Is there any way with a Digital Multimeter or other device to test the Coolant Temperature Sensor? I have a hunch mine is bad, but being a Holiday the parts stores and closed and I'd rather not replace the sensor unless I needed to. I suspect the resistance changes on the sensor depending on temp, but does any have any idea what the range is? I am also getting a code 45, which I am thinking could be related to the computer not knowing what the engine temp is. This is for a 1989 Firebird w/ the 2.8.

Don't know if you found your answer somewhere else or not, but you can do a resistance test on the CTS to find out if it's good or not. But, you have to do it with the engine cold and the coolant at ambient air temp so you know whereabouts the resistance should read. At 70*F, the sensor should read around 3400 ohms. As temp increases, resistance drops. I would think that the reading should be close to the same as for the IAT in the air cleaner, so maybe testing that as well would give you a ballpark of where the CTS should read.

Thanks, I did what I could to test it at cold and then warm, however I was have a hard time getting good readings with how buried the sensor is. I am trying to get Tuner Pro RT to connect so I can just see the values it thinks it is getting to match with the resistance that I found. From what I can tell the resistance just dropped off the bottom when it got warm. It never made it up over 180ish so I am suspecting that the sensor is reading wrong.

If I can't get my laptop working with the car I will just get a pigtail to make it easier to test the resistance.

Wit ha few mods like removing the AC rad in the way, a good air dam and a fresh air intake mod, you won't see temps much higher then 180 uniess it sitting still without the fan running.

The main reason I am trying to test the CTS is because the car is getting up to ~220 during normal highway driving. I left the car just sitting the other day until it was reaching 240 and the fan never kicked on. The fan is working so I am trying to figure out why it isn't turning on when the car is getting that hot.

Well it shuoldn't get that hot moving. Check your air dam.

The only time my fan need to come on is if I sit still for a while, like ina long bank or fastfood line. Stop lights no problems. Which eman the fan doens't come on but a few times a year.

Yeah, I am pretty sure the reason it is getting to that temp is because the bottom of the front nose has actually been worn through by sharp inclines and has separated. I think I am getting part of the nose bending down and blocking airflow to the radiator. The car just acts funny in general with the fan it has seemed since I bought it, I'd just like to figure out what is going on with it. It's nice to just be able to see if the car is commanding the fan to turn on and what it is thinking.