I seem to remember posts in the past about this problem! Cannot find via search. Have had this fault on the same machine off and on for some time now, all sensors check out, and fault is intermittant. Today found machine actually faulty during visit...A3 copy paper z folded before the 2nd transfer roller! No burrs on guides, all sensors again working on input/output test. I swopped the registration clutch and sensor with those from the 2nd tray..and off it went no jams...for now? The J30-01 codes are recorded as being when feeding from any tray so not feeds...rollers and shafts etc checked and replace a few calls ago.