# 2009 NAH U0100 code



## Robertocarlos Loredo (Dec 3, 2018)

Hey guys new here. So I was driving down the highway when the car would now accelerate anymore, pulled it over and the car will not move. I looked up the problem and it looks like is somewhat common but there is no straight answer. I'm able to get 30 secs on EV mode by taking the negative cable off the 12V battery but that's about it, I read the code on the car and it reads U0100 so there is a loss of communication with the computer. The two major ways I read people fix it is replacing the 12V battery, and in some occasions that the ignition coil somehow creates this problem, So I will start with the battery and go from there, but does anyone know what causes the problem? I do not want to try 100 different things before taking it to a mechanic. :crying: any advice?


----------



## Robertocarlos Loredo (Dec 3, 2018)

Not a lot of help. I looked around, some people said the battery, changed it not it. some said coil that doesn't make sense butch changed them and plugs, nothing, fuses look ok, made a video so everyone can see. but it looks on this forum you can't post links, you can look up youtube for 2009 Nissan Altima hybrid won't start


----------



## oscarsierra69 (May 5, 2021)

Robertocarlos Loredo said:


> Not a lot of help. I looked around, some people said the battery, changed it not it. some said coil that doesn't make sense butch changed them and plugs, nothing, fuses look ok, made a video so everyone can see. but it looks on this forum you can't post links, you can look up youtube for 2009 Nissan Altima hybrid won't start


I know its been 2 years since your post, and I see no responses to it. I'm having this same issue with my 2008 altima hybrid. What was the issue and how did it get resolved? If you don't mind sharing.


----------



## VStar650CL (Nov 12, 2020)

U0100 generally means the ECM is offline. If the ECM fuse is good then the most likely culprit is a bad ECM relay (in the IPDM). If the ECM fuse is blowing then the most likely cause is a failed or failing spark coil that's melted internally. Look for "warts" on one or more of the coils.


----------



## oscarsierra69 (May 5, 2021)

VStar650CL said:


> U0100 generally means the ECM is offline. If the ECM fuse is good then the most likely culprit is a bad ECM relay (in the IPDM). If the ECM fuse is blowing then the most likely cause is a failed or failing spark coil that's melted internally. Look for "warts" on one or more of the coils.


Thank you. I appreciate the response. I had read that information on several other posts online. I was hoping the op would get a notification of my comment and respond with his specific fix. Since its known there are several possibilities with this error on the NAH. Some inexpensive, some not. Was just curious.


----------



## VStar650CL (Nov 12, 2020)

The ones I described are by far the most common, and neither one is terribly expensive to fix. The relays are about $20 even at the dealer, and aftermarket coils for the QR platform are available all over the place. Check the fuse first, that will immediately tell you which tree to bark up. Don't check visually, use a test lamp (a visual check won't tell you if the ECM fuse has no power, which will mostly likely mean a bad fusible link further upstream). If the fuse is blown, take all 4 coil connectors loose and replace the fuse, then see if the car tries to crank the engine. If it does, one of the coils is shorting. If the fuse is good, there's a very great chance that the ECM relay has gone south. I can't recall if the ECM relay is exposed on the hybrids or buried in the IPDM, but you can check by swapping the two exposed relays and see if it starts. If not, the hybrids use the same IPDM's as some Infinitis, so used ones aren't hard to find for under $100 by searching the Nissan part number.


----------



## oscarsierra69 (May 5, 2021)

VStar650CL said:


> The ones I described are by far the most common, and neither one is terribly expensive to fix. The relays are about $20 even at the dealer, and aftermarket coils for the QR platform are available all over the place. Check the fuse first, that will immediately tell you which tree to bark up. Don't check visually, use a test lamp (a visual check won't tell you if the ECM fuse has no power, which will mostly likely mean a bad fusible link further upstream). If the fuse is blown, take all 4 coil connectors loose and replace the fuse, then see if the car tries to crank the engine. If it does, one of the coils is shorting. If the fuse is good, there's a very great chance that the ECM relay has gone south. I can't recall if the ECM relay is exposed on the hybrids or buried in the IPDM, but you can check by swapping the two exposed relays and see if it starts. If not, the hybrids use the same IPDM's as some Infinitis, so used ones aren't hard to find for under $100 by searching the Nissan part number.


Thank you for this! I really appreciate it! This is what I was looking for.


----------



## VStar650CL (Nov 12, 2020)

You're most welcome, happy to help.


----------

