What does LED2 blinking mean?

I just replaced the EFI chip, micro-soldered it myself - yes - I know how to do it :) and everything looks good on the board except now my iMac won’t boot. LED1 turns on as soon as I plug it in and then LED2 turns on and off every 5 seconds. Can’t actually do a PRAM or SMC reset since it actually never boots. I’ve checked all the connections and I’m pretty sure I didn’t short anything on the board (pic attached).

Any ideas where I should start first?