Has run alright, suddenly will crank but not start.

Any idea what ohms I might expect across the ECT connector terminals considering it goes through the PCM? I'm not trying to get rude or short with either of you, I only guess that the wire is not open from the PCM to the ECT due to the presence of the expected 5 vdc.

I already told you that the gauge shows midrange with the connector connected to the ECT (engine hot or cold), with it not connected to the ECT, and with the terminals jumped together (shorted back to the PCM as you suggested). I am glad you were online to help me, I think I got the best possible person, and I am trying to do and answer you the best I can. Is there anything I have not done or answered you? I cannot buy an ECT sensor until tomorrow, though if jumping the terminals makes no difference. Do you suspect that replacing the ECT sensor will change anything?

Looking at the wiring diagram in my chilton's manual, the PCM appears to be the only active component between the ECT and the temp gauge. I'm afraid the problem is in the PCM. It may have been a problem in the PCM since I bought the car, but something changed drastically yesterday. If it is not the temp circuit what else can I check?

Might it be the Crankshaft Position Sensor? If so, where is it physically located? Is it easier to get to from the top or bottom?

So the gauge may be disconnected from the PCM and this may have nothing to do at all with the car not starting? I found the PCM and there are a lot of wires on three connectors. All I know is the wires from the ECTS are black and yellow. I will track them down and post my findings tomorrow. Thank you for the info about the crankshaft sensor, I am learning more by the minute. I hope to hear back from you after I post again.

I do understand that the ECT is the sensor that provides a resistance to the PCM based on the temp of the coolant in the block, then the PCM regulates the other parts accordingly and display the appropriate reading on the temp gauge. I also understand if the PCM is not getting a resistance from the ECT, it will jump to just below mid-range and sit there. I found a pin out of the PCM connectors for a 1993 Saturn, but the wire colors do not correspond, so I'm not sure the pin #'s it says go to the ECT are correct, and I'm not sure which jacks are 1, 2, and 3. There are two blue connectors side by side and then only one brown connector is used and one empty.

It is a short. Bounes between 2 & 3 ohms.

With all 3 connectors off and measuring ohms from the black wire of the ECT connector bounces all over the place. From opent to 4 meg, into the kilo range and back around. Will not sit still.

7The wires do not line up with the 1993 PCM diagram I found. Not by color, nor by the wires being used in the connector. I'm pretty sure this car was originally a throttle body injection (vin 8) and a MFI engine (vin 7) was put in. I'm sorry I did not say that before.

Hi SaturnTech,
I took Christmas off of working on the car. I hope your Christmas was good. With all 3 connectors off the PCM, I measured voltage between the black & yellow wires, and from each wire to common and they were all zero. I suspect that is what they should measure with the other end disconnected. I did it with the key on and the key off with no change. I never could find the other end of the ECT wires at the PCM connectors.

FrankE.

I can tell you for sure it was a single cam engine originally and it now has a twin cam 16 valve engine. Could a different PCM configuration cause any of these problems? I think I can get a twin cam PCM from a U-pull it yard and see if that changes anything. It may be cheaper than taking it to a shop, which I may have to do after the new year to get this running in time for school to start.