1990 vette. My new coolant sensor still reads 100 before starting. Outside is 50 degrees. I am sure there must be a short. This is causing my car to start poorly in cold temperatures. I am using a scanner. What wire in the harness from the ECM to the Coolant sensor and which connector is it. The wire at the sensor has lost its insulation so I am not sure what color it is at that point.
Help is appreciated.
Not zooooooming yet!

 

Yellow is the 5 volt ECM reference; black is ground.

 

Sensor has only a one wire connector and there are two yellow wires out of ECM

 

Then your not looking at the Coolant Temp Sensor which is mounted at the front of the the intake below the throttle body. Like the gage sender (mounted in the right head), it's a thermistor meaning that it's resistance decreases as it temperature rises. The ECM provides a 5 volt reference and as the resistance drops, there's a voltage drop at the ECM. That drop is used to determine temperature and the ECM uses that to pulse the injectors. Higher voltages at the ECM - more pulse/fuel; lower - less pulse/fuel. In essence, it replaces a choke. Sensor ground (black) is spliced into/shared with the Manifold Air Temp Sensor and TPS. Unless the Coolant is actually 100 degrees, 100 from the Sensor is out of range on a 50 degree day (after it's sat overnight). Check for the 5 volt reference at the ECM and the Sensor Connector (disconnected for both). Disconnect the ECM harness and ohm out the wire to the connector. Examine the connector for corrosion on the terminals or a poor splice (new sensors often include a new pigtail which may have been poorly crimped to the harness). Plug another CTS into the harness and use your scanner to check the temp (no need to install it). If it's within a few degrees of ambient and the Manifold Air Temp Sensor, it's the installed sensor. If it's the same and the wires/connector check out, it's the ECM.