P0121 CODE ON 2007 AVALANCHE LT

Hello everyone, I'm a new member to this forum and i'm looking for guidence please. Got an engine LT on my AVY for some time now thus not allowing me to use my command start. I hooked up my scan tool and got a P0121 (Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance) message. Now I did some research and it points me in the direction of the Throttle Pedal Position Sensor as the most likely culprit. Now I called around for the part and after talking to a local tech, he suggested that it might be the Throttle Position Sensor on the throttle body as he has several in stock and his notes indicated thats most likely the problem... so I baught it, and installed it without proplem only to have the engine light come on again. I found  the throttle pedal but would like your advice if it could be anything other than that as I don't want to spend more money on parts that don't fix the problem. I'm not experiencing any reduction in power just the engine LT with above code and not being able to use my command start.

Thank you and sorry for the long winded explaination

Could be wiring

Hook your scan tool back up and go to the screen that displays sensor values. You should see the TPS listed there with a voltage reading. At idle it should be 0.5 volts and at full throttle should be 4.5.

Check this article for some additional information.

https://www.obd-codes.com/p0121

Thank you for the info. To date I replaced both the TPS at the throttle body and the TPS accelerator pedal assembly with the code not going away after I reset the light. I've been trying to trouble shoot this b$@$$ for some time hence the replacement of the noted
Parts. I'll trouble shoot the wiring next along with looking at the voltages. By chance do your is which pin on the TPS connectors has the 5 v signal ?