Lost communication with ECM?

Does this car have water damage? I would try a hard system reboot to see if things change. This guide can help, but first check all fuse with the systems on, this guide can help:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

U0300 - Internal Control Module Software Incompatibility
U0155 - Lost Communication with Instrument Panel Cluster (IPC) Control Module
U0140 - Lost Communication with Body Control Module (BCM)

https://www.2carpros.com/articles/step-by-step-guide-performing-a-hard-system-reboot-for-your-vehicles-electronics-systems

There are three fuse panels, one under the hood, one behind the glove box and the last one in the rear of the car. Do this first and get back to me. Check out the images (below).

No water damage, but now after the bleeding no hot air from vents. I tried it once after I did the update one of the hoses, and I got heat. But after a while I started it again and nothing, so I think there may still be air. When I got air the temp was steady. Also, when checking ECT I see the temperature jump so fast, started at 40F, then quickly climbed, within minutes was at 221F, and no harsh pressure on the hoses, something isn't making sense. I drove It in my driveway after I deleted all the codes and drove excellent. I am starting to think the ECM did initially have issues, no water damage anywhere. I will check fuses.

I did the hard reset by touching the 2 cables together for a while It started much nicer and. had no malfunctions, gauge temperature also went p gradually like it should without jumping to 235, which I believe was a fake glitch. I checked it with the scanner after it got to half line and it was 185. I drove it and was nice. then parked it and id the same thing it did yesterday "restricted performance" message and misfire. And smokes some, I think the coolant is getting into the cylinders. I put in the head gasket repair but not sure if it will take a while to fix it if it does. I did that a while back but never drove it before and only started it a few times. Will see.

oh and I got heat this time after I bed it again.

Which head gasket repair did you use?

Bar's leaks.

Okay, I know that Blue Devil can clog the heater core. I am not sure about bars.

I got good heat though, so I am not worried about that.

So do you have communication with the ECM now?

U0100 is still in permanent but not pending or current. Will check again. Am not sure whether the misfire is caused by the water getting in cylinders or just the ECM code when it pops.

Yep, try to clear the codes and see what happens. Did you find any fuses are grounds to the ECM that were bad?

No. The car was running great before changing coolant hoses and battery. No issues with misfires. Didn't touch any grounds, and doesn't seem like any were played with, no corrosions and nothing seems loose or damaged.

Does the security light flash when you try to crank the engine over? You might have had a voltage spike and took out the ECM. Let's check the power and grounds to see if the computer has failed. I have marked the power and grounds for you, please use a test light to test the circuits.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Check out the images (below). Please let us know what happens.

No issues with voltage and no, the light doesn't blink. Drive it today and came back then went out again and back and the temperature was still at close to super cold the all of a sudden started to climb till half. No thermostat in the car. Then drove it again and no misfires. Cane back and all of a sudden, the digital temperature needle started to go up so quickly all the way to high. Turned it off. Checked and the lower radiator hose is cold. Upper ones normal warm not hot, still strange that the lower stays cold after i removed the thermostat and flushed radiator.

Went back shortly after and read the codes but these could be from before. Also just started it and the temperature is in the middle. I saw the engine temperature on scanner now 103c.

So the ECM is communicating now? If so, start a new thread for the temperature issue.