LS4 ENGINE WIRING (Page 2/2) Will JAN 22, 10:01 AM quote Originally posted by Dennis LaGrua: One wire from engine to PCM can go in only one place. If you are talking about a swap harness many of the wires are already connected. On a basic harness you just need to change maybe 15 wire connections to get everything to work. On my first 3800SC harness we only had to make about a dozen changes as we retained the GTP power center. It wasn't that hard and it took only one evening. quote Originally posted by qwikgta: Since I have built a few harness, I can tell you that once you get all the pinouts, and all the wire diagrams for your motor and the stock Fiero, its not that bad. What folks don't understand is that the engine harness is already done. From the PCM to the sensor, its not changed. For the most part, (95%) you don't touch the engine harness, its the portion of the harness that leads into the cabin and connects to the Fiero harness. Some swaps have the fuze box in the engine bay, in the Fiero its under the dash. What your doing is connecting the wire from the swap to the same location in the Fiero. In the end its usually only 15-20 wires that you need to "fix". Rob Very much depends on how neat you want the finished harness to look. If you're putting a lot of effort into making the swap look neat, then you're going to want to build the harness wire-by-wire in order to get the routing and lengths of all the wires "right". Just like everything else... if you don't care how neat it is, you can do it quickly and cheaply. fieroguru JAN 22, 07:39 PM quote Originally posted by Will: Very much depends on how neat you want the finished harness to look. If you're putting a lot of effort into making the swap look neat, then you're going to want to build the harness wire-by-wire in order to get the routing and lengths of all the wires "right". X2 qwikgta JAN 23, 05:44 PM quote Originally posted by Will: Very much depends on how neat you want the finished harness to look. If you're putting a lot of effort into making the swap look neat, then you're going to want to build the harness wire-by-wire in order to get the routing and lengths of all the wires "right". Just like everything else... if you don't care how neat it is, you can do it quickly and cheaply. True, my last harness I pulled each wire out of the PCM connector, routed it for a clean look and in the end it was 100% custom, but in that case its still pull from C11, reroute, put back into C11, (cut/crimp or just fold). Its not difficult, just time consuming. You still only have to "figure out" the 15-20 wires that join the two harness together. Rickady88GT JAN 24, 07:37 AM I relocated several plugs and rerouted the harness to clean it up. I also relocated the fuse relay box to the front spare tire area. I did not count the splices, but it was approximately A LOT. I am happy with the LS4. I love the sound most of all.