I want to find the best way to upgrade to the new style ecu so that I can get it tuned. What is the easiest or best way to get this done? Any help would be much appreciated.

 

Technically since the wiring is all the same just different harness and pinouts you could probably pick-n-pull the ECM and main harness from a suitable donor vehicle and just splice the entire thing.

You will then need to have the ECM matched to the BCM and keys so the car will start, typically you would tow to Nissan and pay them to do it but you can do it yourself if you're computer savvy enough to navigate through Nissan Datascan II on a laptop connected to the vehicle, you will need to decode the BCM with an online tool so you have the PIN number for it.

Unless you have some serious sentimental attachment to the vehicle it would be a lot easier to just buy another G35 and sell the one you have.

 

So I could do this my self but would it be easier to get a stand alone ecu or piggyback system. I am kind of attached to this car I just rebuilt the motor with forged pistons and rods arp studded crank and heads looking to go turbo but the more I read about it no one offers tuning software for the old ecu.

 

Depends on how much HP you are shooting for. My 02' G20 uses the same generation ECU and processor and runs 20psi boost with a piggyback just fine. If you are joining the 450+ hp club I would think about a standalone.

 

Looking to hear from someone who has done this. How did it work out how much time and money etc? Which system did you use? If I took my car to a dyno tuner would they be able to work with my stock ecu?

 

Sell it and get a newer one

 

I’ve had this car for ten years and I love it. It started burning oil pretty bad and I decided to fix it rather than buy another used car with someone else’s problems. I am a master tech and have been working on cars for 20 years now as a profession. I spent about 4 gs on it between the machine shop and other things it needed to get it running and driving peek again. I don’t want another car I want to make this one bad ***.

 

It's not what you want to hear, but you should have researched this before investing in the early ECU model. Here's a very long thread that you can read to better understand why folks are telling you to sell and replace if you want to go FI.

https://g35driver.com/forums/showthr...=339467&page=1

 

Since it looks like you will probably be taking the long and difficult route for this because of sentimental value I STRONGLY recommend finding a wrecked vehicle (intact so everything is still hooked up but preferrably with a blown motor so it's cheaper) with the newer ECM and start swapping everything over.

That way you have a completely functional (but wrecked) donor you can put side-by-side with your vehicle, remove components from your vehicle and throw them in a junk pile, remove the same component from the donor vehicle and put it on your vehicle. It will probably only take about 40 hours of work to complete the entire project.

You should be able to find a suitable donor for under $1k, when everything is swapped and your car is running again take the pile of old components, toss them in the back seat and have the vehicle towed back to salvage.

 

So the truth is I am pretty sentimental about this car. I have two daughters and the time it was the best option for me cause I needed a good back seat. This car has prove fun and reliable for the most part. My wife actually agreed to let me rebuild this car and get it painted and turbo and etc. make it what I want. I have a 400 a month budget for this thing like a car note. I have been trying to get it ready for track and turbos from the ground up. I know that it is a major project and I am ok with that.
The only question I have at this point is if I get the harness and module out of an 04 would I have to do anything else beside programming anti theft?

 

There newer ECM is set up to drive dual electric fans so you would need to delete the 1 mechanical fan you have, use the pulley off the newer motor so it's just basically another idler (that's how the newer ones are set from the factory). The harness will include the two electrical connectors for the newer style dual electric fan setup.

You will also need to swap the IPDM I think since it's got fan relays for driving that setup in a high/low configuration but that's all part of the electrical harness as well.

If yours is equipped with the 5AT tranny you will probably also need the transmission valve body, TCM, and wiring from the donor. Your vehicle will have an external TCM mounted right next to the ECM while the donor will likely have the internal TCM mounted on the back of the valve body. It's all replaced as a unit fortunately, drop the transmission pan, unplug the harness, unbolt the valve body, take the wiring harness grommet out (snap ring from the top) and reinstall the new stuff. Newer harness will be used from the donor car because your transmission harness is 3 green plugs whereas the newer one is a single large connector on the transmission. The housing is completely interchangeable and everything else in your transmission will work normally, they're both RE5R05A transmission it just went through a series of revisions and one of them was to relocate the TCM into the transmission itself. Google search for the "transgo shift kit" and you'll have good instructions on how to remove the valve body.

I can't think of anything else right off hand, the BCM should just plug/play so that's a non-issue.

You will definitely want a donor that has the same chassis configuration as you though, so if you have a sunroof you want one that also has a sunroof, etc. If yours is AWD you want a donor that's AWD.

Personally I still think you'll be better off finding a donor and just swapping your motor over into that chassis along with whatever other components are in better condition/upgrades and then just selling off the chassis you have currently. It would be significantly less work for sure.

You would also have the option of getting into a coupe if that's something you're interested in, 2003-2004 coupes with 5AT or 6MT used the same engine, 2005-2007 used the same engine if they were equipped with the 5AT.

 

You could probably find a nice clean newer chassis with a blown engine for about $1500

 

I didn’t realize I would also have to get in the tranny. Seems like they made some pretty drastic changes just between the 03 and 04. Anyway finding a good clean 04 or 05 to do a motor swap might be an option, but I don’t think I will have much luck with that either.
How about it! Anyone with 04 or newer G in the Houston area with a clean body wanting to sell for cheap?