Mistake 4 on Xiaomi robot vacuum cleaner: a complete guide to elimination

Xiaomi’s robot vacuum cleaners have become an integral part of smart homes, but even the most reliable appliances sometimes fail.One of the most common problems is Error 4, which appears on the display or in the Mi Home mobile app. This bug can completely paralyze the device, causing users to panic to look for a solution.

Unlike other fault codes, error 4 is often associated with mechanical problems or navigation system failures. It can appear as new models (Xiaomi Robot Vacuum-Mop 2 Pro, S7 MaxV Ultra and older (Mi Robot Vacuum) 1S). In this article, we will discuss all possible causes of error, diagnostic methods and step-by-step instructions for elimination - from simple actions to complex technical manipulations.

It’s important to understand that ignoring this error can lead to more serious breakdowns, so we need to act quickly. We’ve gathered information from Xiaomi’s official manuals, user feedback and advice from service engineers to offer you the most complete guide.

What does Error 4 mean on Xiaomi’s robot vacuum cleaner?

A code 4 error in Xiaomi’s robot vacuum cleaners signals problems with the side brushes or drive system, described in the manufacturer’s official documentation as “side brush malfunction or blockage.”

• 🔧 Physical blockage – hair, threads or debris piled on the axis of the brush
• ⚙️ Wear of the mechanism - erased gears of the drive or the brush itself
• 🔌 Electrical Failure – Damage to Wiring or Contacts
• 🤖 Firmware failure – false alarm of the sensor due to a software bug

Interestingly, the error can be different on different models, for example, on Xiaomi Mi Robot Vacuum-Mop P, when error 4 occurs, the robot completely stops and emits an audible signal, and on the other hand, the robot will be able to make a complete stop and make a sound signal. S7 can continue cleaning with the main brush, but with a constant notification in the application.

The manufacturer recommends that you start your diagnosis with a visual inspection of the side brushes, but in practice, in 30% of cases, the problem lies deeper — in electronic components or firmware.

Primary Diagnosis: What to Do When an Error 4 Appears

Before disassembling the robot or carrying it to the service, perform a basic check, which in 60% of cases helps to fix the problem:

1. Turn off the robot with a long press on the power button (5-7 seconds) and remove it from the charging station.
2. Turn the device over and look at the side brushes: 🧶 Wrapped hair/threads on the axis of the brush 🔄 Free rotation of the brush with the hand (should be light, without jamming) 🔍 Integrity of plastic parts (cracks, chips)
3. Remove the side brushes by pressing the locks on either side: 🧹 Clean seats ⚙️ Condition of the gears of the drive (are not the teeth erased) 🔌 Contacts of connectors (are there oxidation)

Put the brushes back in and turn the robot on. If the error is gone, the problem was mechanical.

If you've had error 4 after this manipulation, move on to a deeper diagnosis (LDS) Error 4 is sometimes caused by a conflict with the navigation system after a firmware update, a nuance often overlooked.

Turn off and restart the robot|Examine the side brushes for blocking|Check the free rotation of the brushes|Clean up the landing places from garbage|Check connector contacts-->

Mechanical causes of error 4 and their elimination

In 70% of cases, error 4 is related to mechanical malfunctions, and let's look at the most common problems and ways to solve them:

1. Pollution or blocking of brushes

This is the most common reason, especially if the robot is used to clean long hair or animal hair, and the hair is wound on the axis of the brush, creating resistance, which the sensor perceives as a malfunction.

Decision:

• 🧼 Remove your brushes and clean them thoroughly from the coiled hair.
• 🔪 Use tweezers or scissors to remove tightly wound hair
• 🧴 Wipe the brush axis with alcohol to remove sticky residues

Wear or breakage of brushes

Side brushes are consumables. On average, they're enough to keep you clean. 6-12 months of active use, signs of wear and tear:

• 📉 Reduce the length of villi by more than 30%
• 🔄 Uneven rotation (brush "beats" when working)
• 💥 Cracks on plastic base

Solution: Replace brushes with original or compatible. For Xiaomi models, brushes with articles are suitable. ZSTN0466NM (for most models; or ZSTN0565NM (series S7 newer).

Problems with brush drive

If the brushes are clean and intact, but the error remains, the problem may be in the drive mechanism.

• ⚙️ gears of the gearbox (dentures are washed)
• 🔗 Connecting shafts (bending or breaking)
• 🛠️ Bearings (jammed from dust ingress)

To diagnose, you need to disassemble the bottom cover of the robot. 1S and S5 You can do it yourself by unscrewing 4 screws (S7, Vacuum-Mop 2 Pro will require a special Torx screwdriver T5.

⚠️ Warning: When disassembling the robot, be careful with the tape LDS-The damage to the navigation module will require a complete replacement, which will cost you a lot of money. 30-50% cost of new device.

Electronic causes of error 4 and their elimination

If the mechanical part is fine, but error 4 keeps coming, the problem is the electronics.

