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Discussion Starter · #1 ·
Hey all, recently picked up a 2003 350z with less than 100k miles clean title as a project car, the only issues are electrical. I have had it for a little over a week now and I am coming on here to see if anyone can give some advice. When I finally got power to the car (positive connection was broken that led to the fuse box) I turned the key and only got a few lights to come on i believe it was airbag, battery, and another i cant remember but no check engine but the headlights turned on and the radiator was on full blast. The car would not crank so I checked the clutch/brake buttons underneath and the rubber stops were broken off so i fixed that and still no crank. Checked that every fuse was fine and took out and checked the relay so that everything worked which it did. I even pulled out the ipdm and took it apart to check for broken solders which i couldnt find. fusible links are fine as well.

The last option I came to was the ecu could just be bad so when I took apart the passenger panel to reveal the ecu is when I came upon this absolute behemoth of disgust. Several wires unplugged with the ecu dangling by two zip ties! I cant seem to find anything to support me tracing all this wiring to where it is supposed to go so I was wondering if someone was able to send me a picture of how their ecu is setup and what wires go where it would be a huge help.

attached is the picture of the mess of wiring minus the ecu i took out
53268
 

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Welcome and here's a link to the NICO Nissan (including) 350Z FSM (factory service manuals) index:

Nissan Service Manuals - NICOclub

Go to the '03 model year and look at the back of the FSM for wiring diagrams of the ECM.

While you don't mention how much mileage, or what kind of obvious damage there was to this Z, I hope you got it for cheap. Electrical problems tend to be very difficult to track down and expensive to fix.
 

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Discussion Starter · #3 ·
Thankfully i got it for cheap from florida so clean solid body with a bit of aftermarket parts too. It’s just sad the previous owner really let this go. I believe i tracked down the main problem to the ignition switch and hopefully not the ecu, but i’ll definitely give that ecu wiring diagram a look at and see if i can’t piece this together!
Thanks!
 

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You're welcome and the FSM may also be able to help troubleshooting the ignition system. Do you have the ability to pull codes once the ECM gets rewired? The 350Z is heavily dependent on electronics and is typically very reliable once they are sorted. What color is your Z?
 

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Discussion Starter · #5 ·
You're welcome and the FSM may also be able to help troubleshooting the ignition system. Do you have the ability to pull codes once the ECM gets rewired? The 350Z is heavily dependent on electronics and is typically very reliable once they are sorted. What color is your Z?
I will give it a try to pull codes unfortunately i dont have any fancy obd scanners just the basic ones. Its a very nice pearl white with a carbon fiber hood (that has plastidip stuck to it :rolleyes:) and what looks like a nice duraflex sport bumper. no outside damage and has some nice tint film over the headlights and tail lights. Nice car seeing if i can get it running
 

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Your Z is likely painted in Pikes Peak White (color code QX1). Let us know how your repairs are going.
 

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Discussion Starter · #7 ·
got everything back together and pulled the ignition switch to test it and that works fine and gets the power to the fuses that need it. The only thing i have left is the ecm as the main problem. When i turn the key in the on position i get the same lights i mentioned previously even without the ECM connectors plugged in which leaves me to believe the ecu isnt getting power/doesnt have a good ground, or the ecu is fried. Im going to check the ecm relay again incase i overlooked it tomorrow or thursday and will update!
 

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Once you check your ECM relay, and reconnect the ECM, I'd consider using the OBD2 port for a code check via a code reader. If you can pull codes it may provide some clues as to whether it's active or damaged. If you cannot pull codes, or communicate with the ECM, you may have your answer.
 

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Discussion Starter · #10 ·
Its been 25*F and below with snow the past few weeks so i had to cover her up and wait a bit. I took the ecm apart and it looks clean no broken solders and no obvious circuit breaks. I called around and no one would look at or test the ecm without me bringing the whole car up so that really isnt an option. The entire harness is just a mess. Power is coming from the battery to the ignition switch and the ignition switch is sending it out however the other ends are not doing anything with it (not even ACC). I've been just studying the FSM and trying to piece something together why these arent getting power but no leads yet. I appreciate you following up.
 

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You're welcome! Have you tried pulling codes when the ECM is powered up? Even a basic code reader should be able to communicate with the ECM if the ignition switch is getting power. It makes sense to determine if the ECM is intact, or if a new one is the only way to fix it. Did the car ever run since you bought it? If not, how did you get it home?
 

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Discussion Starter · #12 ·
I'm getting a link error when trying to pull codes, which goes with the theory I've had that a lot of the car is just not getting power especially the ecu, if it was warmer I'd have no problem taking apart every trim piece and following the harness. The car has not ran since I've got it I haven't tried cranking it by hand or jumping the exciter wire for the starter yet either. Also, I used a full sized car trailer and towed it home myself.
 

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If your ECM cannot power up, you may want to inspect the IPDM (intelligent power distribution module) located behind the battery on the right side of the engine bay. I hope you bought this Z for a song, as you seem to have also purchased a TON of serious and expensive electronic problems. Read the FSM to understand how the IPDM routes power to the ECM, which allows it to communicate via the OBD2 plug. Unless you've got a heated garage, I suspect you've probably got a project car that will have to wait for the summer.
 

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Discussion Starter · #14 ·
haha thankfully I got the car for fairly cheap to where i have to spend about 3,000 for it to be not worth it. And you are right while I do have a heated garage, it is full with other projects. I’ve been looking at renting out a space at a heated garage at a car club my father and I am apart of but until then i’ll have to wait till it warms up to take apart all the harnesses and track down the issue.
 

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Discussion Starter · #15 ·
BIG UPDATE: had a small stretch of 45+ weather so i finally got the car under jack stands to crawl underneath and found the exciter wire for the starter ripped off which got me pretty excited haha... ha.. but i hooked up a starter button and had her cranking but the starter is turning real slow even after hooking up a big truck battery up.

The wiring everywhere is horrendous and this car has been molested to say the least.

Yet at last i’m back down to 30 degree weather so I will wait a few days before inspecting the wiring and the starter a bit more before purchasing a new one. Just excited to be getting somewhere. 👍
 

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Not sure where you live, but this sounds like a spring/summer project at best. Do you at least have a garage to work on it, or is this an outside project? I don't know how some former Z owners get to the point they try to rewire a difficult and complex wiring harness. Was there any history on this Z before you purchased it?
 

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Discussion Starter · #17 ·
Sadly all the garage spots are taken up by some classic cars so it’s an outside project for now. Managed to get the starter off to inspect it, works greats but the positive terminal was so loose on the starter that it might have been causing the issue. Also the male ended clip that plugs into the wiring harness from the starter is just gone so I have to figure out what to do about that.

It was supposed to be a spring/summer project but I was just too excited that I couldn’t wait so I try to come out for an hour or two in the cold weather just to get some stuff done before it warms up.

And you would think that a wiring harness that was researched and developed to try to be the best possible for the car should NOT be cut and hacked into but people just decide to do what they want I guess. I live in Ohio; Monday Tuesday and Wednesday we are supposed to have 55+ and clear so I’ll update!
 
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