One time, I tried an LED Bulb, it blew a fuse in the Fusebox near the front passenger seat. I'd forgotten that fusebox existed, had checked the ones in the engine compartment. I found out when the dealer told me! $50 lesson.
Another time, I don't recall exact circumstance, I had OEM taillights working but not the LOF Taillights. It was because of a small voltage drop, caused by a jumper wire not having perfect contact right on the blade of a fuse. Reinserted the jumper wire and fuse, and all was OK. Circuit was correct, but not complete.

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Majestic Blue 2006 XE CC 2WD Big Tow
AEM BruteForce CAI; PowerAid TBS; MagnaFlow 3" x 24" Muffler; UpRev 93 Tuned; Detroit TrueTrac
Stillen Front and Rear AntiSway Bars, Diff. Cover, Front Rotors & Pads
PRG 2-1/2" and 1" MiniLift, Street Traction Bars
DYNO: 308 RWHP & 380 RWTQ
~CRANK: 360 HP & 450 TQ
Born June 12, 2006
Adopted June 27, 2006
14.792 secs at 91.04 mph prior to TrueTrac
Member of the Charm City TitansIRC VK56 Member "Special Operations"