My 2007 Yukon message center says "service 4wd",,,The light on the indacator just blinks,,,I can hear the transfer case engage and when it does it locks the drive shaft in like it's supposed to,,But the front axle doesn't lock in,,I bought another actuator for the axle and plugged it in a selected "4wd" but the actuator didn't move,nor did the old one,,I'm thinking it needs a software update or perhaps a bad wiring harness,,,Any thoughts?
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