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Nissan Sentra ECM replacement

How do I locate and replpace an ECM (Brain Box / Computer) on a 2002 Sentra "R" model? I can't seem to locate and see the Electronic Control Module right away in order to replace it. Can anyone help me find this part on the car, the chilton's book just says it is on the fire wall. Thank You. -Ty


  • edited October 2009
    Hopefully you are sure the ECU as bad and have proved it before you replace it. Try looking for a box under the dash.
  • edited October 2009
    Yes, Thank you so much for responding to my question. My girlfriend just bought the $600 part from Nissan and is expecting me to get the car up and running so she can go on a road trip for her work. The pressure is on.

    I know from playing with a generic code reader for 45minutes, that the ECM (CPU) has faulty "Read Only Memory" (ROM) (error 'Po605' twice). Also having that much trouble getting a Code reader to communicate with the car indicates a problem with the ECM, and the car is giving all the other semi-mechanical symptoms of an ECM that works intermittently or not at all. Also Nissan performed the recall to "Reprogram" it a few months ago. (it has been giving us trouble ever since, now it doesn't work at all, and Nissan refuses responsibility.)

    If sitting in the driver's seat and looking at the wheel, there is a computer-looking box located behind the steering wheel on the right hand side (in dash behind your right hand). (From what I can see after removing the center panel) from under the steering column, The box has two wire harnesses connecting to the bottom end of the metal box. The box is about the size of my hand.

    Is this box the ECM?

    P.S., when I disconnect the two wire harness with the battery still connected, the car alarm sounds off. and The dealership she bought the part from said we would need to tow the car back after I do the repairs to sync the alarm and power locks and keys.

    Thank you so much for your time and knowledge. -Ty
  • edited October 2009
    It sounds like you found the correct part. Hopefully the problem isn't due to a bad power connection to the unit. You will find out when you put the new one in. You should be able to reprogram the alarm and keyfob yourself I would think. The Owner's Manual should say something on that.
  • edited October 2009
    i am supposed to pick up the part tomorrow at the dealership. I hope it all goes well. When I see the new part, I'll know if i'm taking out the correct old part. it may be on the firewall- under the hood, or, possibly under the passenger side of the dashboard, on the american model- according to the Chilton's book. I hope it is not just an ECM FUSE. wish me luck. either way,


    Anyone with similar problems on the 2000-2004 nissan SE-R, "R" model is welcome to ask any questions on this issue. Thank you for reading, and I hope you learn something from our experiences.
  • edited October 2009
    I did a search of the net about this trouble and found some interesting things. It appears that ECU problems are pretty common for that year and make. It also looks like you may may be able to get your money back on the relacement as the unit may be under warranty for 8 years or 80k miles and there may have been a recall on it. You need to check these things out. I am starting to see why the dealer said it is a problem that Nissan has. You also may want to do your own search of the web about 2002 Nissan ECU problems.

    Another post I saw talked about a common problem with corrodid wires in the wire harness at the lower radiator support that involved the ECU, AC, and horn systems.

    Here is a link for some recall information on the Sentra. One of the recalls refers to the ECU.

    Another link to recalls for the car:
  • edited October 2009
    Ty, It Looks Like There's An ECM Case On The Front Passenger's Side Behind The Strut Tower (Firewall) That Contains The ECM.

    However, I see that Cougar came up with similar information that I did. Are you sure this isn't covered by one of several Recalls or Campaigns pertaining to 2002 Sentras and ECMs? Some Nissans are covered. Nissan has TSBs (Technical Service Bulletins) to help sort this out. Some repairs to problems may not have an expiration, nor a charge.

    Some have had problems with the ECM case and resulting contamination damage to the ECM itself.

    Get your VIN (Vehicle Identification Number) and call your Nissan dealer. I wouldn't touch it until I found out.

    Just curious, Is your girlfriend the car's original owner? How many miles on the Nissan?

  • edited October 2009
    I took out the old ECM today. I did not get all the way because the sun went down and we decided to take it to the dealer after all, they only charge $88 for labor and we would have to tow the car to them any way to do the initial program on it. (plus they have insurance and warranties.)

    Here is what I learned.

    How to Locate and Identify the Electronic Control Module / Unit :
    The ECM, or ECU, is inside the Black plastic box seen when you open the hood, on the american passenger side of the vehicle, at the top of the firewall. The Black plastic housing goes about 8 or 10 inches into the firewall, so you will only see 3 or 4 inches of it sticking out and it is about 8 or 10 inches wide and oddly shaped with a thick wire harness coming from under the driver-side corner of it and a different black rubber tube (about 2 inches thick) coming from the fire wall below it and going into the center of the ECM housing - this is hollow and most likely an Air conditioning duct to cool the ECM. On this car, the A/C tube was not connected, so moisture and heat where probably what killed the ECM (Considering we live in a Hot and Rainy southern state).

    How to Replace the ECM:
    You will need:
      a ratchet with deep socket 10mm
      a deep socket 12mm and/or 14mm
      and a long extension always makes things easier, but not necessary.
      Also you will need the new ECM, ours cost $630 after taxes for the brand new one from a Nissan Dealership with a 1 year warranty, however I have read about people getting a used one purchased from a junk yard for much less.

    (*) But First, it is always super smart to call the auto manufacturer's customer service 800 number and find out if it is covered under any warranties and better yet, if there are any open recalls by giving them your VIN. This may all be free and then some. You never know, something that has just recently been recalled may be causing the problem and everything it effects may be replaced, with a new warranty on the new parts and labor, for $0.

