I have a strange issue with my 98 XJ. The check engine light came on after having crankshaft bearings, rear main seal, timing chain and NSS all replaced. The light stays on for 1-3 days then goes off for 1-2 days then back on. I had my technician check for codes but there no codes at all. Jeep runs great though. Maybe a little rough until it warms to operating temp. It seems very random except for it continuing. My tech is stumped too. Has anyone on here ever run into this issue?