Hey scotty, i have a 2004 chevy monte carlo 3.8L not supercharged. i have been through hell with this thing. driving home one day it started to misfire so i pulled code to see which one it was misfiring on, it was 3 and 6. i looked up the diagram on the firing order and 3 and 6 were on the same coil pack. so to rule it out as a problem i swapped 2 coil packs and it was still misfiring on 3 and 6. i then checked to make sure it was even getting spark and it wasn’t. i swapped wires with ones that were sparking and made sure they were in the correct firing order (i even triple checked) and still no spark. after looking around i’ve noticed there’s a security light flashing and that it can cause a whole lot of problems, one of which the car not starting at all but mine starts. i have checked every wire that goes to them to make sure they’re seated correctly and not corroded. is there any fixes you would know about that i can’t think of?
try swapping spark plugs around.
Otherwise you may have a failed ICM
You swapped coils and the NO SPARK didn't follow the coil.
It's likely the ICM (Ignition Control Module) like @mmj said because your car doesn't use the PCM to control the ignition coils during starting. Under 400 rpms it's controlled by the ICM.
You'll see 2 terminals on the ICM that plugs into the coil.
You can test them with an LED test light. Key on, one terminal should have battery voltage.
The other terminal should produce a Ground switching signal as you crank the engine
I'll bet the spark plugs are 18 years old and look like burnt toast.
If the security light is on, try another key and see if it makes any difference.
The PASSLOCK anti-theft system in GM vehicles has nothing to do with the ignition system, and would not cause misfire. It disables the fuel so engine would not even start.