Nissan Repair: Whats causing fault codes P0325, P0732 and P0105?, nissan maxima, nissan vehicles

Question
I have a 1998 Nissan Maxima with the fault codes:
P0325 Knock sensor 1 Circuit malfunction bank 1 or  1 sensor
P0732 Gear 2 ratio incorrect
P0105 MAP/BARO Circuit malfunction

Car usually drives ok, but the other morning after I started my car and put it into reverse, the engine just died right away. I started it again and tried both putting it into reverse and then drive and the engine continued to shut down. I started it again and let it idle in park for about 2 minutes and finally was able to drive it a little bit but it soon died again when I slowed the car to about 15mph. I started it once again and let it run idle until the engine warmed (for about 5 min) and I was able to drive the car with no further problems. I only seem to have these problems when the engine has not had a chance to warm up, but after the car drives ok. I assume what i am experiencing is related to the error codes. Any ideas what the causes of these problems are and how much to fix?

Answer
Marcus,

I would change the knock sensor.  Nissan vehicles are known for this after many years.

The second code could be a problem.  Sounds like second gear is slipping.  That could be nothing since the engine is doing strange things due to the other codes.  Leave this to the last.  Wait until the other things are corrected and see if this one corrects itself.  If not it is transmission diagnostic time.

The MAP (manifold absolute pressure sensor) and it needs to be replaced.