Thanks for the question.
P1515 = Commanded vs. Actual throttle position.
The commanded throttle position is compared to the actual throttle position based on the accelerator pedal position. Both values should be within a calibrated range of each other. The PCM continusly monitors these positions. This code will set if the values are higher than there calibrated range.
P1512 = Intake manifold runner control stuck closed.
The description for this is the same as P1515.
This leads me to believe that there is a problem with either that accel pedal or the throttle body. There have been some known issues with the accel pedal though.
There was some information about setting codes similar to these, due to the state of charge with the battery as well.
I hope this helps,
There are 2 sensors in the accel pedal that send the pedal position to the computer. They corrilate with each othere and have to be in the correct range. If the 2 sensor are out of calibration, it will set a code. This may not be the case on your vehicle, just some added information.
The diagnostic steps for the P1512 point to the throttle body for replacement. This will be hard to diagnosis because a scan tool that can read PCM data values is needed. Everything has to do with the PCM reading the correct values of all these parts. The only way to tell what the PCM is "seeing" is to use a really high end scan tool.