So I installed LED taillights a while ago and that was when I learned about SRCK bulbs. Stupid things, so I ended up buying some different ones on ebay that actually turned out better and brighter. I tried the original regular wired led bulbs in the front turn signals and they would not work right. If in one way, the turn signal worked but not the parking lights, if installed reverse, the opposite. WTH! I removed the plug from the socket and used a multimeter to check the socket and it was a normal 3157 socket with the ground on either side. When I checked the pinout of the plug I noticed that the lt blue and black wires were flipped in the plug. It was the same for the drivers side. The harness was untouched and must have been done at the factory. I swapped the wires so that the lt blue wire was in pin 1 and the black ground wire was on pin 3. Now everything works. Is this how all the Trailblazers are wired? I wouldn't think so because I haven't heard of anyone talking about this.