All three Code Definitions are in the CVT Transmission Control Module section of the Factory Service Manual :
U1407-IMPLAUSIBLE ENGINE TORQUE REQUEST SIGNAL RECEIVED
U1424-IMPLAUSIBLE ENGINE TORQUE SIGNAL RECEIVED
U1425-IMPLAUSIBLE PEDAL POSITION SIGNAL RECEIVED\
Diagnostic steps, utilizing a scan tool, start out the same for all three codes:
- Always perform the CVT Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Transmission Control (TCM) - Standard Procedure)
Then, the manual takes you through the scan tool diagnostic steps to determine :
- TOTALLY INTEGRATED POWER MODULE (TIPM) CAN BUS DTCS PRESENT
- ENGINE MODULE DTCS PRESENT
- POWERTRAIN CONTROL MODULE (PCM)
- TRANSMISSION CONTROL MODULE (TCM)
For each of the 4 possible problem areas above, the manual walks you through a Yes/No process and you proceed to the next step depending what the scan tool tells you. Along the way, the manual give you areas to check, such as wiring pins, harnesses, etc.. Once you determine which of the above 4 are giving the DTC, then you proceed to that section and start a specific diagnostic process for that.....I.E., the TCM if that is where you are lead to.
There's not much more I can assist with, without copying the entire section of the Factory Service Manual.
The throttle body on these have some plastic gears in them that have been known to cause this type of symptom(s). A new one is under $250 and it IS DIY possible. BUT......without properly diagnosing the problem, you might end up wasting more money throwing random parts at the problem. What if its just one loose wire????