it is not sensing the throttle plate opening/closing completely or is receiving an incorrect signal in comparison to the accelerator pedal position sensor based on what the ECU is expecting to see.
One thing you may want to try is to clean out the carburetor with some carb cleaner to insure the throttle plate is closing completely and not being deflected by dirt keeping it from fully closing.
One other thing you can try is to remove the cover on the motor control on the throttle and check the gear area and make sure it has lube, some throttle assy's had issues with poor lubrication and would cause the mechanism to bind creating the scenario triggering the code.
The worse case is you would have to replace the carburetor/throttle assy.

Depending on which ECU it has there is a diagnostic tester you can obtain from cat part number: 9186802300 and determine the codes stored and which procedure from the service manual to perform to correctly diagnose and clear the codes and identify exactly what the problem is.