I have a 2000 buick lesabre limited with the standard 3.8 series II engine.
just the other day it started running very rough at idle loss of power and a constant miss.
i have replaced the air filter the plug wires the spark plugs and 2 of the coils
i still get code p0300. i have steady vacume .fuel pump is only 4 month old
no fuel leaking from regulator my injectors all have the same resistance within a ohm
or 2 .When the car is running i pulled each injector connector off one at a time
cyl 1 and 4 made no change to the engine. so i then checked for spark on all cyl. againe
no spark at 1 and 4 the other four cyl have spark. i then pulled the coil for 1 and 4 off it is a new coil at the icm i get 12 volts at this coils location but no switching signal.So the is running on 4 of 6 cyl .Any body have any ideas could this be the ICM.

I would pull the coil for 1 and 4 and one of the others that you know is working and check the voltage at each prong on the ICM and if your low on the spot for 1 and 4 replace the icm

I have 12 volts at coil 1and 4 location on the ICM but no switching signal at that location.

usually when the icm fails none of the cyl. have spark, but i cant think of anything else it may be. if four are working i would think everything to that point is fine.

Sounds like the ICM may be bad. Generally it will effect all coils, but not always.

Thanks for everybodys input the problem was the icm it would run on cyl 2 3 5 and 6
no spark on cyl 1 and 4 .I pulled one off a 2001 impala at a local junk yard the car ran better immediately the flashing check engine light stoped then after about a hour drive the solid check engine light that was on forever whent out on its own .That icm must have been failing
for quite some time

Thanks again Dan

Good to hear. I'll mark this as fixed.