensors,there will be a 5 volt supply to each of these app sensors,


The accelerator pedal assembly contains 2 individual APP sensors within the assembly. The APP sensors 1 and 2 are potentiometer type sensors, each with the following circuits:

  • A 5-volt reference circuit
  • A low reference circuit
  • A signal circuit

The APP sensors are used to determine the pedal angle. The control module provides each APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensors then provide the control module with signal voltage proportional to pedal movement. Both APP sensor signal voltages are low at rest position and increase as the pedal is applied.

  • Remove the connector position assurance (CPA) retainer.
  • Disconnect the accelerator pedal position (APP) sensor electrical connector
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  • now with the key on check the wiring values for the 5 volts on the 2 wires you should have 5 volts on each
  • also on the throttle body check for the 5 volts on those 2 wires
  • if you have those voltages check for voltage increasement up(it should go up to 5 volts or close to that) on circuits #1 #11 on the throttlebody and letters F & C on the gas pedal sensor
  • if you have that on one but not the other then that sensor may be bad,also at this time if there is no 5 volt to both or one of these sensors then we will have to get into the app module(TAC module)
  • but for now check those and also check the etc/ecm 15 amp fuse and there should also be a ign 1 relay see if that clicks when you cycle the key on and off
  • you can check the TAC module for the 12 volts in and the 5 vols out and the ground at the tac module too ,at this time just to see if it is getting the 12 volts ignition on signal and sending out the 5 volts,do this if possible with the connector plugged in to the tac module
  • here are the flow charts,diagrams and related pics
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  • Edited by GUY V.I. on 9/6/2010 at 6:36 AM EST