Recently I replaced the motor in my 6MT 2003 350z, I also swapped a cd009 into it before doing the engine swap. I bought a good jdm low mile motor (automatic) and swapped my psp and ac into it. I kept my original wiring harness and used that, replaced both cam and crank sensors on the new motor. After getting everything in when I went to start it up the radiator fans kick on and goes into a "Fail Safe" mode. This also is keeping the fuel pump from priming, and the coils from sparking. Car will crank but not start. Originally we dove into the forums and found common issues with IDPM Boards and the relays, every relay, fuse, fusible link, BCM, etc is all good and has continuity. Nonetheless I replaced the IDPM board with an eBay one in excellent condition, problem still occurs. I pulled out the entire wiring harness and inspected for any shorts or breaks on the wires, all was good. I assumed maybe I cooked my ECM and that's why it was not communicating. Replaced ECM with exact spec replacement from my year and model car. Nothing. Spoke with the techs at Z1 Motorsports and they told me my wiring harness would be the culprit. So I once again removed it and replaced it with the exact same spec. Once all hooked up, still nothing. Fuel pump primes if you run a different power source, that isn't the culprit. All my grounds are intact, clean, and tight. Battery is fully charged. All testing has resumed with the original factory ECM, still it is not communicating. OBDII does not connect due to ECM not communicating. The car ran and had no electrical issue before replacing the motor. Any advice or suggestions appreciated, this is my first post on this forum. All wires and connections on the harness are accounted for and plugged into their correct spot.

 

Did nobody reply to this question? I'm going through the exact same thing and can't figure it out either.

 

Need to start with the basics.

Get a wiring diagram from the FSM.

Check +12V and GRND to ECU, there will most likely be more than 1 power and ground wire, need to check them all. Make sure each wire is clean, not shorted.
Note: Power is sent to ECU with ignition switch in pre-start location.

If it's not getting power, you won't get comms. If you can confirm you have good power and ground to the ECU, then you either have a fried ECU or a shorted CAN communication line that's bringing down the network. A good quality scan tool can check other computer modules like the BCM. If those are able to communicate, then that simplifies the troubleshooting.

If this sounds overly complicated to do yourself, take it to a professional with wiring diagnostic experience.

Good Luck!
-Icer

 

Here's an idea of how you go about checking PWR and GRND.

 

Have pulled the wiring diagram and I have a full shop. We had half a dozen people around a round table with printouts of the diagram before we dove back into it. Only thing I'm missing is any tuning software. Z1 referred me to Nissan to get the TCM and ECM reprogramed. We have done all of the diags you recommended but months ago. There is 0 shorts in the line and the ECM gets power through the harness. It just doesn't communicate and the ECM is not fried, neither is the BCM. Thanks tho? I guess lmfao. Guess you felt the need to include generic *** videos.

 

I apologize for my harshness. I must've misunderstood. The swapped ECM was one with a matching code on the back. I only used that ECM to test if mine was cooked and it was a relatively cheap try from a local. We did go through every electrical connection on the wiring harness and pin outs on the main connector. The ones that were supposed to get power, did. I still checked for short somewhere so I removed the harness and checked every single wire and connection and made sure no issues. All using the FSM's and correct paperwork. I did not mean Uprev, but yes the factory programming software. Ive tried reaching out to Nissan, but figured they just give the car to some run of the mill B tech and hope he can figure it out. Plus, it's a fairly modified street car that wouldn't be too friendly on the dealer tech. At this point I think a standalone setup would be more help. I don't have too much info on it, but Ive seen tons of other people convert so it couldn't be that hard. Maybe expensive?

 

The video I linked may not be for a 350Z, but it illustrates the process to follow on any vehicle for checking power and ground to a ECM. Your original post didn't have this level of detail mentioned, only that you checked main power and grounds, replaced the harness, swapped ECM, and replaced the IPDM.

If the swapped ECM was a "blank" then YES, Z1 is correct and you will have to take it to a dealer to have it programmed. I'm not sure what you mean by "tuning software" typically this means an aftermarket ROM reflash, like Uprev. But if you mean "programming software" then that would be Consult III Plus from Nissan/Dealer. The software and hardware required to flash a stock ROM onto a blank computer module is not cheap. I've looked into it myself.

Sure call me a clown, but apparently your round table of experts is not able to solve this one, even after you've been consulting techs at Z1. So shame on me for trying to help.
Good Luck with that.
-Icer

 

I'm going through the exact same thing and can't figure it out either.