I hooked up a scan tool and it’s showing the engine having a coolant temperature of -40 to +35 but most often around -20 even when warmed up. It’s almost 80 outside so I think a temperature sensor is bad. The temperature gauge works normally. How do I test the sensor and where is it? I see the sensor under the thermostat which I assume controls the gauge because when I disconnected it, the gauge stayed at cold. Does it also act as the fuel injection engine coolant temperature sensor? If so, how do I test it? Between the two wires or between each wire and ground? When warmed up the resistance between the two wires was about 330 ohms while between each wire and ground it was infinite. Is there a separate sensor for the fuel injection system?

 

The readings you got between the 2 wires is what you need to test.
The readings=80 Degress C or 176 Degrees F 300 Ohms.

But still seems like it would be bad to me reading off the computer.

The sensor feeds the fuel injections system as well.

 

Seems odd that if the temperature gauge functions normally that the sensor would be bad or the scan tool would show a low engine temperature. Anyway, I think I'll try substituting a resistor for the sensor that aproximates normal operating temperature. Say 250 to 300 ohms and see what the gauge and the scan tool shows

 

You might also want to check the thermostat and make sure it isn't broke.

 

Still the same low engine temperature readings. Noticed something real strange, as I accelerated, the temperature readings rose in proportion to how much I stepped on the gas. It would read +40 or +50F under moderate acceleration, and then back to -20F or -30F when I took my foot of the gas. The temp gauge is reading normally. Weird! Maybe electronic throttle needs cleaning or connector does too. But no codes stored relating to that.

 

Very weird like I said make sure the thermostat isn't broke.