03-04 cobra conversion specialist- Looking for opinion on cobra harness differences

stang99svt

Enter something here
Established Member
Joined
Jul 18, 2003
Messages
1,929
Location
Michigan/Virginia
I figured I have an entire 03 cobra wiring harnesses through the whole vehicle EXCEPT, the wiring harness that connects the under the hood primary fuse box to the under dash. I've included a picture. My question is what is the difference between a 2003 GT wiring harness and a 03 cobra harness? I'm still chasing why the fuel pump won't engage....
s-l1600.jpg
 

hotcobra03

Well-Known Member
Established Member
Joined
Mar 11, 2007
Messages
7,461
Location
poteet,texas
Fuel injectors may be pinned differently

Best way is wiring diagram


Home

Here is link for 2 versions

Quick manual with some wiring that will work on cell

Than the main manual that only works on pc. Being the best.

Chilton Library

One 1 found for cell full version like pc
 

decipha

Well-Known Member
Established Member
Joined
Jul 12, 2008
Messages
1,019
Location
New Orleans, LA
you should never swap a cobra harness in to a vehicle when doing the cobra engine swap thats just a horrible idea and makes it significantly more time consuming and difficult than it needs to be

Keep the gt harness.

You will need to unpin the connector for the coils and flip the wires around. 4v coils are reverse polarity compared to the 2v coils. Same goes for the alternator just swap the wires around. The middle wire isn't needed if you have one. If you have the cobra alternator connector you will see the wires are swapped just simply keep the wiring colors the same.

You will need to cut the wires going to the iat sensor and extend and run them to the iat2 sensor. That's the sensor at the back of the lower intake.

The bypass actuator gets hooked up to manifold vac. The boost bypass solenoid is not used.

Most people hook up the intercooler pump relay so it comes on with key on / ignition. If you have an unused ecu output pin though you can wire it up to that and enable the ic pump and assign it to that pin in the tune.

There is no other wiring modifications needed. The GT wiring harness and ecu is otherwise the same as the cobra.

I just posted this yesterday in another thread https://www.svtperformance.com/threads/terminator-engine-swap-into-03-gt.1177683/
 

stang99svt

Enter something here
Established Member
Joined
Jul 18, 2003
Messages
1,929
Location
Michigan/Virginia
@decipha To validate the original post and your statement, the ONLY GT harness is the one in the picture. otherwise all other harness included the engine harness is from a 03 cobra with a 03 ECU.
So I'm unconfident why anything would need to be cut or spliced.
 

R3APER04GT

New Member
Joined
Dec 27, 2019
Messages
5
Location
Fort Worth, TX
So this is literally all that needs to be done? Just double checking because i will be doing a terminator swap in a few months. Also, i thought i read you offer a base tune?
 
Last edited:

stang99svt

Enter something here
Established Member
Joined
Jul 18, 2003
Messages
1,929
Location
Michigan/Virginia
Well I never got it working, spent a month. Bought some expensive wire probing gear. Pretty much gave up. I wasted more time in 3 weeks then if I had just worked and bought a used one with low miles.
 

HardknoxsTech

New Member
Joined
Mar 29, 2021
Messages
6
Location
St.Joseph
Well I never got it working, spent a month. Bought some expensive wire probing gear. Pretty much gave up. I wasted more time in 3 weeks then if I had just worked and bought a used one with low miles.

New member here. Just wondering where you ended up on this, if you ended up getting it done and where you found the problem to be if so.
 

R3APER04GT

New Member
Joined
Dec 27, 2019
Messages
5
Location
Fort Worth, TX
Hey Decipha, quick question. Will there be any issues with monitors in terms of smog check if swapping to the Terminator Motor and uploading the Tune for the GT computer. As long as i have all retaining emissions equip. (Cats..etc) + tune, will it be good?
 

Roush6018

Active Member
Established Member
Joined
Nov 9, 2008
Messages
106
Location
san jose,ca
Well to complete the swap and get the motor running is the goal. Then to pass the smog check is a whole second goal after getting it running. The computer just controls the fuel pumps and injectors and ignition coils, and o2 sensor and Evap controls, fan ETC. you have to get those parts wired right before driving the car.

so the smog check will see if your GT computer has a non OEM Ford tune to run your cobra motor. It will fail for the tune data not being OEM or “modified”.

