2003 chevy trailblazer_ls
Just got a used pcm off from eBay. The vendor "flashed" my vin number into the pcm, supposively as calibrated software claiming "ready to install." I bought this to use as my "spare stock unit." I'm preparing to send my current pcm on the truck to PCMForLess tuning. So I thought it was time to install the spare one before I mail it in because I need a running vehicle. Well, I put the spare one in and plugged it all together. I turn the key and nothing. The SECURITY light flashes at me when I attempt to crank it. Someone told me it needs the security relearn procedure. But how? Anyone with exact instructions? Thank you.