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The problem is in the Throttle Body or wiring. It has nothing to do with the pedal sensor (APP), that's a whole different set of codes. The TB has two potentiometers built in which work opposite one another, see the graph below:
Font Rectangle Material property Parallel Slope

The reason the system is configured that way is because the percentage difference between the two signals will be the same at any supply voltage, even though the "height" of the X is different. That allows the ECM to compensate for any problems in the 5V sensor supply. The P2135 is telling you neither one of the signals is flatlined (that would cause a P0122 or P0123) but one of them is producing an incorrect voltage. Some Nissans have separate supplies and grounds for each of the sensors, but on VQ Altimas the power and ground is common:
Rectangle Line Parallel Font Slope

That means problems in the 5V supply or ground can't affect just one sensor. So the cause of the problem is limited to a bad signal wire from a sensor to the ECM, or a bad pot in the TB (in which case you need a new TB). Here's the layout for the TB connector (note that the WD has a typo, the connector is actually F57):
Font Rectangle Line Material property Parallel

Pins 2 and 3 should show voltages approximating what's on the graph at various throttle positions. If they do then you have a bad wire, if they don't then you have a bad TB.
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