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Discussion Starter #1
So I've looked through a bunch of threads trying to figure this out myself, but I can't seem to find anything. I've got a 2005 Outback, auto trans. The reverse lights aren't working, I tried the usual suspects, lights, fuses, all good there. I saw a common issue was wiring splitting in or near the rubber boot on the tailgate, but all mine are just fine.

I tested the light plug with my multi-meter, and neither is getting any power when the car is in reverse. This is making me think it's probably the reverse sensor. I've been looking for the part, and all I can see is an option for the standard transmission. Does anyone know if the part is the same, or if I need to find something else?

Thanks for looking
 

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I saw a common issue was wiring splitting in or near the rubber boot on the tailgate, but all mine are just fine.
There's still a chance it is a broken wire in the right side rubber boot between the car body and the hatch. It wouldn't be the first time the wires at each end were checked visually, but subsequently the wire was found to be broken further up in the boot where it wasn't visible. Sometimes, pulling on each wire at both ends of the boot at the same time will result in one, or more, pulling out.

The wire that goes to the back-up lights is probably brown with a yellow stripe.
 

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2001 VDC Wagon - White pearl - 302,000 km
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It would seem that the inhibitor switch (sometimes called neutral safety switch) is wired in parallel to the MT reverse switch, suggesting the wiring diagram is serving both transmission types together. Does your dash display the appropriate gear selection when in reverse? Have you tried jiggling the shifter back and forth across the reverse detent?
 

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It would seem that the inhibitor switch (sometimes called neutral safety switch) is wired in parallel to the MT reverse switch, suggesting the wiring diagram is serving both transmission types together.
The wiring diagram is serving both transmission possibilities, but in reality, the wiring harness that's in the car will be for one or the other; in other words, if the car has an AT, then there is no parallel branch going off to connector B24 for the MT Back-up light switch. In the OP case, it's an automatic, so only the wiring to the inhibitor switch is involved.

The 2005 diagram (3rd Gen Outbacks) is somewhat different (see attached).

Based on the numerous posts here, failures of one or more electrical functions in the rear hatch of 3rd Gen Outbacks (2005-2009)are often due to broken wires at the flexible boot. This doesn't eliminate the inhibitor switch as a possibility, but at the least, a broken wire (or more than one) should be fully investigated.

http://www.subaruoutback.org/forums/80-electrical-electronics/116713-reverse-lites-08-obw.html
http://www.subaruoutback.org/forums/66-problems-maintenance/34967-reverse-lights-not-working-quick-fix.html
http://www.subaruoutback.org/forums/66-problems-maintenance/41443-replace-05-outback-hatch-wiring-harness.html#post3500441 (see also the links to other threads in this thread)

Also, in the 3rd Gen Outbacks, the fuse for the Backup lights (#18, 10 Amps, in cabin fuse panel) also powers the Daytime Running Light control module. There have been cases where the wire to backup lights had broken, and the open end shorted to a ground. This blows the fuse, which cuts the power to the DRL module. Without power to the DRL module, the headlights don't work. (See post #32 in http://www.subaruoutback.org/forums/80-electrical-electronics/35328-headlights-not-working.html)

One way to verify the wiring to the backup lights is to measure the resistance between connector D35, pin 10, and ground with the ignition Off. (See attached diagram.) The resistance should be quite low (close to zero Ohms) if the wiring to the backup light bulbs (bulbs installed in their sockets) and from there to ground, is intact. If the wire in the flexible boot is broken, the resistance will be high, i.e., >100 Ohms.

The challenge, however, is to access connector D35, which is behind the right side trim panel of the cargo area. Instead, if the boot ends are removed from the sheet metal openings and the brown with yellow stripe wire is located at both ends (as far away from the boot as possible) a small pin can be inserted through the insulation to contact the wire strands inside. If there's a break, there will be high resistance from the pin to ground when measured at the measured at the car body side, but low resistance when measured at the hatch side of the boot. In this regard, it's important to use a very small diameter pin, and to only push it in enough to make contact, but not go through, the wire, so as to not add a point of weakness in the insulation or the wire inside.
 

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Discussion Starter #5
I didn't think to check both sides of the boot. I checked the tailgate side initially, and it looked all good, even stayed put when I pulled it. I checked the body side this morning, and there was the separation. There were also a few other wires that had their insulation cut. After spending the better part of my morning re-wiring and wrapping it up, the reverse lights are working again.

Thanks for the help guys.
 

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The wiring diagram is serving both transmission possibilities, but in reality, the wiring harness that's in the car will be for one or the other; in other words, if the car has an AT, then there is no parallel branch going off to connector B24 for the MT Back-up light switch. In the OP case, it's an automatic, so only the wiring to the inhibitor switch is involved.
Yes, I was implying that Subaru had not created a separate diagram for each transmission type.
 
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