What does solenoid defective mean in a 1997 Plymouth Breeze?

It has 147,586 miles on it and it is a 2.0 4-cylinder motor in it. I recently put a motor in it (a salvage one) and about a week after it put it in, the check engine light came on. I took it to Auto zone to see what it meant. It said that there was a leak detection pump defective and that there was a soleniod defective. It also said that that the EMC detected the leak detection pump switch did not change after the soleniod was energized. I have NO clue what any of that means. Im just not sure what to do at this point and I would really appreciate any help I could get. Thank you.