Canon iPF5100 false jams and E161-4050 error

[pebkac]

I've got a Canon imagePROGRAF iPF5100 that was brought into the shop for an error code, E161-4050, which is not in the service manual. Apparently it has something to do with ink non-ejection (ref). The user mentioned they had some kind of trouble with the left printhead, so we replaced that first. No change, the error still reappears during startup cleaning and drop detection.

Supposedly you can print a nozzle check from service mode, which skips cleaning and drop detection. However, the device throws a paper jam error every time it feeds paper. Paper is loaded up to the platen, the printhead moves over, and it stops with a jam error. It jams from both tray and roll. The paper feed sensor (just behind the platen) is working, and that seems to be the only sensor both paper paths have in common. I thought maybe the optical sensor on the carriage wasn't seeing the paper edge or something, so I replaced that sensor. No change.

I'm a bit stumped. I'd like to address the paper feed issue first, so I can troubleshoot the other.

Has anybody run into either of these things before?

[blackcat4866]

The only real incidence of "jam, can't clear" was on a Kip wide format. There was a 25mm by 91cm long trimming laying in the paper path atop one of the three possible paper feed switches, but totally inaccessible without disassembly. The only clue was the outline of white paper seen through the teardrop shaped cutout in the upper guide plate, where I should have been seeing the tip of the flag. That's what I would look for. =^..^=

[pebkac]

This jam isn't persistent, it just occurs with every feed. Once a sheet stops at the platen the printer knows its there and won't continue until I remove it. Once I pull the sheet out and tell the printer to continue, it will merrily go about its business picking up the next page and feeding it to the platen, where the fun starts again.

I'm starting to wonder if both the ink ejection and jam errors are caused by a carriage or trailing cable issue. However, I have plenty of experience with Canon's smaller inkjets, and those types of problems just don't happen.