(WIRING) GSL-SE ECU Harness Wiring Diagnosis
 

I'm most of the way through re-wrapping my harness, and I've come across a problem. At the end of the harness, there's a Green, Orange, and two White connectors that attach to solenoids and valves on the rat's nest. They're all pulled together in what looks like a common ground that's black with a white stripe, and occasional red or brown spots on it. This wire is cut, and I can't see from the wiring diagram where it should go.

I have two independent ground lugs that are intact, and routed with the other 4 plugs. I've looked through the wiring diagram on page 50-16, and I don't see a common wire for these, or where it goes. Can someone help me out?

Hey Crit,
Those 2 independent ground lugs bolt to the top of the rear rotor housing using the same bolt that holds the rats nest to the engine.

Yeah, I was just stating that so folks don't think I have this open black wire confused with one of those two lugs. The lugs are intact, and there's a third black wire without a home. On page 50-16 of the FSM, the wire runs over the top of the diagram, and is used to feed several sensors, which are then grounded by the ECU. The black wire that I have appears to come from plug B-29, which is the Circuit Opening Relay - a 6-pin connector in which every pin is used. When I look at my harness (and yours), there isn't a single 6-pin plug on it with more than 4 pins used. I'm totally confused, and don't want to cut open the template harness to see where it goes. I imagine it was pulled from a splice somewhere, but I don't see where it could be.

The majority of solenoids and electrical components on most engines will share a common POWER source wire,not a ground.

The colored,smaller wire from each component is actually the ground wire that leads to the ECU.The ECU controls each item by opening or closing the ground circuit,this way the ECU doesnt have to channel very much current.When the ignition key is turned on,the circuit opening relay and/or main engine relay are responsible for sending the 10-20 amps of power needed to control the various solenoids,injectors and switches on the engine,through the large black/white wire.But since the ECU controls the ground side of each item,there is not actually any action from any of these items until the ECU says so.This is the same way that the FC engines,and most automobile engine electrical systems are setup.

You're right, but I originally called it a ground because it was black. I know, though, that the ECU grounds them indpendently. So, where did this wire come from? I see one splice that's a soldered crimp connection for the ACV, but it's still very tight, so I don't think it wiggled out of there. I'm curious if anyone can tell me where that wire is supposed to go in the harness. I just realized that it might dogleg out to a connector, where it's spliced at the pin. I'll keep looking, but I'm curious if anyone would know. Anyone have an open harness handy?

Yahaa, found it. It coyly fatigued itself on the backside of that splice for the ACV. Off to the soldering iron !!!

Very informative post Steve, thank you. I did not know most of what you posted and did think the black/white wire was a common ground, not a power supply. This may help me find my power drain that suddenly showed up in the widebody.

This is true. BTW the black with a white stripe and the black with a yellow stripe found in the S3 S4 S5 wiring diagrams I've looked over are 99 percent of the time power wires for the fuel injection and emissions stuff. I know because I wired my car for an S4 then undid it and put teh S5 wiring in when I got that motor instead.

That is correct.

On 2nd gens,the injectors/coils and all other solenoids are directly powered up by the main relay through the black/yellow and black/white wires respectively.The power for those two circuits comes directly from the two EGI fuses in the underhood fuse block of the FC.From the main relay the power goes under the dash and through the dashboard-to-engine harness connector, upstream of the yellow ECU gangplugs.This is a common hangup point for FC swap guys, since many people assume that all wires from the engine lead to the ECU......which is mostly true of the colored ground wires,but not the high current feed wires.
For the GSL-SE power comes from the 4th, extra fusible link that particular car has, v/s the 12A cars.I dont believe the SE has two seperate EFI power circuits since the ignition is not ECU controlled and there are less solenoids on the engine compared to the the FC engines.But it sounds like they are laid out very similarly,with similar color codings.