2005 Pathfinder Code U1000 Brain Buster

[Luscombe8apilot]

Hello all, I have a major headache from this u1000 code. I have found little info on how to diagnose this problem. Most of what I found says bad ground somewhere and I have checked all of them that I could find, although I'm sure I've missed some. Does anybody know where to find a good diagnostic procedure for this issue. When I turn the ignition on my dash lights flash on and off and the cooling fan turns on and off, there is no P or N in the gear display, the engine turns over but won't start. When I put it in reverse or drive,3,2,1 it shows the gear in the display, the fan shuts off the dash lights settle down. This really bogles me, really need some help. Any help greatly appreciated!!

[Towncivilian]

U1000 is an error in the CAN communication line. The factory service manual has next to no info about diagnosis. I'd assume to check the specific wires for the CANBUS leading from the ECM. Page EC-168 of the factory service manual has a wiring diagram - looks like it's only two wires, so if you are able to inspect them then do so.

I would check for TSBs on this subject but my Chilton online link expired months ago, sorry! It may be best to have the dealer fix this specific issue, unfortunately.

[Luscombe8apilot]

U1000 is an error in the CAN communication line. The factory service manual has next to no info about diagnosis. I'd assume to check the specific wires for the CANBUS leading from the ECM. Page EC-168 of the factory service manual has a wiring diagram - looks like it's only two wires, so if you are able to inspect them then do so.

I would check for TSBs on this subject but my Chilton online link expired months ago, sorry! It may be best to have the dealer fix this specific issue, unfortunately.

Thanks for the reply, I am new to the forum and appreciate any and all help with this issue. I have searched alot of places on the internet and this place has been the best as far as information goes. I now have about 1,400 pages of service manual printed and will start checking harness connections and grounds more accuratly today. From the look of things you have to have a masters degree in nissan service to understand this manual, but i'm learning. I wanna add that I had to replace a TCC spool and solinoid in the trans due to torque converter shutter about 10 days pryor to this incident but that seemed to go very well with no problem so I'm not sure if it's related. I'm going to check it out anyway. I've seen alot of bad stuff about the IDPM also so I tried the relay swap and it started once, drove for about 10 min with dash lights still going crazy in park and neutral and now it won't start again, codes u1000 and p0462 can and fuel. Thanx again and any help is appreciated. Will update as I go forward with this.

[Luscombe8apilot]

Update: Well after reading ALOT and learning to understand the wiring harness diagrams and schematics in the service manual, I have managed to mess around with the Ipdm and Ecm enough to lose power to the Ecm. Then it wouldn't start, my ses light would not come on at all and my obd2 code reader would not link. I checked the ecm relay on the Ipdm and it was good so I checked for voltage at Ecm and I was not getting ignition power from the Ipdm. I jumped the relay curcuit at the Ipdm and what do ya know, it started right up. Headlights and radiator fan are still coming on and off and after I shut it off it would not start back up. I checked codes with my obd2 and got u1000 and p0462 again. I checked power from the Ipdm to fuel pump and it would not cycle. After about 5 times of trying to start it finaly it did. I am going to break down and gamble on a $400 Ipdm from the Nissan stealership and see if that helps.I don't know if that will fix all of my problems but I'm pretty sure it's bad. If anyone has any ideas or info please let me know. Either way I will I will keep posting till I get it or give up. Thanks

[Towncivilian]

Isn't the IPDM just a relay? I really don't know too much about the newer CANBUS based systems, I apologize. I hope you'll be able to solve your problems without some expensive dealer diagnostics.

[Luscombe8apilot]

The IPDM is intelegent power distribution module, it's the box under the hood over the pasenger wheel well full of fuses and relays and controls alot of different stuff. I replaced the whole thing with new fuses and relays and it did not fix, still no power to the ecm. I jumped the ecm relay on the ipdm and drove it to the dealership and they are as confused as I am. They said they need more time to diagnose, at $95 an hour this could be expensive. I will let you know what I find out. Thanx for the replys.

