Error E21 on a Bosch washing machine: a complete analysis of causes and solutions

Error E21 on the washing machine Bosch - one of the most common problems faced by owners of equipment of this brand. It signals a problem in the water drainage system, but its true causes can vary from a simple blockage to serious breakdowns of electronic components. In this article we will look in detail at what exactly the code means. E21, how to independently diagnose the problem and what steps to take to eliminate it - from simple manipulations to complex repairs.

It is important to understand that ignoring this error can lead to more serious consequences: from pump failure to damage to the control board. Moreover, in 30% of cases the problem is solved in literally 10 minutes without calling a technician. We have collected proven elimination methods E21, relevant for models Bosch 2018–2026 model years, and also added tips from service engineers that save time and nerves.

If your car stops with a code E21 on the display or the corresponding combination of indicators is flashing (for models without a screen), do not panic. By following our step-by-step instructions, you can determine the root of the problem and choose the best way to solve it - be it cleaning the filter or replacing the pump.

What does error E21 mean on Bosch?

Code E21 in washing machines Bosch stands for "problem with water drainage". The diagnostic system detects that water does not leave the tank within a specified time (usually 8-10 minutes after completion of the wash or rinse cycle). In this case, the machine can:

• 🛑 Stop work and block the hatch
• 🔄 Focus on the "Drain" mode
• 💧 Leave the water in the drum or tray
• 🔊 Make a buzzing or clicking sound without rotating the pump

Unlike the error E18 (problems with water supply), E21 always associated with the inability to pump out fluid. Moreover, it may not be only the pump that is to blame: blockages, faulty sensors, or even software glitches are often the culprits. For example, in models Bosch Serie 8 with the system EcoSilence Drive the error sometimes occurs due to a firmware conflict with the drain control module.

Interesting fact: in cars Bosch before 2020 release code E21 could appear due to overheating of the pump motor, while in new models the diagnostic system separates these errors (for overheating it is used E23). This is worth considering when looking for the cause.

⚠️ Attention: If there is an error E21 appears immediately after turning on the machine (before the wash starts), this may indicate a malfunction of the control board or water level sensor. In this case, independent repairs without diagnostic equipment may aggravate the problem.

The main causes of error E21

Reasons for the appearance of the code E21 more than a dozen, but 90% of cases come down to five key problems. We have arranged them according to frequency of occurrence - from the most likely to the rare:

Reason	Signs	Difficulty in eliminating
Clogged filter or drain hose	There is water in the drum, the pump hums but does not pump	⭐ (you can fix it yourself)
Malfunction of the drain pump (pump)	There is no sound of the pump, the error appears at the draining stage	⭐⭐ (part replacement required)
Problems with the water level sensor (pressostat)	The machine “does not see” the water in the tank or does not drain it completely	⭐⭐ (need diagnostics with a multimeter)
Blockage in the pipe between the tank and the pump	The water leaves slowly, gurgling sounds are heard	⭐⭐⭐ (machine disassembly required)
Control board failure	The error appears chaotically, accompanied by other codes (E16, E18)	⭐⭐⭐⭐ (specialist needed)

Filter and pump blockages are especially common in houses with an old plumbing system, where there are many impurities in the water. In such cases, it is recommended to install additional coarse filters at the entrance to the machine. For models Bosch Serie 4 With vertical loading, there are problems with the nozzles due to their curved shape - lint and threads accumulate there.

One more nuance: if there is an error E21 appeared after moving or changing the location of the machine, check the slope of the drain hose. According to the instructions Bosch, it must rise to a height of at least 60 cm from the floor before connecting to the sewer, otherwise the water will flow away by gravity and the pump will not be able to create the necessary pressure.

