I must say thanks again for your help on the front R turn signal.
Your posts of the "2005 system wiring diagrams Chevrlet - Cobalt" among with the BCM connector C1 pin out was all of the data needed.
A few quick tests verified a signal was coming out of the BCM and out of the under hood fuse block.....yet no flash from a known good bulb. All other lights work and I had continuity from the blue wire just out side the fuse block, through to the lamp connector.....
It turned out to just needing a little tweaking on the bulb's socket connectors and now we have FLASH!
So thanks again Coby7
---------- Post added at 05:11 AM ---------- Previous post was at 04:47 AM ----------
Was posting update and poof ...lost all of the edits...
Was to comment on all of the pm up to date including....
Fuel pump & filter
Plugs coil pack & ICM
Both O2 sensors
TB cleaning with idle training
Heater/AC fan With new resistor, switch and the last connector before G203!!!
So now after about 1-1/2hr of 65-75mph on new Cat....
down to last 2 IM monitors, CAT and EVAP.
Hopefully the next drive cycle should set one or the other maybe both without triggering that pesky P0420.