Try DIY first — may need a proVerified by FixOffice
Ricoh SC390 — Toner density (TD) sensor error
Applies to: Aficio / MP / IM series
What this error means
The development unit's toner density sensor is reading out of range — commonly after toner runs fully empty, a non-OEM toner issue, or developer end-of-life.
Symptoms
- Faded or patchy prints before the error
- Appears after a toner change
Try this first (safe DIY steps)
- Reseat the toner cartridge; confirm it's the correct OEM part for the model
- Power cycle once
Safety: power off before any physical intervention. Never bypass covers or interlocks — fuser areas run hot enough to burn.
When to call a technician
If it persists — developer unit service and sensor recalibration.