Where was it suggested that resetting the OBD would do anything?

I explained why you are getting readings other than expected. The 2 wires are signal and low ref with 5 v on the signal and the sensor is a variable resistor. In other words: measuring voltage across the pins does not tell you anything.

And that the problem is probably related to a short to voltage. Since it reads high when the sensor is disconnected that leads me to think melted wire or bent pins or bad ECM. But I'm not sure how it should read when disconnected. I do know it should never read above 5 volts (4.8 nominal).

I must have been looking at the wrong schematic earlier. The tan wire goes to pin 4 the yellow goes to pin 58 on ECM X2 connector. I think that is the lower connector.

 

By resetting , I mean that I cleared the code with the scan tool. The voltage reading was across the pigtail disconnected from the sensor.
I just disconnected the ECM connectors with the key off and now I have a bunch of codes
P0118 P0335 P0353 P0222 P0122 P0443 P0013. This car is killing me!
I'm going to disconnect the battery for a while and see if that corrects things.

 

Yes a battery lobotomy may help, and the correct thermostat as mentioned AC Delco 131-158 180 degree

 

Just an update this morning, I had the battery disconnected overnight to see if those multiple codes would be removed.
No such luck. I only removed the connectors on the ECM ( with the key off),to take pictures of the terminals. I did find that the yellow wire from
the sensor is not on pin 48 but a yellow wire is on pin 45. Either way, my meter shows an open on this wire. If there is away to clear these codes
I would like to know. The engine ran fine, considering the adjustment for the sensor issue before this and now it runs like crap.
I need help! My wife wants to get rid of this car, but if it is something I am overlooking here. I checked fuses for the ECM and they are good.

 

Added a few more codes, p0340, P0122, Tach not working. Swapped previous ECM back in and same issue.
Seems like power or some main circuit not working on ECM.

 

I checked all those codes they have one possible cause in common, wiring ! Have a look for chaffed wires under the purge valve on the driver’s side of the engine, check all ground wire connection points , are they clean and tight?
In you case where you disconnected the ECM check that connector for bent and loose pins.

 

I checked for chafing and found a bare spot on the knock sensor wiring, which I isolated. computer connections look good. Opening up some access to the wiring looms to check wires.
Any where I can find a schematic or pin out for both ECM connectors so that I can trace them out. I am sure something must have an opening in the ground lead common to all these sensors.
My wife wants me to throw in the towel on this one. The car just ran and road so well for 292,000 miles!

 

Attached is a pdf of the 2 connectors.

 

Thanks a lot Don! You Da MAN! This should help immensely!

 

I was able to determine that the ECT sensor wiring/pigtail is bad. Also, with the other codes, the 5 volts to intake camshaft pos. sensor was a bad connection at the ECM connector. Repaired the connection.
Now I am looking for the Crankshaft position sensor wiring.. According to the diagram, pion no. 45 Yellow wire is CKP Sensor 1 Signal. Not sure which is the 5 volt supply. Pin 54 L-GN 5 volt reference seems to be it. Would this be correct? I think there may be some loose connections between the ECM and the terminals.