Hey guys,

Would someone please explain how our wiring harnesses work.

For instance, I know with some cars there is a cabin harness that controls all of the lighting, radio, etc. and then there is a separate "stand alone" engine harness. These two harnesses are only connected by a connection on the firewall that provides the engine harness with ign+ and provides constant power to both.

So my question, (i've looked at the f.s.m.'s wiring diagrams) but I don't understand how ours works. Are they fully integrated? Are there separate harnesses? Are there plugs that detach?

My question specifically pertains to non-DBW cars, but any additional information on the DBW would be helpful to the community, too.

Thanks!

 

Engine harness connects to the ECU using two plug. The ECU plug into a dash harness the feeds the dash cluster and other car mounted system. The Dash feeds several car systems, EPS to name one. This dash harness is connection to another dash harness and connects to the right and left rear branches, inside the car. It also connects to the front harness.

So depending on the system you are looking into, it could be in 4 harnesses.

What are you trying to do? Swap a NON-DBW engine into a DBW Car or the reverse?

 

Thanks for your reply stratocaster!

So the engine harness's two plugs are those serving two functions: sending data to the engine (timing, coil pack firing, etc.) and receiving data back from the engine (VSS, O2, temperature, etc.)

The dash harness, the right and left rear branches, and the front harness - are the all non-engine related systems i.e. turn signals, lights, etc.?

 

Well I went out and looked in the bay today and this is what I found.

There's 6 grommet/holes in the firewall that I can see that let wires through. 2 on the passenger/battery side. 4 on the driver's side.

Passenger Side:
1. Has 2 wires, one goes to the battery and 1 to the EPS box
2. Has several wires and it looks like it goes to corner lights. But it also looks like it connects to the a/c dryer?

Driver Side
1. Has 2 wires goes to a small fuse box. The other 2 exit/entrances to that fuse box lead to a really big bundle of wires
2. Huge group of wires that seem to go all over the driver side of the engine bay and to the driver side headlights
3. Connect to another grouping of wires
4. Connect to another grouping of wires

I can take pics if that helps. But really what would be awesome, is if there is a diagram that shows where each group of these wires goes to. I presume that's what the service manuals wiring diagram is supposed to show, but I don't understand how to find Passenger Side #1 or Driverside #3, etc.

Thanks!

 

Looking at the manual and it is starting to make sense. For those of you that are confused too, check out Chapter 22 of the f.s.m.
The systems seem to all connect together, so you have to follow the "trail"...