I have a 94 Ranger, and the check engine light came on a while ago. I checked the system and one code was a faulty EGR pressure sensor valve. I replaced it, and the light stayed off. Another code that was throwing the light on was A/C on during self test, but the A/C wasn't on at all when I checked the system. The light still comes on when the air is on. What could be causing this? What do I need to replace? Thanks