tbirdsc35th provided the where, now I'll provide the what.
Unhook the actuator on the passenger side front. There is a plastic cover which you remove, then push the 2 tabs inwards and lift up on the whole assembly. Leave it plugged in, then go try the auto/firm switch and see if the flashing goes away.
If so (it will) then squirt a couple of drops of oil in that shock tower, and with a set of needle nose pliers, turn the flat shaft back and forth a few times, reconnect the actuator and try again.
If the flashing comes back, the shock needs to be replaced. You have the option to also simply leave the actuator unhooked as long as the shock is not worn out.