So long story short my windshield leaked on my 2000 psd 2x4 xlt Crew cab long bed auto truck. The underdash harness and fuse power distribution box corroded and malfunctioned. My dad gave me the truck. I pulled the dash and purchased a used harness and box on ebay. Everything looks good and matches up except one plug. It comes out of the green loom at the fire wall. On my stock harness it had a plug but on the replacement harness there is no provision for it. Can anyone tell me what this plug is and what it's function is? It's mid way under the dash almost center.