3800 swap harnesses (Page 1/20)
I am finally caught up on my harnes building so first my appologies to those who have had to wait all harnesses will be going out first thing Monday morning. Second is I made a promise a while ago to do a build thread on a 3800SC swap harness and I now finally have the time to do it.
What I would like to do is have some input on what options to run on this harness for example is it for a manual or auto swap and should emissions be kept or removed. I ask this because this harness is an extra that will be auctioned off when finished and all the money going to PFF the purchaser will need to pay Cliff not me. Not quite sure how to auction it off so a little help there would be appreciated.
The harness build first remove the complete engine harness from the donor 3800SC engine. I have hooks on my garage door that I use to hang harnesses on for stripping.

Next is to remove all the loom and tape from the harness, you will find on some that the wires all stick together which will require some extra work to pull them all apart.

These are a few connectors from the harness that can be cut off to free up the wires, they are the main firewall connector and the connectors for the ABS sensors and others for feeding wires into the car.

Next I remove carefully each pin from both PCM connectors, this is done by first removing the plastic covers then gently bending back the clip above the pin and lift the pin slightly then pull the pin back out of the connector by the wire.

With all the pins removed from the PCM connector I now seperate all the wiring from the harness and set aside each sensor connector with its wiring.

And of course save all the removed loom for sealing up the harness once assembled. A good idea is to go to a wreckers and remove extra loom from other cars as you will need more loom to finish off the harness.

Now I will pull out one of my spare engines to start reassembling the harness. At this point input would be nice on which tranny to make this harness up for the 4T65E HD that comes with the 3800SC engine or one of the manual trannies that come with the Fiero. Dan


Signature compliments of F-I-E-R-O
2003 3800SC series II powered

BoostedSeries1 NOV 17, 11:45 AM
I would like to see it done with a manual tranny. If that will be the one chosen I would say to make it for the getrag. Though it would not be much diff. for the other manuals
FastFieros NOV 17, 12:53 PM
I would say do an automatic, and then along the way make **NOTE** remove this plug for manual... Change VSS here to longer for VSS on GETRAG.. like that...

multmigs NOV 17, 01:19 PM
I've looked at alot of swaps and I vote for the 4t65eHD that's the trans it mostly came with and seems like it would be more complicated than doing a manual trans...
Auto it will be then, now to bolt up one of my 4T65E HD trannies to an engine and get wiring. Dan
chrisgtp NOV 17, 07:31 PM
I will offer to take the harness and pay cliff I was going to buy one from you any way but i dont need the extra emission stuff but it will not kill me if its there
A little more progress I have inspected and repaired any bad spots on the wiring and started to reassemble the harness on the engine.
This is the wires for the trunk side which includes the EGR, O2 number 1, MAP sensor and injectors 6,4and 2.

Now the firewall side which is the ignition module connector, the boost bypass solenoid and injectors 5,3 and 1.

Now for the trunk side again with the wires all taped up and the wires from the speed sensor, oil pressure sensor and the knock sensor added on from below as well as the alternator wiring made long enough to reach either the stock location or down lower on this side.

Now for the tranny wiring which includes the main tranny electrical connector as well as the neutral start switch, reverse lights and gear selection switch.

Now time to start combining the different portions of the harness together along with the wiring from the starter, oil level sensor, knock sensor and the A/C compressor clutch. I run the wires from the trunk side under the supercharger to clean things up a bit. Also joined in is the wiring from the throttle body which is the MAF, IAC, TPS and IAT. I find this is a good location for joining all the portions together to feed off to the PCM which on this harness will be mounted in the stock Fiero location.

2002z28ssconv NOV 18, 11:03 PM
If only you could have more than one "+"...
goatnipples2002 NOV 19, 12:27 AM
Thanks alot.
RideZiLightning NOV 19, 05:00 AM

Does everyone else do theirs like this? I have always just taken the loom off a couple sections, lengthened and moved some stuff around and re-wrapped it.