Have a question about the lead that goes to the temp sensor. I have 5 volts on one side of the lead, and 4.5 volts on the other side of the lead. Seems strange that I would have voltage on both sides of the lead. I thought one side would be reference voltage, and the other would go to the computer so shouldn't be much of any reading on the computer side. I tested with key on and the lead disconnected. 1990 Volvo 740GLE DOHC motor. Cheers

 

Test with lead connected. Then you will get a voltage drop over the sender. You will get a larger drop when the engine is cold (higher resistance) and a lower voltage drop when warm (lower resistance)