Nissan Repair: 98 nissan service engine soon and ac switch, nissan service, speed purchase

Question
#1 My granddaughter car service engine soon light came on at 88,000 miles. We had it checked at Auto Zone and it had a code of P0120. My husband changed the throttle sensor but the light is still on.
#2 The knob that turns on the a/c does not work in position 1,2 or 3.. but works on 4(hi)only. We changed the fan switch but it still does the same.
What do you recommend for both situations?

Answer
Rose,

First, disconnect the battery for five minutes and that should clear the code for the P0120.  For the blower motor you need to replace the resistor that is used to control the fan speeds.  Under the dash, on the passenger side, there is a unit that has the resistors that control the fan speed.  Purchase a new one and you will see what needs to be replaced.  It is under the dash, behind the glovebox.  Two screws hold it on.  So, it is just a matter of replacing the old one with the new one and the blower should work on all speeds.