Replaced HG. Coolant temp gauge, Coolant temp sensor NOT WORKING.

[DallasN2O]

Coolant temp sensor is reading -74f according to logger.

Gauge on the dash is not working either.

Both are hooked up.

Any tips? I've done my best to check for breaks / shorts in the wire, don't see any.

Do these have a common ground that they need in order to function?

Both were working fine before i replaced the HG.

 

[luv2rallye]

Note that dash gauge uses the 1 wire ECT sensor while ECU uses the 2 wire ECT sensor. Try grounding the 1 wire sensor's wire (yellow-green), turn key on, gauge should go to highest. This should tell you if the gauge is working. The sensor itself should read 104 ohms (+/- 13.5) at 158F. It increases resistance with lower temps.