after scanning my car with TunerPro, I discovered that my coolant temperature sensor is not working properly. it reads -39.99 deg C. i tried swapping the sensor, and i get the same results. this makes me think the wiring to the ECM might have issues.

i disconnected the connector, took a multi-meter and stuck the probes in the harness end of the connector. it read 4.5kohms. i'm not 100% sure what the means... but the fact that i got a signal at all means the wire is continuous, right?

what else can i check to figure out why i cant get that sensor to read properly?

 

I might be reading it wrong, but in order to test continuity, you need to stick one probe in the sensor end of the wire, and one in the PCM side of the wire. Then, if it reads any ohms, the wire isn't broken.
I had this same problem on my '82, but i fixed it by swapping sensors. you could always try taking the new one back and exchanging it, it could still be bad. new just means shiny.

 

Like he said,check the wire from both ends.If you did and got that much resistance something is wrong in the wire.Check the wiring diagram for connections between the ends.On one of mine i found a bad connection in the c100 plug on the firewall.as soon as i put it back together the problem was solved.A high resistance doesn't mean it has to be the wire.If your wire is bad it will most likely be near the engine where the vibration is highest.The wire will eventually break when moved enough.

 

since my multi-meter obviously wont reach between the ECM and the sensor connector, i'll just have to extend it using a speaker wire or something insultated like that? i've never actually accessed the ECM before, althought i know where it is. will i be able to directly probe where the wire connects? or would i have to somehow remove it from the harness?

since i'll be adding that many feet of wire, i guess the resistance is irrelevant as long as i get a signal at all.

 

You can always leave the sensor hooked up and measure the resistance on ECM pin C10 (yellow wire) on connector C2 (the big black one). Measure the resistance against ground with the C2 disconnected. You should see a few kiloohms (3-5kohms).
Then measure the resistance between the pin C10 and pin D2 (black wire). You should see the same resistance as before.

Then, remove the CTS connector and ground the yellow wire. Go back to the ECM and measure the pin C10 again. It should read 0 ohms.

Don't bother checking the C100, the CTS yellow wire does not go through there. It comes into the ECM through the passenger side fender and behind the kickpanel.

Hope this helps.
Lou