I've been having a really hard time with the coolant system on my 99 Accord EX (5 speed). The coolant gauge stays on C and might move a tiny bit if I'm sitting in traffic. I started digging into the cause of this and have came up short. I put in a new OEM thermostat and a new ECT sensor. I noticed the connector that goes to the ECT had bare wires showing so I connected a new one. I tested the voltage at the connector and it read 5.06v with good continuity on the ground. I used my cheap scanner to look at a graph of the ECT temp being reported on the PCM and it went from 56°F to 112°F in 10-15 minutes of idling. Obviously it's supposed to report a lot higher than that so I believe it has to be a computer issue at this point. If I unplug the ECT it reads -40°F so I'm pretty sure the sensor is working and it's new. My question is should I test the PCM connector to see what the sensor is reporting back to the PCM or could it be another problem? Also my heater doesn't blow hot air and all of the radiator hoses heat up to the point where I don't even want to touch them so I know it's not 112°F.

Update: So I pulled out my IR thermometer and ran a test which leaves me even more confused. With the bleeder kit installed I let the car idle on a hill, just in case there was air still trapped in the system. I let it idle for a minute until it hit about 160°F then I turned the fan on to see if the coolant was flowing through the heater core. The coolant temp dropped to about 135°F so I think it's going through the heater core correctly. Also I replaced the heat core on this car already so I know that shouldn't be the issue here. I turned down the heat to the 1st setting so the car could get all the way to operating temp. The temp normalized and went up to 195-200°F or around there and the radiator fan came on like I should. So everything seemed to be working but on my OBD2 reader it says the ECT is 100-110°F which makes zero sense. From what I understand the radiator fan comes on when the ECT sensor reads 200°+ or whatever its programmed at. So how are my radiator fans still working if the car thinks it's at 100°F. After this test I believe it has to be the PCM at this point I've changed just about everything else. I attached some pictures of temp readings and the OBD2 graph.

Maybe it could be a wiring issue but I'm not sure on how to test the PCM currently so if anyone knows that would help a lot.

It's almost like it's reading half of what it's supposed to idkkkk