I have an 03 lesabre 3.8l v6...
Engine runs rough, shifting is delayed, upper radiator hose collapses as engine cools, lights on dash and stereo are very dim during day to the point that I cant read them...
Multiple engine codes:
p0201 injector circuit cylinder 1
p0128 coolant temp below reg (probably bc I removed tstat)
u1040 loss of communication with ebcm
p1811 max adaptive long shifting
p0420 cat sys below thresh
p0300 multiple random misfires

Those are all different codes....methinks you have had problems, and have ignored them, and they have added up?

The injector code could be a bad injector...could also be the wiring to it, or a bad PCM.....

Yes, P0128 will come on if the thermostat is removed....why did you remove it?

U1040 could be caused by loss of ground or power to the EBCM, open/shorted serial data line, or bad EBCM...

P1811, is usually an internal transmission problem......usual fix is a pressure control solenoid, but there could be other problems too....What is the condition of the transmission fluid and level?

P0420 is usually an indication of a bad catalytic converter......is there a loss of power while accelerating?

P0300 is a misfire....the bad injector circuit could cause the engine to misfire....or you could have secondary ignition failure, like coils, plugs, wires, etc.....Driving the vehicle with a misfire, could cause catalytic converter damage.....

the lights dimming sounds like a power or ground issue. i would clean the battery and grounds cables under the seat and the one from the pass side frame to the engine by the starter. sometimes they are separate, sometimes power issues cause a bunch of crazy codes.

JW, those dimming lights to me sound like a light sensor problem.......if the auto light system thinks it dark, during daylight, the auto light come on, and it hard to see your radio/dash/hvac in the daylight.....

this would be confirmed by if they look ok at night, and their dimmer control works....