I am getting code 42 & code 72 on the check engine light in my 1996 Jeep Cherokee Sport with the 4.0L engine. The thing is, nothing appears wrong with the way the Jeep is running. I am getting no stalls, misfires, or no starts at all. I have checked all fuses, none are bad, and I'm just puzzled. A month ago, I was getting this code and was also occasionally getting a starter sticking on at start up. I did a lot of research then and decided to replace the ASD relay, ignition switch, and starter to try and knock out the code 42 and fix the starter issue. About a week after driving it, it's my daily, code 72 for the catalytic circuit returned but no code 42 for the ASD circuit. I thought, I've resolved it! Now code 42 has returned with code 72 this week. I'm puzzled and don't know where to go from here because the darn thing is running just fine. I Seafoamed it last night just to clean the fuel system. Help please!