The engine will run on the GT computer with tuning. I did my swap and took out the GT ECU and installed a 03 cobra ECU .

I am running a stock 03 cobra computer and all the monitors set to complete and pass the smog. All of the smog equipment is there too. My car is a 2001 roush with cobra swap.
 

Roush6018

Active Member
Established Member
Joined
Nov 9, 2008
Messages
106
Location
san jose,ca
I did have to swap some harness from GT to 03 cobra. The engine harness and transmission harness are 03 cobra specific. I also had to replace the Power Distribution harness, this has the power for the intercooler pump. I got my fuel pumps to run with the GT fuel pump harness, I ran a power wire from the battery to a BAP and into my FPDM.

I also had my car running with the GT dash harness, but I did have a problem with that. When matching up the wires in passenger foot well there were extra wires, I did match all same color wires up. My key would start my engine, Problem was when I turned the dash knob to defrost my engine would stall , turn off.
I removed my dash and installed a 03 cobra dash harness, I think it was for a vert, , my car is a coupe, and I matched up all the wires In passenger footwell. Then my engine started and ran good, turn on defrost and it still runs and turns on the defrost. And I can scan the computer with the OBD port.

my swap was done very long ago. But I am almost sure I replaced the PCM harness from GT over to 03 cobra because it has the 2 big green power wires needed for the fuel pumps. But, there is a chance that the 2 big green wires for the fuel pump come from the Power Distribution Harness. The 2 green wires I am talking about are located in passenger footwell near the PCM and they would be included in the 03 cobra fuel pump harness.
 

P49Y-CY

fomocomofo
Established Member
Joined
Jun 21, 2003
Messages
11,217
Location
southwest
couple years ago when i was chasing a fuel problem i got the factory wiring service manual and was surprised to find that there were important differences between the cobra wiring and all other v8's.

for example, the inertia switch is inline between the ccrm and fpdm on all v8's, except for the cobra where it has its own path to ground.
 

decipha

Well-Known Member
Established Member
Joined
Jul 12, 2008
Messages
1,019
Location
New Orleans, LA
Ive done several thousand 4v swaps and Ive never spent more than 30 min tops on wiring. Last one I did I drove in to the shop that morn, swapped the engine and owner picked it up all in the same day.

No probing needed.

Yep it will pass CA 50 state emissions perfectly fine.

The only way a custom tune fails emissions is if your using a commercial tuner such as sct or hptuners or if your tuner is incompetent.

GT and cobra ecu are the same class ecu so the tunes are interchangeable.

Just like the lightning engine swaps in to regular f150's I've never understood what compels people to try to swap wiring harnesses and even the dash and all adding all that extra time and effort when its not needed and there is absolutely ni benefit to it.
 

R3APER04GT

New Member
Joined
Dec 27, 2019
Messages
5
Location
Fort Worth, TX
Ive done several thousand 4v swaps and Ive never spent more than 30 min tops on wiring. Last one I did I drove in to the shop that morn, swapped the engine and owner picked it up all in the same day.

No probing needed.

Yep it will pass CA 50 state emissions perfectly fine.

The only way a custom tune fails emissions is if your using a commercial tuner such as sct or hptuners or if your tuner is incompetent.

GT and cobra ecu are the same class ecu so the tunes are interchangeable.

Just like the lightning engine swaps in to regular f150's I've never understood what compels people to try to swap wiring harnesses and even the dash and all adding all that extra time and effort when its not needed and there is absolutely ni benefit to it.

As always thanks for the info. Would you be interested in doing my Termi Swap? If so id like to contact you and speak more about it off line.
 

decipha

Well-Known Member
Established Member
Joined
Jul 12, 2008
Messages
1,019
Location
New Orleans, LA
We are about 3 months back logged at the shop right now but if your not in a hurry come drop her off. Dallas to New Orleans is about an 8 hour drive.

My cell is five oh four six oh six oh five three two
 

Users who are viewing this thread



Top