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This page has been added since the initial write-up was made available. I had gotten a letter from MikeJ who was gathering parts for an AW4 swap. He had read ScottK's write-up and wrote me to ask how the backup lights were wired. ScottK's write-up didn't address it and up until this page was added, my write-up didn't either.
So here is the necessary info to get your lights hooked up.
The XJ, when equipped with an AW4 tranny, powers the backup lights via the +12V that comes from the Transmission Range Sensor (pin 6). (That is the assembly that the 8 pin Gray plug attaches to on the passenger side of the AW4). The same +12V can be obtained at the TCU (pin 18).
If I had given some thought to the backup lights when I still had the AW4 sitting on the floor, I would have soldered about 3 feet of wire to the wire on pin 6 of the Transmission Range Sensor and left it until I got the tranny installed. But I didn't, so here is what I did post installation.
Looking down at the top of AW4, you will see the wire harness that was plugged into the AX-15. This was connected to the backup light switch on the AX-15. ScottK mentioned in his write-up that you should remove this plug and toss it. I found it easier to modify the plug and continue using it.
Slide the red clip to one side so that you can pull the plug apart and temporarily separate it from the TJ's harness. If you have room to work on it, you can leave the plug in place if you wish. Remove the tape that the factory folks wrapped around the wires. When you do, you will see that pins 1 and 3 of the 4 conductor plug are connected together. This is the "jumper" wire that, when not removed, bypasses the Park/Neutral Safety Switch on the AW4. If you want to be able to only start your TJ in Park or Neutral, cut both ends of the jumper next to the body of the plug.
I then cut the two conductor AX-15 backup light connector off of the harness, leaving the two wires (coming out of the 4 pin connector) as long as possible. One of these two wires is +12V (Violet/White) and won't be used. I folded it in half and then slipped a piece of heat shrink tubing over it and sealed it up.
The remaining needs to be connected to the Reverse circuit. I soldered a length of 18 gauge wire to it and connected it to the above mentioned pin 18 at the TCU. When the shifter is placed into Reverse, the transmission range sensor will output +12V to that wire and the backup lights will illuminate.
I slipped the wire I soldered onto the Violet/Black wire into some loom material and routed it along the driver's side of the tranny and then up through the hole in the firewall where I connected it to the TCU.
As I said earlier, had I given this some consideration before
the tranny was installed, I would have been dealing with a foot or two of wire
connected between the shifter on the side of the tranny and this modified plug.
More AW-4 Tranny Swap