Step-by-step diagnosis of error E21

To pinpoint the cause E21, follow this algorithm. At each stage, check whether the error disappears after the following steps:

1. Check the drain hose for kinks and blockages

2. Clean the pump filter (bottom panel at front)

3. Perform a test drain manually (Drain/Spin mode)

4. Check the pipe between the tank and the pump

5. Diagnose the pump with a multimeter (winding resistance 150–200 Ohms) -->

Step 1: Check the drain hose

Disconnect the hose from the drain and check it for kinks or blockages. The easiest way is to blow into it: if the air flows freely, the problem is not in the hose. In models Bosch Maxx The hose often gets pinched when the machine is installed close to the wall.

Step 2: Clean the pump filter

The filter is located in the lower right corner behind a small cover. Carefully unscrew it (up to 0.5 liters of water may spill out!) and remove debris: coins, buttons, threads. In 60% of cases this is enough to eliminate E21. After cleaning, check whether the pump impeller rotates - if not, the pump is faulty.

Step 3. Test drain

Start the Drain/Spin program. If the water drains normally, the problem was a temporary blockage. If the error remains, proceed to checking the pipe and pump. In machines with a system AquaStop (protection against leakage) before this step you need to reset the error by turning off the power for 1 minute.

Step 4. Pump diagnostics

To check the pump, unplug the machine, remove the bottom panel and disconnect the wires from the pump. Measure the winding resistance with a multimeter - normal value for Bosch 150–200 Ohm. If the device shows “1” (open) or “0” (short circuit), the pump must be replaced.

⚠️ Attention: In models Bosch Serie 8 with inverter motors the pump is integrated into the system EcoSilence Drive. Replacing it requires reflashing the control board - entrust this to a service center.

How to fix error E21 yourself

If diagnostics reveal a problem that can be solved without calling a technician, use these instructions. We have described the process for each case, taking into account the technical features Bosch.

1. Cleaning the filter and pump impeller

To do this you will need: a screwdriver (Phillips or flathead), pliers and a rag. Algorithm:

1. Disconnect the machine from the network and water.
2. Open the filter cover (lower right side of the front panel).
3. Place a water container and slowly unscrew the filter counterclockwise.
4. Remove debris from the filter and pump opening. Check if the impeller rotates (it should rotate with a light touch).
5. Rinse the filter under running water and install it back, tightening it until it stops.

2. Cleaning the drain pipe

This procedure is more complicated and requires partial disassembly of the machine. Be prepared to have to remove the front panel. Step by step:

• 🔧 Remove the bottom bar (usually attached to latches or 2-3 screws).
• 🔍 Find the pipe (corrugated tube between the tank and the pump) and loosen the clamps.
• 🧹 Remove debris from the pipe, rinse it with warm water. Check for cracks.
• 🔄 Reassemble everything in reverse order, making sure the clamps are tight.

3. Replacing the drain pump

If the pump is faulty, it must be replaced. For Bosch original pumps with article numbers are suitable 00642197 (for series 4/6) and 00642198 (for series 8). Replacement process:

1. Turn off the power and drain the water through the filter.
2. Remove the bottom panel and disconnect the wires from the pump.
3. Loosen the pipe clamps, remove the pump and install a new one.
4. Connect the wires and check the operation in test mode.

For models with system AquaStop After replacing the pump, you may need to reset the error through the service menu. To do this:

1. Turn on the machine.
2. Hold the "Start/Pause" and "Spin" buttons for 5 seconds.
3. In the service menu, select "Reset".

When you can't do without a master

There are situations when self-repair is not only ineffective, but also dangerous. Contact the service center if:

• 🔌 Error E21 accompanied by other codes (E16, E18, E23) - this indicates problems with the control board.
• 💻 After replacing the pump or cleaning the filter, the error remains, but the water still does not drain.
• ⚡ The machine “electric shocks” or emits a burning smell when working.
• 🔧 Replacement of pipes or seals is required in models with the system AquaStop (special equipment is needed to check for leaks).

