Basically it's like this, I have an 86 gt manual wiring harness from a junkyard, a 93 3.4 dohc engine with the harness cut at the engine and the 93 ecm. What I need to know at this point is do I need to find a complete 3.4 harness or is what I have enough to make it all work?

Make sure you differentiate between the 3.4 push rod motor and the 3400 dohc. They are very different, and I assume the harness is too.

I'm sure they are, Because, why not. Lol. A friend of mine just told me about a yard with the harness so I guess I'll pick it up just incase.

Some people graft the 2 together and some build new. I mocked up my engine, transaxle and firewall and put all of the sensors and connectors where they were supposed to be and made my end to end connections with wire scavenged from the 2 harnesses and a couple of other junk ones. I solder spliced and shrink sleeved mine together, others have depinned and repinned the connectors to avoid splices.

ltlfrari has excellent 3.4 DOHC harness information on his site. I used his info and got mine right on the first try.

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1986 SE Aero coupe.

3.4 DOHC swap is complete and running, now just have to finish the rest of the car...

With your 3.4 dohc harness cut, many of the wires will not be long enough, so if you use it you should plan to splice/solder and extend the wires.

If you start with a complete 3.4 TDC harness, then you can label and depin the wires at the ecm and connect each sensor to the engine 1 at a time and build a new custom fit harness. You will be left with most wires being too long, so you can cut then and crimp on new ecm terminal pins. This method is rather labor intensive, but the end result usually is much more visually appealing, especially if you focus on routing the harness through less visible areas.

The wires for the starter, alternator, and all gauges are in both the Fiero and 3.4 dohc harness, but the fiero harness has the right 500 and 203 connector ends so most strip down the Fiero harness to these basic circuits and integrate them into the 3.4 dohc harness, while removing any unused wires in the 3.4 dohc harness - this allows the harness to have as few wires in it as possible and reduce the overall bulk.

[This message has been edited by fieroguru (edited 02-18-2017).]

Another tip:

If your C500 is trashed (many are), there is a connector up front (C100, I think it's called) by the master cylinder that is physically identical. Most of the time these are in great shape because they are better protected from the elements and not subjected to heat.

Great info guys. I think I will try to get a complete dohc harness, it sounds like it will be the better route to go.

I was able to wrestle the dohc harness from the donor with minimal cutting. I believe I lost the air temp, map knock sensor and some of the alternator terminals.
I started to de loom and mark the harness last night. As I side note steam makes the job effortless. The tape nearly falls off.
When it comes time to repin the 93 ecm for the 92 harness and swap it to manual what tool will de-pin the weather pak style ecm?