Hello, I'm a new member who's finishing up a S4 turbo & 5sp swap into a S4 NA/auto chassis. The time has come to start the car and I've realized I'm not getting power to the coil packs. I noticed a harbinger to this problem when I was wiring in an electric fan and tried to use the switched 12v signal at the check connector near the drivers' front strut tower. That check connector (6 pin) only has 2.3ish volts at key on to the B/W wire, which is the power wire for the EGI COMP circuit I believe. Similarly, the variable resistor only has 2.3v as well instead of 12, and things like the TPS and pressure sensor which I understand should see 5v only have a little over 1v. So it's like everything on that circuit has around 1/5 of the voltage it should, and the coils which I guess are on the EGI INJ circuit (B/Y wire) get no voltage to speak of.

Both the EGI COMP and EGI INJ fuses are good, as is the Engine fuse near the driver's foot.

Would the ECU be withholding voltage for any reason? I don't have any of the 4 solenoid valves plugged in, since I'm using a S5 turbo and don't have any smog equipment in the car. Does the ECU want to see those before it sends proper voltage? There are a few other wires left unused, like the ASV and subzero system and such. Are there any of those connections that should be jumpered together before I'll get proper voltage to the rest?

I've also had to bypass the inhibitor switch since the car used to be auto, I've jumped the B/W and B/R wires in that plug which allows the car to start. I don't think that should have any effect on it, but figured I'd provide that information.

The CAS checks out using the ohm test, I don't think that's the problem with the coils.
My wiring harness is in good shape and I doubt it's shorting out anywhere, but that's always possible I suppose.

I've been poking through the FSM wiring diagrams but haven't found any clues yet. If anyone has an idea of something to check that would be appreciated. Thanks.

 

Sounds like the main relay is the issue as it takes the voltage from both EGI fuses and relays the voltage to the coils, injectors, ECU and so on. Try jumpering two sets of wires at the relay (has two plugs and focus on the plug w/4 wires). If you jumper the Black/Green wire to the Black/Yellow wire that will power the coils and injectors. If you jumper the White/Blue wire to the B/W wire it will power the ECU (and B/W wire in the Green check connector which you spoke of). So there!

 

You da man satch! I began to suspect the main relay last night after more looking at the FSM, now I know what to do about it. I'll try that tonight and let you know.

 

Well, the problem was surrounding the main relay. I started by jumping the wires and getting good voltage everywhere it should be. Checked the relay was getting ignition voltage, which it was, then bench tested the relay. It worked on the bench so I rechecked the signal wire - it worked when I used a separate chassis ground but not when I put both multimeter leads on the 2 prongs of the relay signal plug.

So I searched around for where that relay grounds and found an answer of yours in another thread, took out the trailing coil and there was the ground plug, just hanging out inches away from where it should go. Not sure why I unplugged it in the first place, but nice easy fix, thanks satch

 

Yours was a rather easy fix based on the symptoms the car was exhibiting.