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Jay, Nissan Technician
Category: Nissan
Satisfied Customers: 20399
Experience:  20+yrs experience with Nissan & Infiniti Trained & Certified.Currently still working for Dealer
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my 2004 nissan altima transmission is not shifting ,i recently

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my 2004 nissan altima transmission is not shifting ,i recently went to autozone and code p0725 came up which is a engine speed signal code, however there is no such part. the car goes into drive and reverse but the transmission is not shifting , is the problem a tcm box which was told to me buy a local mechanic who wants to chrge a arm and leg to order please help.Also a code u1001 came up and was unable to be recognized (what is it)

semcondly, where is the park/neutral position switch,circuit sensor located code P1706 is on the list also
Hello and thank you for using

Sounds like you have a few things going on. First off the U1001 is a communication problem between one of the 5 control units for your car. Since your having transmission issues I am guessing the transmission control unit. You will need to have advanced level diagnostics to perform what they call a CAN TEST. The U1001 and U1000 are CAN codes which only show when the computer can not communicate with another control unit. All 5 control units talk to each other on what they call a CAN line. If a control unit isn't talking, that is when you get that code. I would start by having this advanced level test done. You will need a advanced level scanner that can perform this. This is the first place you need to start with your problem as well as checking all fuses.

If you have any more questions on this, please feel free to ask. Thanks Jay!
Customer: replied 7 years ago.
where is the transmission conrol unit and where can i buy it if needed. is this something a licensed mechanic can do r does it have to go to a dealer. Also what fuses need to be checked all three locations or one location particular.
I would use a test light and check all fuses. I also would have the TCM ( Transmission Control Module ) checked to see if it's communicating properly. It's located next to the Ecm behind the glove box.This is a dealer item. It is best to be replaced with the proper part number. You can get a used one, but you won't know if it's the same part number till installed and read from a advanced level scanner to determine if it's correct, since part numbers are not stamped on the out side of the Ecm or Tcm.

If you have any more questions on this, please feel free to ask. Thanks Jay!
Customer: replied 7 years ago.
one more question jay where is the park/neutral switch located i have that code also but i have no problems with this however i will change if needed
The park nuetral switch rarely never fail. I think I have only seen 2 in my 20 years go bad. I think it may be a false code due to the CAN issue. It's located on the front of the transmission where the shifter cable goes. But I would not look at that yet. Here is it's location.graphic

Thanks Jay!
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Customer: replied 7 years ago.
o.k. jay the car is shifting now however after driving maybe an hour the car stops shifting if i stop at a stop sign or red light. I can pull on the side of the road and wait maybe three minutes and start the car back up and it shifts o.k. again until i have to stop at a light or stop sign. Can you tell me if i have another tcm and control module which is located under the passenger side dash behind the glove box from another car will it work or not. Also how much does Nissan usually charge to perform this can test and how much does this repair and part usually cost. i'm low on money and some things i can do myself if i'm pointed in the right direction
Well, if the transmission stops shifting, you may have some internal issues developing as well. A dealer will charge 1 to 2 hours labor for diag of the Can system. I would also do a transmission pressure check to make sure the internal parts of the trans are ok.

Thanks Jay!