Dreame Robot Vacuum Error 4 — Cliff Sensor Block Fix

What Does This Error Mean?

Error 4 is a cliff sensor fault — the IR sensors on the underside that watch for stairs are blocked, dirty, or returning unexpected readings.
Wipe each sensor lens with a dry microfiber cloth.
If the robot keeps tripping Error 4 on a black rug or polished mirror floor, that's not a defect — IR cliff sensors confuse those surfaces with cliffs.
Block off problem floors in the app.

Affected Models

Dreame L10s Pro
Dreame L20 Ultra
Dreame W10
Dreame X20
Dreame D9

Common Causes

Dust or hair coating the cliff sensor lenses
Black or very dark floors absorbing IR (false cliff)
Highly reflective surfaces (mirror tiles) confusing readings
Sensor protective sticker not removed
IR emitter or detector failed (rare)

How to Fix It

Flip the robot.

Look at the front edge of the underside.
You'll see four to six small clear plastic windows — these are the cliff sensors.
They sit just behind the bumper.
Identify all of them before cleaning.
Wipe each sensor with a dry microfiber cloth.

Press the cloth against each sensor and rotate.
If they're particularly grimy, dampen the cloth with plain water — wring out so it's barely moist.
Avoid alcohol or window cleaner; over time those degrade the IR-pass coating.
Check for protective stickers.

If the robot is new or you bought it secondhand, look for any clear film over the sensors.
Each sensor should be clear or smoky plastic with no covering.
Peel any film away.
Test on a normal floor.

Set the robot on light wood, tile, or light carpet.
Press Clean.
If Error 4 doesn't repeat, the cause was the surface, not the sensors.
Use the app to set no-go zones over black rugs or polished mirrored floors.
Reset if needed.

Hold the power button for 10 seconds to reboot.
Power up and try again.
Persistent Error 4 with clean sensors on a normal floor means the IR module needs service — Dreame support is the next step.

Frequently Asked Questions

Why does the robot stop on my black hallway runner?

Black surfaces absorb infrared light.
Cliff sensors expect to see IR bouncing back from the floor — when little or no IR returns, the sensor concludes there's no floor.
This is a hardware limitation of IR-based sensing.
The fix is a no-go zone over the black runner.

Do newer Dreame models have better cliff sensors?

Yes — recent models with LiDAR or ToF sensors handle dark surfaces better.
If you have an older Dreame and a lot of black flooring, no firmware fix can change the underlying hardware.
You're stuck with no-go zones unless you upgrade.