Do a search on here about Park lamp problems.
I and several others on here, have had this issue and found it to be the Power Distribution Centre.....the fuse box to you and I lol.
There are internal printed circuits in it and they corrode over time, with the elements etc.
These either produce an open circuit, or high resistance circuit.
This causes the front control module, to not activate the park lamp relay and swich on the rear lights.
Jumpering the park lamp relay as you have, proves that it's the fuse box.
Here's what the manual says :-
"Coil Ground Terminal of the park lamp relay - The coil ground terminal
(85) is connected to a control output of the Front
Control Module (FCM) through a park lamp relay
control circuit. The FCM controls park lamp operation
by controlling a ground path through this circuit."
That's what I did to prove it was the fuse box by jumpering pins 30 to pin 87 on the park lamp relay. The lights should all now switch on and prove that everything going towards the park and running lights, is OK. Fuses wiring etc. Many people have done in the past including as I say myself to test this out.
The fuse box is an expensive replacement and I think off the top of my head, cost the last person I read about who replaced it him self which is very easy to do, about $450.
There was a write up somewhere of a guy who resoldered the earth retun paths in the fuse box and did a cheap but somewhat involved fix.
I temporarily jumpered the park lamp relay so I could use my truck, but I had to disconect the jumper everytime I left the truck, otherwise it would run the battery down.
Someone on here might chime in?
Hope this points you in the right direction.
Last edited by abarmby; 11-26-2010 at 08:46 AM.