Konica Minolta C2557 — Toner density/replenishment fault

What this error means

The toner concentration in the developing unit drifted out of range — classically after running toner fully empty, using non-OEM toner, or developer end-of-life. One of the most common bizhub service codes.

Symptoms

• Faded prints before the error
• Appears around a toner change

Try this first (safe DIY steps)

1. Reseat the toner bottle; confirm exact OEM part for your model
2. Power cycle once
3. Do not repeatedly reset — running the replenishment cycle against a real fault can worsen developer damage

Safety: power off before any physical intervention. Never bypass covers or interlocks — fuser areas run hot enough to burn.

When to call a technician

Almost always — a power cycle alone usually does not clear C2557. It requires a service-mode trouble reset plus a toner-density (TCR) auto-adjustment, and often developer service. Book the call rather than fighting it.