The -40 indicates an open circuit on that sensors signal wire. If you check that wire with the engine on, I bet you'd see 5v there, which it should never see unless the circuit has an open. I'd start there, since it could probably cause a lean condition.
If you are on the right wire, there shouldn't be 5v on it with it plugged in. There is a 5v ref on the maf, so you may be on that one. I'll check a diagram and tell you which wire to check.
Almost all temp sensors on cars are negative temperature coeficcient thermistors NTC. As temp goes up, resistance goes down. Warmer equals lower voltage on these sensors, which is not what someone familiar with Ohms law would expect.
The ECM knows that the voltage on this circuit should never be 0v or 5v or it will set a normality code, knowing that the reading isn't normal.
Since you have a meter, we should b able to isolate this pretty easily after I check the diagram out.