1. Hall sensor malfunction

Hall's sensor is responsible for controlling the rotation of the brushes, and if it breaks down or gets dirty, the robot thinks the brushes are locked.

• 🔄 The brushes are rotating, but the error remains
• 📱 The application shows the incorrect speed of rotation.
• 🔧 The error occurs periodically, not constantly.

Decision:

1. Clean the dust sensor with compressed air
2. Check the integrity of the wiring to the sensor
3. If necessary, replace the sensor (article) ZSTN0478HM most models)

2.Control of management fees

The board may fail:

• 🔥 Resistors in the brush supply chain
• 🔌 Sensor connection connectors
• 🛠️ Motor driver chips

Diagnostics board requires special equipment (multimeter, oscilloscope). If you do not have experience with electronics, it is better to contact the service — 1500-3000 ruble.

3. Firmware conflict

After the firmware update, some users experience a false positive of Error 4. This is due to bugs in firmware, especially on models with laser navigation.

Decision:

• 🔄 Reverse the firmware to the previous version via Mi Home (if available)
• 🔧 Reset the settings to factory (Settings) → Reset)
• 📱 Reinstall the Mi Home app and re-add the device

⚠️ Note: On Xiaomi models with firmware newer 3.5.8_003006 No rollbacks through standard means, and then only flashing through ST-Link in the service center will help.

Step-by-step instructions for disassembling the robot to eliminate error 4

If you decide to disassemble the robot yourself, follow this instruction. We will consider the process using the example of Xiaomi Mi Robot Vacuum. 1S — one of the most popular models:

Tools required:

• 🔧 Screwdriver cross (PH0)
• 🔨 Plastic mediator (to open latches)
• 🧲 Magnetic screwdriver or tweezers (for small screws)
• 📸 Smartphone to photograph the process (so as not to confuse the details)

Procedure:

1. Turn off the robot and remove the dust collector.
2. Turn the device over and unscrew the 4 screws on the bottom cover (they can be hidden under stickers).
3. Carefully tuck the cover with a plastic mediator, starting at the back (from the charging contacts).
4. Disconnect the connectors of the side brushes and remove the module with the motors.
5. Check the gears, and if they're working, the teeth should be sharp, without chipping.
6. Check the integrity of the wires going to the Hall sensor (a thin black wire with a white connector).
7. Collect the robot in reverse order, making sure all connectors are tightly connected.

On models S7 And the newer disassembly process is more complicated because of the extra wet cleaning sensors, and if you're not sure about your abilities, you better contact the service — 500-800 ruble.

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Before disassembling the robot, take photos of the location of all connectors and screws, which will help to avoid errors during reverse assembly and save hours on finding "extra" parts.

When to contact the service: signs of serious malfunctions

Not all breakdowns can be repaired on their own, but here are some signs that your robot needs professional help:

• ⚡ Error 4 appears immediately after turning on, even if the brushes are removed
• 🔥 The robot smells like a smoldered plastic or a smelted fire.
• 💥 When trying to rotate the brushes, foreign sounds are heard (screaming, crackling)
• 📵 The robot does not respond to resetting settings and flashing
• 💧 On the board, traces of oxidation or staining are visible.

Average prices for repairs in service centers:

Before contacting the service:

1. Make a backup of the cleaning card in Mi Home (if possible)
2. Take a photo of the serial number (under the dust collector)
3. Check if the service center has access to original Xiaomi parts

⚠️ Note: Unofficial service centers often use unoriginal parts that can fail through the use of unoriginal parts. 1-2 Official centers of Xiaomi in Russia can be found on the website service.mi.com/ru.

Error Prevention 4: How to Prevent Reappearance

To prevent error 4 from reappearing, follow these guidelines:

1.Proper brush care

• 🧹 Clean your side brushes after each cleaning
• 🚿 Wash them with warm water once a week.
• 🔄 Change your brushes every time. 6-8 months

2. Optimization of cleaning conditions

• 🧶 Remove long threads, laces from the floor before cleaning
• 🐕 For homes with animals, use robots with enhanced wool cleaning mode (S7 MaxV Ultra)
• 🚪 Limit areas with high pile of carpets

Programme prevention

• 🔄 Update your firmware regularly (but not immediately after release – wait for it to come out). 1-2 weekly bug-in-the-moment)
• 📱 Once a month, reset the cache in the Mi Home app.
• 🔧 Use alternative firmware (e.g. Valetudo) for advanced diagnostics

For models with a wet cleaning function (Vacuum-Mop 2 Pro), it is especially important to monitor the condition of the sealing gums around the electronic components.

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Regular brush cleaning and timely replacement of consumables reduces the likelihood of a 4 error by 80%, and most "serious" breakdowns begin with non-compliance with basic maintenance rules.

FAQ: Frequent questions about the error 4 on Xiaomi robot vacuum cleaners