Error code reference

Bosch Dishwasher Error Code 4

Unexpected heating detected (heating is taking place at a stage of the program where it should not).

Bosch codesBosch dishwasher codes

Unexpected heating detected (heating is taking place at a stage of the program where it should not).

First step from the service manual

Detected after 60 seconds; results in program aborted FATAL ERROR.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What 4 means on a Bosch dishwasher

Error code 4 on a Bosch dishwasher indicates a water filling fault. The control board monitors how long the dishwasher takes to reach the required water level during the fill phase. When the inlet valve opens but the pressure sensor or flow meter does not detect sufficient water entering the tub within the expected timeframe, the board triggers E4 and halts the cycle. This fault is directly tied to the water supply path: inlet valve, water supply line, inlet hose, and the pressure switch or aqua sensor that confirms fill completion.

For homeowners, this error means your dishwasher started a cycle but could not pull in enough water to proceed. The machine detected that the tub was not filling correctly and stopped to prevent running dry, which could damage the pump and heating element. In most cases, the fix is found somewhere between the water supply valve on the wall and the inlet valve assembly inside the door.

Common triggers include a closed or restricted water supply valve, a kinked or clogged inlet hose, a failed water inlet valve that is not opening properly, or a faulty pressure switch that is not correctly reporting the water level to the control board.

Source: manufacturer service documentation.

Common causes of 4

  1. 01

    Closed or restricted household water supply valve

    Wiring / connection

    If the shutoff valve under the sink or behind the dishwasher is partially or fully closed, the dishwasher cannot draw sufficient water during the fill phase. This is the first physical item to check before pursuing any part replacement.

  2. 02

    Kinked or clogged inlet hose

    Wiring / connection

    The inlet hose connecting the household supply to the dishwasher inlet valve can become kinked during installation or use, or accumulate mineral deposits over time that restrict flow enough to trigger the fill fault.

  3. 03

    Failed water inlet valve

    Part replacement

    The water inlet valve is a solenoid-operated valve that opens to allow water into the tub. If the solenoid coil fails, the valve screen becomes blocked with debris, or the valve body cracks, it will not open or flow at the required rate, preventing proper fill.

  4. 04

    Faulty water pressure switch or flow meter

    Part replacement

    The pressure switch or flow meter tells the control board when the tub has reached the correct water level. If this component fails or loses its connection to the control board, the board never receives confirmation that filling has completed, triggering E4 even when water is physically entering the tub.

See the test procedure for each cause

Frequently asked questions about 4

What does error code 4 mean on a Bosch dishwasher?
Error code 4 on a Bosch dishwasher signals a water filling fault. The control board opened the inlet valve but did not detect that the tub filled to the required level within the expected time. The problem typically originates in the water supply path, including the household shutoff valve, inlet hose, or the inlet valve itself.
How do I fix error code 4 on a Bosch dishwasher?
Start by checking that the household water supply valve is fully open and that the inlet hose has no kinks or visible blockages. If water supply is confirmed good, remove the inlet hose and inspect the inlet valve screen for mineral buildup or debris, cleaning it if clogged. If those steps do not clear the fault, test or replace the water inlet valve, and if the valve tests functional, inspect the pressure switch and its hose for blockages or cracks.
Can I still use my Bosch dishwasher when error code 4 is showing?
You should not continue running the dishwasher with E4 active. The machine halted the cycle because it could not confirm adequate water in the tub. Running a wash or drain cycle without proper water fill risks damaging the circulation pump and heating element, both of which require water for lubrication and cooling. Resolve the fill fault before running another cycle.
How much does it cost to fix error code 4 on a Bosch dishwasher?
If the fix is simply opening a closed shutoff valve or straightening a kinked hose, the cost is zero. A replacement water inlet valve for a Bosch dishwasher typically costs between 25 and 60 dollars in parts, and is a moderate DIY repair requiring disconnection of the water supply and removal of the door panel. A pressure switch runs roughly 20 to 50 dollars. If hiring a technician, expect a diagnostic fee plus one hour of labor, bringing total repair costs to roughly 150 to 250 dollars depending on region and the part needed.
Is error code 4 on a Bosch dishwasher a serious problem?
E4 is a protective fault, not a catastrophic failure. In many cases it has a simple cause like a closed valve or kinked hose that costs nothing to fix. Even if the inlet valve needs replacement, it is a relatively accessible repair. The code becomes more costly only if the fault was ignored and the pump or heating element sustained damage from running dry, which is why the machine stops and displays the code rather than continuing.

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