I've got an '02 OBW, and I recently discovered that the high mounted (third) brake light isn't turning on. All of the other lights work fine. I checked the harness and it looks in good shape - there is no sign of damage where it goes into the hatch (common on the gen 3's).

 

I was able to determine that it's some kinda ground problem. My temporary fix was to hook up a wire to one of the bulb housings and ground it locally.

 

I took some DMM readings:
D39 is the HM stop connector, D49 is LH finisher, D42 is RH finisher.

D49+D42 pin1 to D39 pin1 look good - zero ohms
D49+D42 pin2 to D39 pin2 = inf.

Does anyone know where the D39 ground joins the other grounds? It joins
the harness at the top of the inside hatch. Best I can figure, it must
go down to the D33 plug. Do all the grounds get crimped together in a
plug, or are they spliced in along the way?

I did get some non-zero readings from the finisher grounds, but I'm
going to chalk that up to background resistance. And this doesn't make
sense, but I'll mention it - D49(1) to D42(2) gave me a non-zero as well
- both plugs were unplugged from the bulbs...

 

Thanks for any help!

 

You'll need to remove the plastic from the rear of the actual hatch (both sides) as well as the bottom panel. With the bare metal exposed, you'll see there are probably 2-4 different grounding points. The top panel that conceals the headliner where it meets the top of the hatch might also have another ground there that's typically tied into the dome light. I snagged a 98' rear hatch and it should be fairly similar as yours.

 

If the bulbs are working with your makeshift ground, then I'd trace the wire by sight and replace the crimping where it goes to body. I've seen several crimpings on mine that appear to be hand-crimped. Whether that's factory or something after it was sold, I dunno. But they look like they can be suspect as the quality isn't exactly high-end.

 

If your lights aren't working with new ground, LED can and will quit working over time. If you have bulbs hiding behind a faux LED reflector panel, those burn out too but most don't realize until there's zero light coming from them and think it's electrical when it's just a couple dead bulbs. I've even seen both rear running lights go around the same time, which I thought was electrical, but upon inspection of the filament, both were kaput.