Last Updated
15 September, 2004

Rewiring Fog Lights on a '93 MR2

One of the mysteries of the '93 MR2 is why the fog lights only work with the headlights turned on. If you've ever driven in heavy fog, you know that the headlights only make things worse, and the fog lights are placed down low to minimize the nasty reflections that make driving in fog so difficult.

Jeff Bihn, Marcus Hall, and Jeffrey Ho See have contributed suggestions to the MR2.COM archives that describe modifications to remedy this condition. Unfortunately, these are mostly text descriptions. I'm not very skilled when it comes to electrical mods, so photos are always appreciated in addition to text descriptions and/or schematics. Hopefully the photos I've included in this guide will help others who wish to make this modification.

Update (07-16-2001)
Jesse Grice reports that this procedure also works on the 1992 MR2 (Thanks, Jesse).

If you wish to see the articles mentioned previously, they can be found here:

'91-'92 Fog Light Modification  
'94 Fog Light Modification

Finally, remember that this is only a guide -- not gospel. What you do to YOUR vehicle is YOUR responsibility. I do not endorse, approve, authorize, or otherwise encourage you to make alterations to your vehicle. Be careful, and recognize the dangers associated with modifications to your vehicle's critical systems, like electrical, engine, brakes, etc.

Please contact me if you have comments or suggestions about the article or the project, or if you find errors on these pages. 

Tools Needed

  • Needle-nose pliers

  • Small, flat blade screwdriver

  • 10mm, 12mm sockets and/or wrenches

  • Wire cutters, strippers

  • Soldering iron, solder, electrical tape

Doing It

My goal was to modify the wiring to enable the fog lights to run completely independently of the other lights. My only concern is that they run unswitched, e.g., they run with the key in the off position. It's more useful that way, but I hope I don't accidentally leave them on some day and kill my battery. There is an indicator light in the gauge cluster, but I'm not sure if that is enough for me. My memory seems worse every day.

UPDATE: Ricky Benitez supplied a mod that provides power only when the ignition is on, eliminating worries about leaving the lights on and subsequently discharging the battery. More about this further along in this guide.

Another decision is whether to disconnect the battery while working on this modification. I didn't, but it's probably prudent to do so, as you will be splicing wires under the fuse panel.

First off, you'll have to decide how much stuff to remove from your front trunk. I removed the spare tire and the entire inner lining to make working simpler, but I guess you could get by without entirely removing it.

On the right-hand side of the trunk is the fuse panel:
FogLight-001.jpg (157999 bytes)
Notice in the lower right corner that the relay location for the fog light is indicated by "FR FOG". Remove the cover of the fuse panel.

The red ovals indicate two areas (there are others not in the photo) where you'll need to remove fasteners holding the retaining brackets for the fuse panel. In my case, I also needed to remove the reinforcing brace, a multi-armed brace that attaches in several places near the center of the trunk. I'm not sure this is entirely necessary, but it made it easier to work on the back of the fuse panel, and it enable me to clean out some rustproofing "goop" that was sprayed everywhere. 

Once the top cover is removed, you can see the fog light relay in the upper right corner. If you enlarge this photo, you'll notice that the printed schematic on the case of the relay lists four terminals: 1, 2, 3, and 5. This was a bit of a problem, since both the BGB and Marcus Hall referred to terminals 1, 2, 3, and 4. Not a biggie, but disconcerting for a novice electrician. 
FogLight-002.jpg (132980 bytes)
I chose to remove the fog light relay, since I was planning on soldering some leads attached directly to the relay terminals.

Turn the fuse panel over, and remove the back cover. This is made more complicated by the four clips that are used to retain the cover. To free them, you need to work a small screwdriver in from the top and unlatch the locking mechanism for each clip. 

Once the cover is removed, you'll have lots of multi-colored wires within your view:
FogLight-003a.jpg (113909 bytes)
The photo focuses on the four wires leading to the fog light relay. I've numbered them according to the terminal numbers on the relay. The two wires we are interested in are #2 and #5. 

Wire #2 (red w/yellow stripe) only receives power when the low-beam headlights are powered on, so we need to remove that dependency. Luckily, #5 is hot at all times. All we need to do is cut Wire #2 and splice it to Wire #5, as shown below:
FogLight-007a.jpg (140783 bytes)
The larger red circle shows the finished soldered joint. The smaller red circle shows where I've taped off the other end of Wire #2.

NOTE: Splicing Wire #2 into the black w/orange stripe wire (which goes to the FAN MAIN relay) instead of Wire #5 above will provide power only when the ignition is in the ON position, an excellent suggestion for preventing accidental battery discharge. Thanks go to Ricky Benitez at for this and numerous other MR2 tips.

After carefully taping the splice to prevent any shorts, you can replace the back cover, and re-mount the fuse panel in its original location. Replace the relay and you're ready to try it out......NOT!

Ah, yes, another Toyota mystery. All you seem to have accomplished is that the fog lights will now come on even if the high beams are on. Not exactly what I was looking for. I pored over the BGB's wiring diagram, but I got lost until I re-read Marcus Hall's guide that mentions that "some" MR2's run the ground wire over to the retract relay. This must be the year. Why this is so complicated is a subject for discussion, but another time. I'll avoid speculating and get on with the fix.

Move your attention to the left side of the front trunk, and you'll see a HUGE, bright green electrical component with a mass of wires going into the bottom:
FogLight-008.jpg (120036 bytes)
This is the retract relay, and your job is simple. Slide the relay off its mounting bracket, remove the connector from the bottom, and locate the only wire in the bundle that's red with a black stripe. It's the second wire in from one of the connector edges.
You simply need to cut this wire and ground it. You can choose another splicing operation as we did with the fuse panel, but I chose to ground it to a frame bolt. It required slitting the wire covering open, cutting the wire, splicing a length (about 6") of wire fitted with a ring connector, then taping the wire bundle back up. Here's the finished product:
FogLight-010.jpg (171385 bytes)
I fastened the ring connector to the same bolt that two other wires were grounded to, right near the wire bundle:
FogLight-011.jpg (90128 bytes)
This solved the mystery, and now the fog lights are totally independent of the other lighting systems. 
Dave Martin
1993 MR2 Turbo