I'm doing an S5 T2 swap into my N/A S4. I have the J spec wiring harness and Ecu. What does the third plug on the harness plug into?

Also does the harness that is behind the dash on the S4, plug into the S5 ECU or do I need to change the plugs?

Also what then plugs into the square box that is connected to the ECU?

 

If it makes anydifference I don't want A/C, P/S, or cruise

 

The difference between the S4 and S5 wiring harnesses/ECU is like the difference between chocolate and **** (haha bad amine reference). Lots of work has to be done to do a complete swap.

Do a search you will find a million topics about TII swaps.

Happy searching
- Dana "where's Icemark to lay the smack down today?"

 

I have done the S5 /S4 swap.

You realize that unless you use a S5 ECU you will NOT be running a OMP and will need to go premix.
Unles you swap front covers to S4 so you can use a mechanical OMP.

On my swap I used a S4 TII EFI harness.

I rewired about 4-5 wires total.

Everything else plugs in fine.

There were 2 yellow ECU plug on my harness and 2 orange ones with a smaller white 4 pin plug.

The 2 yellows go into the ECU.
Both orange plugs go into the main harness
The white plug goes into a atmosphere sensor in the kick panel.

Running AC/PS/ and Cruise will have nothing to do with the interior part of the EFI harnes.

The Cruise is a 4 or 6 pin plug near the windshield wiper plug on the firewall.

 

I am using a S5 ECU

Should I buy an S4 engine wiring harness to make this work?

 

Well S4 would probably be the easiest way.

It's a PITA to run with both S4 and S5 stuff.

Now. I know some one has done a rewiring of a S5 ecu and EFI to a S4 interior. try searching for that thread.

www.rotaryresurrection.com has a tch section with a series swap. read it.

I am running my S5 engine as if it were S4.
It has Mech OMP and S4 front cover.
S4 injectors inec they are different plugs(You can splice in S5 plugs into a high impedance S4 harness//88 engines have high imp)

The BAC will also have a different style plug.(oval for S5 and square for S4)

You will not have a functioning S5 boost solenoid this way but you can just get a boost controller to make up.

 

Oh yeah You'll need a S4 AFM as well.

 

since i have a jspec T2 front clip would it be eaiser to use all the wiring from the clip and put it into my car?