Hi, you have an E36 or E30 ECU ?
For the temp sensor you certainely have an electric probleme. I have an E36 temp sensor and it work. The only difference is the indicator position.
With E30 sensor, hot engine, the indicator shows 1/2 (12h). With E36 sensor it shows 1/4 (10h).
You can't inverse the two connectors because the first as two pins et the second only one.