Can I slap a 2005 ECU and engine harness on my 04 Z? I'm struggling to identify the 2004.5 ECUs online so I figured going with 05 might be easier.

 

Why are you trying to change out the ECM and engine harness on your Z? Nissan makes small changes on the production line each year, so it's hard to know if these parts are a match.

 

What DK said -

Nissan made changes with the O2 sensors and other changes in the IPDM beween 2004 and 2005 (let alone the 2006 rev-up model).

You’ll want to know if the 2005 model was a RevUp engine or a standard DE and if it had wideband o2 sensors or narrow band (likely wideband)…and did your car come with widebands?

Usually ECUs are compatible between the DEs regardless of years but the RevUp ECU will not work on a DE. From my experience and understanding it does not matter if the ECU came from an automatic or a manual transmission car.

Further, plan on paying nissan or a automotive electrical technician to reprogram the keys, ECU/NATS, and the BCM - these will not be compatible with each out whatsoever.

 

Yes you can use a 2005 ECU and keep your current harness. We will have to flash the ECU with Uprev to bypass NATS (immobilizer) which will save you an expensive trip to the dealership.

Ideally get one that matches your current setup (DE vs revup, MT vs 5AT) but if not we can correct all that with the Uprev tune as well.

 

Its mostly this easy … but a 2005 ECU that came from a car that had wideband o2 sensors will not work with a 2003/4/5 that has narrow band sensors. There are some small difference in the wiring that will derail your progress.

MT vs. 5AT doesnt matter

 

Yes, narrowband vs wideband is very important as well