Pin 1 is ground, pin2 is NVLD switch signal and pin 3 is NVLD solenoid control. NVLD stands for natural vacuum leak detection. As the vehicle cools, the fuel tank naturally contracts creating a vacuum on a seal container. When this occurs the switch closes in the NVLD signaling to the PCM there is no leak.

This is what a 2004 Caravan has. A LDP is used on older vehicles and actually builds pressure in the evap system and monitors time to determine if a leak is present.

Newer vehicles use an ESIM, emission system integrity monitor.