The cost of repairs in the service depends on the problem:

• 🔧 Pump replacement: 2,500–4,000 ₽ (with spare parts).
• 📊 Diagnostics and flashing of the board: 1,500–3,000 ₽.
• 🔄 Replacement of the pressure switch: 1,800–3,500 ₽.
• 🛠 Complete cleaning of the drain system: 1,200–2,500 ₽.

For models Bosch Serie 8 with a warranty of up to 5 years (if registered on the manufacturer’s website), repairs can be free. Check the warranty status using the serial number of the machine on the official website Bosch.

⚠️ Attention: If the machine is under warranty, do not open the seals or carry out repairs yourself - this will void the warranty.

Preventing error E21

To avoid reappearance E21, follow these guidelines:

• 🧺 Use bags for washing delicate items (they prevent lint and threads from getting into the drain system).
• 🧼 Clean the pump filter once every 3 months, even if there are no errors.
• 🚿 Connect the machine to the water supply through a coarse filter.
• 📏 Watch the slope of the drain hose (lifting height is at least 60 cm).
• 🧹 Once every six months, run the “Drum Cleaning” program with citric acid (30 g at 60°C).

For models with SpeedPerfect (accelerated wash) the manufacturer recommends using liquid detergents - they form less deposits in the drain system. Also avoid overloading the drum: for machines Bosch with a load of 7 kg, the optimal weight of the laundry is 5–6 kg.

If your region has hard water, carry out preventive cleaning every 6 months using descaling agents (for example, Bosch TZ8001). This will prevent deposits from forming in the pipes and pump.

What should I do if error E21 appears after a power outage?

In this case, the surge protection was triggered. To reset the error:

1. Unplug the machine for 10 minutes.

2. Turn on and hold the "Start/Pause" button for 5 seconds.

3. Start the "Drain" program.

If the error remains, check the voltage stabilizer or surge protector - they may be faulty.

Frequently asked questions about error E21

Is it possible to continue washing if error E21 appears?

No, you cannot continue washing. Error E21 blocks the operation of the machine until the problem is resolved. Attempts to restart the program may lead to overheating of the pump or failure of the control board. First, drain the water manually (through a filter or emergency hose, if provided in the model), then proceed with diagnostics.

Error E21 appears only during a spin cycle. What's the matter?

If the problem manifests itself precisely at the spin stage, the most likely causes are:

• There is a blockage in the pipe between the tank and the pump (during the spin cycle, water enters the drain under high pressure and “clogs” the clearance).
• Malfunction of the water level sensor (pressostat) - the machine “does not understand” that the water has been drained.
• Problems with the tachometer (in direct drive models EcoSilence Drive), which regulates the spin speed.

Start by checking the pipe and pressure switch.

After cleaning the filter, error E21 disappeared, but returned a week later. Why?

This is a typical situation for machines connected to a water supply without a filter. Small particles (sand, rust) gradually accumulate in the drain system. Solution:

1. Install a coarse filter at the water supply inlet.
2. Wash the pipe between the tank and the pump (there may be debris left there).
3. Check the condition of the drain hose - sometimes a film of detergent forms inside, which narrows the clearance.

E21 flashes on the display, but the water drains normally. What does it mean?

In this case, the problem is most likely in the water level sensor (pressure switch) or the control board. The machine “thinks” that the water has not been drained, although in fact everything is in order. Try resetting the error by turning off the power for 5 minutes. If the code appears again, you will need to diagnose the pressure switch with a multimeter or replace the board.

How much does a pump for Bosch cost and where can I buy it?

The cost of the original pump for Bosch depends on the model:

• 00642197 (episodes 4/6) — 2,200–3,000 RUR.
• 00642198 (episode 8) — 3,500–4,500 RUR.
• Universal analogues (for example, Askoll) — 1 500–2 500 ₽.

It is better to buy spare parts from official service centers Bosch or trusted online stores (for example, 220-volt.ru, All-Zapchasti). Pay attention to the article number - it must match the original one. For models with system AquaStop Only pumps marked Aqua.