[Luscombe8apilot]

Update: Well apparently the ecm has to tell the ipdm to turn on the ecm. The tech at Nissan told me he checked several things and he thought the ecm was bad, didn't make much sense to me but I went along with it. I ordered a ecm on ebay and put it in myself yesterday at nissan and now when I turn the key on my check engine light comes on and I can link my obd2 code reader to the ecm which I couldn't do before, and there were no flashing lights and radiator fan coming on and off like before. Now I'm waiting for the tech to reprogram the keys to the ecm and reset the NATS so we can see if I have any other issues. Hopefully this is coming to a close. Wish me luck!!

[Luscombe8apilot]

So the tech programed the keys to the ecm, said it started up, ran fine and when he shut it off and tryed to start it up again it would not start. He said the nats was tripped so he reprogramed the keys and it started again and ran fine but when he shut it off same thing happened and it wouldn't start. He said it was not saving the key program for some reason and he needed more time to look at it. That was 6 days ago and I haven't heard anything else from him. This is realy getting frustrating!!

[Luscombe8apilot]

update: So finaly got the path fixed. I replaced the ecm again and the tech programed the keys and BAM everything is back to normal. So I have to say thanks to the guys down at Lynn Layton Nissan in Decatur AL for helping me out and not breaking my wallet. That was first experiance at a shop and in my opinion they were more than fair. I guess I've learned that there are some things you just have to have the right equipment to get the job done. I could have saved myself about $400 if I had'nt been to stuborn to just take it to the shop! Anyways maybe these posts will be helpful to someone in the future but I realy felt I needed to post the end results as alot of times other people don't.

[Towncivilian]

I'm glad to hear you've finally got the problem solved! It's rare for ECMs to go bad, but your experience shows that it's not impossible.

[Luscombe8apilot]

Thanks for the replies towncivilian!

[Luscombe8apilot]

Well, I thought we had it fixed. Unfortunatly the coolant had been in the transmission and the problem returned. I took it back to the Nissan service department and a month later they gave up and said I probably need a transmission. The mechanic said that nissan engineering of america told him that it could be the TCM but they have no way to prove it so we got it to start and I drove it home, "no shop charge". I guess he felt bad for me. I removed the valve body and took apart the TCM and it was covered in sludge all over the electronics. I cleaned it off, put it back together and bypassed the radiator and it is back running again. So I guess the TCM can also make your car go crazy, even though when it did run you could drive it and it would shift just fine with no transmission codes but in park or neutral it would go crazy and when you shut it off it might not start back. I don't know how to post pics but I have one of the TCM with the sludge on it. Also if anyone atempts to remove the TCM from the valve body you must be very careful not to break the solinoids and do not mix them up. I hope this helps someone. Also there is a video on youtube on (saving the RE5R05A TCM) very good video. Thanks, just thought I would share my results as I know it is annoying when nobody posts the final fix.

[Slumpert]

Gah so many bad stories of those radiators failing like that......

[Towncivilian]

Yeah, that's very unfortunate that such an issue exists and that it is spread across many model years and vehicles. It's good that Nissan extended the warranty, though based on your DIY fix it sounds like perhaps you weren't covered by it, Luscombe8apilot? Since coolant and transmission fluid have been mixing, there has almost certainly been damage to other internal components of the transmission. I don't know what to suggest - did Nissan say that you weren't covered by the radiator warranty extension?

[Luscombe8apilot]

Unfortunately I'm not covered because I have over 100,000 miles. I believe that this was a temporary fix so I have decided to have the trans rebuilt with a new valve body, TCM, Sol's, torque converter, all steel plates and bushings and all new rubber parts. Complete rebuild at a reputable shop with 12,000 mile warranty for $3500. They pull it, build it and put it back in. I have the radiator bypassed and plan to add an extra external cooler to run in series with the factory one so it should stay cool even when towing. The tech at the trans shop says he has dealt with this before and said that by the time you find out the fluid has been there, most of the damage is done. The TCM repair seems to have helped my can problem but I am afraid I'm on borrowed time with the rest of the trans so I dropped it off today to be rebuilt.