    (A) First, Always disconnect the Negative Battery terminal!
    (B) Then Remove the big black bar connecting the two strut towers, this requires a 12mm or 14 mm deep socket wrench and I used my ratchet handle to gradually pry the different ends of the bar up. You will probably need to "torque" the bar back on the studs when you go to put it back together later, this means lightly Stomp on the bar or use a big rubber mallet to get it back on there.
    (C) Next, you will see a wire harness holder with two (2) 10mm bolts with out washers going into the top of the passenger side strut tower. remove these bolts, the wire harness will be able to move later.
    (D) Next, Disconnect the the Black rubber tube going into the bottom of the ECM housing. Do this by squeezing the upper connection with your hand, and pulling or wiggling it straight downward.
    (E) Now you can remove the two or three 10mm bolts with washers from the firewall. There is one on both top corners and maybe one in the bottom middle. Removing these will allow you to pull the ECM housing out of the firewall. You may want to remove other parts or other wire harness holders to give you more room.
    (F) Next, remove the 10mm bolts with washers that are holding the upper and lower halves of the ECM housing together, Don't forget to hold open the plastic clip on the front of the housing when trying to open it. This was as far as I got before it was too dark to see what I was doing, so I put it all back together by feel.

    (G) The Chilton's Repair Manual simply said (hopefully from this last step) to just "Disconnect wire harnesses from ECM and remove faulty ECM, Installation is reverse order".

    The Chilton's book also forgot to mention that the car will behave unpredictably and will not recognize the gas pedal ( 'Drive-by-wire' configuration, first gear only for those of you who have a drive-by-cable configuration ), and is essentially dangerous to itself and not drivable until the Dealership programs the new ECM. I talked to many mechanics today about doing this and they all said they would do the labor for about $65, but there is no way around it, we MUST tow it to the dealership to have it programmed after the repairs are made. And the manager of the Nissan Service Department also said it is common for local mechanics to tow cars in for this initial programming procedure. Also the dealer sometimes charges about $60 for the reprogramming, sometimes they don't bother charging if they are having a good day plus you brought them home-made brownies or pumpkin pie. because they just plug it into a computer machine and it only takes about 10 or 15 minutes. So, If you decide to take it to a dealership to have it replaced, and you already bought the ECM separately, they will charge you $88 for labor, plus $60 for programming the ECM plus maybe an additional $95 for "diagnostic check"(whatever that means). Be ready to pay for towing too. But, more than likely your Nissan is either still under warranty or even more likely, it has several open recalls on it. Always check for recalls by calling the 800 number for the Nissan North America Customer service line and giving them your VIN.

    Good Luck! I hope this helps someone.

    Thanks for reading and Actively trying to help me. You guys are awesome. I cannot believe the help and advise I got from strangers on here. Thank you so much.

    I heard about all the recalls including some that this VIN was not eligible for, like the foam inside the ECU causing corrosion on the circuits. In fact we took it in to have a couple outstanding recalls performed like REPROGRAMMING THE ECM, and replacing some exhaust components. Somehow they decided that the recalls had been open for so long, that it may have damaged the engine, so they put in a brand new engine and a some other parts that were not part of the recall. This cost us $0, and about ten days of waiting. We were really happy about this. Then we got the car back, first thing I did when we got home was to Roll it up on the ramps and open the hood, wow! It really was new. But, I noticed some of the unimportant parts were not bolted in at all, like the coolant reservoir and some big wire harness holders. Plus the lights in the stereo were no longer working and neither were the lights in the automatic shift knob. And even worse, the car would take forever to start every-other time you would start it to go somewhere, It would crank for 10 - 15 seconds before turning over. All these are signs of a faulty ECM. And of course now the dealership is denying any responsibility for the ECM. They say they only reprogrammed it and did not touch it. Today I noticed the A/C duct going to the ECM housing was disconnected, they were the last people to work on it and they worked on it a lot, but I cannot prove they accidentally disconnected that hose, although it could have been easily knocked off by someone replacing the engine. And they offered to fix it for $1,200. They said $900 of that was for the part. That's when I decided I would fix it myself and do it right for half that. I looked online and did not find the correct ECM anywhere, then I went to one of the other Nissan dealerships in town and bought it for $580.30 plus tax. Now they are saying they will fix it for $88. WTF?
  • edited October 2009
    You're Right! Thank you so much. Finding it was half the battle. everything said to look under the dash in the cabin.

    I took it in for the recalls, we were not eligible for the foam replacement one, but they did reprogram it. Now we have been having problems ever since. They also put in a some exhaust components and a whole new engine which surprised me because I thought it was running fine when we drove it there.

    She is not the original owner, she just bought it about four months ago from a sleaze bag of a salesman. The car has had 3 owners and the guy she bought it from makes a living by getting cars from auctions in the NY/NJ area and bringing them to our city on the gulf coast and selling them at blue book value. He was terrible to work with.

  • edited October 2009
    oh yeah, and the car has supposably about 111,000miles on it, but the dealership is convinced the guy we bought it from turned back the odometer to say it was under warranty (76,000miles) getting the new engine for free, then turning it back to it's approximate milage and not saying anything to us, all the while trying to sell it to other people for twice as much because the engine now has zero miles, when it was my idea to take it in for the recalls I found before we sign the bill of sale. wow. So we think it has about 111,000miles.
  • edited October 2009
    Thank you so much for your work. I tried a lot of things. I added what I found out to this thread. thank you. Thank you thank you.
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