What?! Why the hell would you think a starter when the engine is turning over and cranking like normal? That is like saying your A/C blows warm air but you're going to change the blower motor.

 

His problem is the car won't start on occasion. Don't you think there is the remote possibility it is the starter? The starter is probably responsible for 30-40% of all starting problems. The ECU probably 1-2%. I would put my money on the starter.

A starter often gets weak before it gives out totally. Just weak enough to not turn the engine fast enough to start on occasion. I had this happen to me. The starter lasted two months before it gave out totally. Until it failed almost completely it appeared to crank just fine. If it cranks a bit too weakly the car will not start.

The starter is easy to change and easily returned if it does not cure the problem. I'm not saying the starter is defintley the problem. From the comments made by the OP more than likely it is fine. But considering he is having a starting issue I would surely get it tested or try a new one before replacing an ECU. Actually unless I was sure the ECU was bad I would avoid changing it altogether. That would be the last thing on my list. It may end up that his ECU is bad but I would try and eliminate other possible causes first.


If there is one thing I learned when troubleshooting it is to have an open mind. Often times what appears to be a complex problem ends up having a simple solution. The problem is often not what it may appear. When you are really unsure about the cause of a problem eliminate the cheap and easy stuff first. You may save yourself a lot of time, money and grief.

I am not trying to lead the OP astray, I am just trying to help him solve the problem. I do not want him to go through the hassle and expense of changing the ECU only to find out it is not the cause of the problem. At this point even the "pros" at Nissan have not solved it. So I am putting in my 2 cents worth. If the OP chooses to ignore my advice I'm fine with that.

 

It's starting and running fine now. I have ordered, and should receive today, a salvaged ECM. The reason I'm doing this is that after we unhooked the front motor mount (which was confirmed by the dealership to have a short, and was causing the initial problem by tripping the security immobilizer NATS system), the car started and ran fine for a few days, then went into security immobilized mode again. I got it home, and got the security system reset by turning the ignition from off to on three times. Since then it's been fine, and i also unhooked the rear motor mount sensor to avoid another short. BUT - I'm concerned that the shorts have done some damage to the ECM, making it more prone to failure, or tripping of the NATS. The replacement ECM was <$100, it's a DIY drop in, and all that's needed then is to have the dealer or an auto locksmith with the right equipment reset the codes to work with my keys. After that, I have much more peace of mind that my kid isn't going to get stranded somewhere.

Thanks all for all the suggestions!