Centauri Carbon: leveling error 502 (leveling sensor data collection error)

Symptom

During automatic leveling on the Centauri Carbon, the nozzle probes the same spot again and again or keeps pressing down on the plate, and the screen shows code 502 «leveling sensor data collection error»; leveling is interrupted.

Likely causes, from most to least likely

1. The printer stands on an unstable or uneven surface, for example a table on wheels or one that wobbles.
2. The bed locking screws have come loose.
3. The bed is tilted: the three joints between the bed and the Z lead screws are not at the same height.
4. A connector on the pressure sensor adapter board is loose.
5. A pressure sensor or the adapter board is faulty.

Checks to tell which one it is

• Check that all four feet are fully on the table and the printer does not rock; if in doubt, test with the printer on the floor.
• After homing, measure with a ruler or caliper the distance between each of the three Z-axis mounting blocks and its joint with the platform: they must be equal.
• Note at which spot the nozzle stops or presses down: it helps to find the faulty sensor.

Before you start

Before taking anything apart, cleaning or adjusting it, switch the printer off and unplug it, unless a step says otherwise, and do not touch the nozzle, the heater block or the bed until they have cooled down. If in any doubt about electricity, heat or moving parts, stop and ask a professional.

Step-by-step fix

1. Put the printer on a firm surface

   Place the printer on a flat, stable surface with no wheels and all four feet resting. If you are unsure, repeat leveling with the printer on the floor.

   Check: Leveling finishes without error 502.

   If that does not fix it: Check the locking screws (next step).

2. Tighten the locking screws

   Remove the PEI plate. On each of the four sets of locking screws, hold the upper screw with one Allen key and tighten the lower one clockwise with another.

   Check: No set of screws is left loose.

   If that does not fix it: Check the bed tilt (next step).

3. Correct a tilted bed

   Refit the PEI, home the printer and measure the three Z mounting-block distances. If they differ, follow Elegoo's guide to adjust a tilted bed: with the printer off, unplugged and on its side, remove the bottom cover, take the Z belt off its pulley, press the three lead-screw joints down to the bottom, refit the belt and tension its tensioner. Then run the full self-check.

   Check: The three distances are equal and the self-check passes.

   If that does not fix it: Check the sensor connectors (next step).

4. Check the pressure sensor connectors

   With the printer off and unplugged, remove the bed following the first steps of Elegoo's guide for replacing the pressure sensor adapter board, then unplug and reconnect the five connectors on that board. Reassemble and repeat the auto-leveling calibration.

   Check: Leveling completes without code 502.

   If that does not fix it: Locate the faulty part (next step).

5. Find the faulty sensor

   With the bed removed, disconnect the four connectors Elegoo indicates and swap their positions within the same row (never diagonally or between rows). Refit the bed and level again.

   Check: If the spot where the nozzle stops or presses down changes, the pressure sensor is faulty; if it does not change, the adapter board is.

   If that does not fix it: Contact Elegoo support with a video of the error, a photo of the table, the Z mounting-block measurements and the results of these tests.

Prevention

• Keep the printer on a firm, level surface without wheels.
• Check the bed locking screws from time to time.

Still not fixed?

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Printers it applies to

Elegoo Centauri Carbon.

Official sources

This guide summarises the official documentation linked here:

• Error 502: Leveling sensor data collection error · Elegoo
• How to Adjust the Tilting Hotbed · Elegoo