Attached is a description for adding fear foglights to E34s that don't have the wires per installed from the factory. This method bypasses the LKM in the electronic box under the hood, but gives you the rear foglamp indicator on the dash.

Procedure

This method gives you fuse protected rear foglights with the factory dash indicator without going thru the light control module in the electronics box under the hood.

• Euro fog light switch p# 61 318-351-238 BMA or Pacific BMW
• 2 bulb sockets (same as backup bulb socket, dealer)
• 1 generic fog light relay with wiring harness (usually 30amp 12v. it's overkill, but they are cheap and available)
• 15' 24 gauge Teflon insulated wire.
• 15' 18 gauge wire
• 1 1.2w dash indicator lamp with socket (Wagner makes one for BMW comes 2 for $2.99).
• 2 inline fuses (1-2amp and 1 5 amp)

You must solder the switched + for the foglight switch to the rear foglamp indicator bulb contact on the bulb itself. Use a meter to see which side of the circuit board on back of instrument panel is grounded, wire goes to opposite side on bulb (if it's wrong 2a fuse will blow)
Rear foglight socket must be cut out and cleaned up with xacto knife and or small file so that backup light socket will fit in. Follow the pattern you see on the plastic plug. The contacts for the bulbs can be made from old speednuts or other material that you can solder wires to, look at the other conectors for pattern.

ALTERNATE PROCEDURE FROM attackeagle

Step 1: Installing Euro Fog Switch…
The switch will simply plug into the existing harness and connector,
however it will be missing the 4th wire for the rear fog output.
Instead of cutting the complete plug out to solder in a entire Euro harness plug, I found it easier to disassemble the existing connector and add the one missing wire to the original connector.

Step 2: INDICATOR BULB
The prior instructions on e34.net about how to add the indicator bulb
annoyed the hell out of me. The instructions and diagram previously indicated to solder
the wire from the switch directly to the bulb’s positive side.

Not good idea IMO.

Since I had the steering column out and the battery disconnected, I decided to pull the cluster and find which pin was the one for the rear fog indicator light with my multimeter. It is in the long connector on the left side.

After removing the slide off white outer shell, I shot a picture so you can see where the connector is missing the "female side" for the rear fog indicator bulb +. The pin is on the cluster itself, just not in the connector or harness. All you need is wire and the socket side of the pin installed in the connector to 'do it right' so the bulb can be changed out.
The location to add it is 2nd from the bottom right hand side (above a grey/red, and catty cornered from a yellow). see picture below:

I added a tiny pin socket to the connector, and wired that to the fog light switch's rear pin
The tiny pin socket i got from a spare connector, like those used for the 3 pin mirror, or the later 4 pin connector c-pillar light, but it still needed to be shaved down with a dremel to fit into the dash connector.
Now I do have my amber rear fog indicator light, just as it should be.

Step 3: wiring to the relay.

some people have asked questions about the wiring, how I ran it and if I had any pics.
I have no pics, as there is nothing to take a picture of.
I ran the wire from the fog switch down the left side of the car to the rear seat area, where it crosses with other wiring to the
battery.
It is easy to tie the wire to existing wiring above the pedal box this way. The fog switch area opens into the stereo “hollow” and
straight down. It would be inconvenient to try and run the wire across and above the glovebox IMO. In addition, I had already
installed wiring in that area for the Hella E-code tilt motors in this area and knew exactly how I wanted to run it.

Step 4: Relay

Very simple: Follow diagram above.
87: 12+ From Battery
30: To Rear Fogs
86: From Switch
85: Ground
87a: Not used

I picked up a relay that had a diode already in it to protect the OEM switch from induced voltage (arcing) when turned off.
This I tucked just to the right of the battery, where it is easy to get to if needed, but out of the way. The diagram was very helpful to me, and I hope everyone can read it.

Step 5: Relay to Tailgate

I ran a single wire into the tailgate along the right side. I chose that side because the wire bundle is smaller on the right side,
and the battery is on that side as well.
Tuck the wire under the backseat area and under the side panels until you reach the right side cover near the gate. Open the
hatch, remove the right harness grommet and with a wire hanger or a wire puller tool reach down inside the c pillar so you can
bring the wire up and thru the larger grommet. Then either try to run it inside the mesh or just run it alongside the existing meshed harness. Run it thru the existing harness holders and guides after removing the side covers.

But here is a pictures I shot where you can see how I ran the wire into the hinge area. It comes up thru the same grommet that holds the rest of the bundle, and follows all the rest the wiring thru the hinge and into the gate.

you can barely see the green ( fog ) wire in this picture because I moved the 3rd brakelight wires aside for the picture... It is the
only place it is visible in the entire run as it goes into the factory gate channel and follows the existing wiring into the gate itself

Step 6: Removing the Lights from the tailgate to fit contacts and wiring them up

It's easy to take out the reverse/foglight assemblies if you have a 1/4 drive 8mm deep well socket. If not you have to take the
entire inner gate skin off. Tourings use a bulb socket that is not the same as the Sedan... it is the same as an E32/ or E34 Touring reverse socket.
I found it much easier to take the single wire on the right side and then parallel the positive leads by running a jumper wire
from the right side contact to the left.

you can see how these contacts I scavenged from a set of junk sedan taillights would not work in the touring's very differently shaped sockets. I straightened them flat and then rebent them to the desired shape with a crescent as a mini vice/anvil and a body hammer.

Then I used a straight pick tool and the tiny body hammer to "stake" them once they were in, so they would spread to become
pressure fit like oem ones. It' s hard to see the reverse contacts (it's noon and the gate is skywards to shoot this) but the oem ones are shaped like the letters "IL" with the top of the "IL" being joined and that top portion is inserted into a slot.
The sedan taillights use a horizontal "U" shaped one that clips with the open end over the edge of the bucket itself.
SO I had to straighten them and reshape them completely. They look oem and that is what I wanted so it was worth the effort.

I used the existing ground (brown) for the reverse bulbs as the ground for the fog light bulbs.
It was a simple matter to tin the wires and solder them together before the black 4 pin connector (connector pictured above). Since the negative side is soldered to the existing negative on the light, it uses the same connector. The positive wire has a double heat shrunk spade and socket so it can also be disconnected if there is a reason to remove the assembly later.

I was impressed by the light pattern from the rear fogs.
It isn't just an extra positioning light, but actually illuminates far behind you like the brake lights do.

I hope this helps you install rear fogs in your e34 touring... sedans are apparently even easier.