[Luscombe8apilot]

Well transmission has been rebuilt. So far we have about 1000 miles on it with no more issues so maybe this time we got it. Its hard to believe all this headache was from coolant in the transmission. Nissan realy needs to do something about this, I know there are many cases of this happening and it's very costly.

[unreal2k1]

I have also had this issue and it turned out that after the trans rebuild an aftermarket cooler was installed that was to small and eventually burnt the oil and after a flush caused the u1000 code to come up and 2 months later and a couple of thousand dollars spent on parts that was not the problem it turned out to be insufficient cooling. the factory air cooler was also bypassed which was dumb and now its flushed out valve reversed to allow fluid thru from the start and not when its hot and tandem to a low pressure drop cooler all synthetic oil flushed again and now trans does not go above 175 with load and stays at 165 under normal warm weather driving. Anyway the fix was the cooler not being big enough and its amazing how little some trans rebuild shops and or dealers know about the cars we all drive. Just thought I would post this since I spent months doing looking up my U1000 code and none of the fixes out there helped. Even had the car for a month at a dealership and changes out things that did not need to be changed all electrical so nothing could be returned.

[unreal2k1]

Luscombe8apilot make sure that your coolers are hooked up the right way and if the radiator is bypassed like they told you check to make sure the factory cooler on the right side of the radiator which is for the trans is in tandem to the other cooler they installed?

[GrjAZ]

Hi I have a 05 also. Your thread is helpful because its the 1st I have read that states the issues of my vehicle could really be the TCM not ECM. But I am curious when diagnostics was ran did yours show lots of different codes? Because as far as symptoms mine are the same to where now I noticed it happens mostly in Park. Its now at Nissan for the 3rd time & been there since Fri. They were going to try an ECM & call me back. Not till Tues aftrnoon did they finally have an answer. They said I need a whole new transmission but didnt even have a price for me. The first time I took my vehicle when it started stalling & all the lights started going off it costs $400 & they said it was my sensors. Then the 2nd "my key had reset itself but no answer as to why". At that time since Im a used car owner I researched myself & found out there was a recall. I was upset they didnt inform me or tell me that it could be a major issue if not addressed. They said it wasnt anything that would cause my car to not start & that maybe my battery cable needed replacement but the were not sure. Then it was just the key & Maybe it was old &I should buy a 2nd" not more than 2 weeks later My car is locked up & wont start once again.

When I asked what would have caused the whole transmission the need to be replaced they got upset & more upset when I asked did you try the ECM from another Pathfinder like u said you were (they brought up not me). The manager was upset said they weren't going to do that & it burn. Then they said I hadn't been honest & Its my fault for buying the car where I did. And that me taking it for service to other people was an issue. I was FURIOUS because I have only had it have oil changes elsewhere. The 1st stalling issue I took it straight to them & it only worked for maybe a month after. The 2nd time yes I had someone else try to get me a diagnostic but too many error codes came up. So took it back to Nissan where they said the same thing there's too many error codes. Now they even brought up I'm lying its been in a wreck since I had it. Which was wrong technically I had another touch me from the rear. I did not have a scratch or any repairs. I only reported the hit because the other car because it hit & ran. It sped off all crazy almost hitting elementary kids who were being released from school 1 being my kid. I didnt care that my car had no visual damage or anything but I was upset kids could get hurt. But when that happened my car was STILL working with no issues. So how can that incident from Jan have anything to do with July or now? Sorry long post but I feel jipped by my service & want others feedback please. I owe too much on my vehicle I want it working again

[GrjAZ]

Sorry for the typos also. Im posting from my phone