Q: While in park my Nissan idles from 1500-2000 rapidly even after the resetting what could be the problem ?

You can attempt to drive the vehicle and see if re-learning is possibly completed. If driving the vehicle does not resolve the issue, that is the correct idle speed is not attained, check to be sure that the throttle body part number (as printed on the throttle body, not the box), that you installed for your vehicle is correct for your model. To minimize diagnostic headaches, it is always best to buy the part from the dealer. If you have a re-manufactured throttle body it could be defective. If you have the correct throttle body, re-perform the learning procedure, paying particular attention to the check engine light instructions toward the end of this tutorial on Altima throttle body relearning. Be sure to follow each step exactly. If after re-doing the learning routine, you still have the same high idle issue, you either have a defective throttle body or you have one or more of the following issues: a vacuum leak, EGR system malfunctions, malfunctioning oxygen sensors, dirty fuel injectors, fuel pump malfunction, faulty spark plugs, a faulty mass airflow sensor, or a faulty throttle (accelerator) position sensor. The root cause can be pinpointed, and the required repairs made, if you request an engine diagnostic. If you have further questions or concerns, do not hesitate to re-contact YourMechanic because we want you to make the most of your repair dollars and help you to get the best possible results.