[8500lbs]

it is a dual filament bulb. that is why one circut works and other does not. To change them first lift the tail gate and you will see two torque screws on the insde door jam of each light housing. remove these screws and then you can see the door side of the light housing can gently be pulled forward about an inch or so. after you gently pull forward, you want to try and slide the light housing towards the inside (aka, towards the door or lift gate.) after you slide towards the inside you will feel the entire light housing come loose. Just pull forward and twist the bulb socket and pull out. replace bulb and reverse process. all the bulbs in the rear are 3157 bulbs. Hope this helps. If you need any more help or need some photos or something just let me know.

Thanks
B