HP Designjet Z5400 PostScript ePrinter isn't sensing I've loaded paper

[Roseanna777]

I bought a gently-used HP Designjet Z5400 but upon taking it home and attempting to print, I'm having an issue - despite the rolls of paper being loaded correctly (followed the manual set up instructions as well as display instructions to a T) the printer is not detecting/grabbing/feeding either rolls of paper or sheets. It seems like a sensor issue, but I could be mistaken.

Troubleshooting I've already attempted:

1. Load Roll 1 and Roll 2 using display instructions - Display menu stays at "Feed paper from roll 1" though I've already done that. Paper cannot be fed in any further without lifting blue lever (which doing so cancels loading and requests you remove the paper)

2. Loading a sheet using display instructions - Similar results: Display menu says "Place sheet in input tray" though I've already done that.
1. Turning it off an on again - same issue

2. Ensuring firmware is up to date - it says it is

3. Restoring factory settings - no change

4. Ensuring paper is loaded on the roll properly - it is.

5. Ensure printer is not pressed up against wall - it's not.

I'm running out of ideas. Set up instructions say once you feed the roll into the printer should grab/feed, measure paper, and check alignment. It does none of these things. Help??

[Repairatrooper · Accepted solution]

Could be a failed oops. (out of paper sensor). This sensor is in the feed path and located on right side of the paper path. You can likely find a service manual online for this printer and that will give you some great troubleshooting tips.

[Roseanna777]

You were right! I did find the service manual online, ran a sensor test in diagnostic mode to confirm that's what was failing, and followed it's instructions on how to replace it. I got most of the way through removing parts when I saw the sensor had come unplugged (in the move apparently as it's wire is tucked up under the bottom of the printer but the cable is partially exposed). I plugged it back in and reassembled and now it's working like a charm.

Thanks for the response!