Hello all! First post here for me!
2008 Pontiac Torrent GXP (3.6) 115k miles.
Vehicle is now no longer running. Throwing multiple engine codes. The car was driving fine then it would run rough then fine then rough. VERY hit or miss.
Here are the codes from the Torrent....P0689P0300P0301P0302P0303P0304P0305P030 6P0562
I have since replaced the ECM with a brand new one. The dealership installed and flashed/programmed it and the issue remains. Very hit or miss when in operation will be fine one stop light the next the check engine light will flash and vehicle will run rough, a minute later....no issues no check engine light. No one can seem to figure the issue out. Anyone else experience this?

Breaking these out so we can read them:

P0300 - Random/Multiple Cylinder Misfire Detected
P0301 - misfire in cylinder 1
P0302 - misfire in cylinder 2
P0303 - misfire in cylinder 3
P0304 - misfire in cylinder 4
P0305 - misfire in cylinder 5
P0306 - misfire in cylinder 6
P0562 - System voltage low
P0689 - Problem with the engine control module (ECM) or powertrain control module (PCM) power relay feedback circuit

What is the voltage at the battery posts while it is running?

How many miles have you owned it?

Does it get maintained regularly?

Was this their attempt to fix the problem?
These require load testing of the circuits. Understand?

The voltage fluctuates from 14 to 11 to zero to 14 to 11 so on and so fourth. I have only owned it for a few hundred miles. Only had it a month. Engine looks VERY clean. Exhaust new. Interior immaculate. I will do synthetic oil changes every 4k from here on out. I am religious with maintenance on my vehicles.

Yes i do.

Load test the power and ground sides of the coil circuit.

Is this with a meter probing at the battery?

What happens with the same test but with all lights on and blower(*) running full blast?