As with any nissan Tier II and above engine control system the throttle valve and accelerator learning has to be done along with the air idle volume learning.

This is the caterpillar learning methods
Nissan may be the same, if not then you will need to get the proceedure out of the Nissan service manual.

To do the throttle valve closed position learning all you do is turn on the key (do not start the engine), then turn it off. Wait 5 seconds.
Make sure the throttle moves, you should hear it buzzing when it is learning, just a couple seconds. When it is complete it will stop.

Accelerator pedal position released position learning:
-turn ignition on and wait 2 seconds
- turn ignition off, wait 10 seconds
-turn ignition on and wait 2 seconds.

The air idle volume learning is done as follows:
(This has to be done with the service tool or pc program)
this will not keep the engine from accelerating though.