I have a 1990 240 sedan I bought at the end of July for cheap because it wouldn't start. You can see my other posts about what the previous owner and I had done to it so far.

So I replaced the ECT sensor for the ECU, thinking that was the issue. A 30 year Volvo mechanic told me that the ECT sensor controls the fuel ratio before it enters closed loop. If it's sending the wrong signal it could flood the engine, like how mine was doing.
I tested the sensor and got OL so figured it was bad. I replaced it and it didn't fix it. I tested it at the ECU and it was still OL. So I figured it was a wiring issue. I got a brand new connector and wire and ran the wires to the ECU and the EZ116K. I spliced the new wires to the connectors, pin 13 on the ECU and pin 2 on the EZ116K. I tried to start it and it still wouldn't start.
I tested the same circuit again and still got OL from the ECU end. I had tested the wires before I installed them and outside the car they each got around 0.02 ohms, so I know the wires are good. Is there another ground on the engine that's bad, or did I get a faulty sensor from RockAuto?

 

You can tell if you have a faulty sensor by measuring the sensor directly.

I would always measure the sensor first to see if it is faulty. If you find the sensor is working, then ohm it out through the ECU connector. You should get the same reading. Are you sure you are probing the correct pin on the ECU connector?

 

yep. pull the ECT sensor's connector and measure resistance. you can google for a chart but a quick rule of thumb is the 300/3000 reference. A cold engine will be in the 3000 ohms range, a warm engine should be something less than 300 ohms. Most sensors fail as either open or shorted or fail to change with temp. So at room temp, I'd expect say 2700 ohms, drop the sensor into some boiling water and I'd expect something like 200 ohms