I'm having the same problem as a lot of you I guess. My Jeep would start fine, but then after a little while of driving or idling it would sputter then shut off! Even after that there was NO Check Engine Light that came on. I already replaced the plugs and the Throttle Position Sensor since that is what I thought it would be by searching this forum... but then the CEL cam on and it threw those two codes. I searched here and found out that P0340 was Camshaft Position Sensor, so I guess I'll have to replace that. On the sheet that shows me what P1391 is, I still can't figure out what it means.
Definition: CMP or CKP signal intermittent condition
Explanation: The ECM detected the actual CMP position disagreed with the expected CMP level
Probable cause: 1. Timing belt or chain stretched or jumped. 2. Defective CMP sensor
What is CMP? What is CKP? My guess is Camshaft and Crankshaft? So by replacing the Cam Pos Sensor, this will fix my P1391?