What 4 Means
A value of 4 in the service test programme of an older Bosch dishwasher is the water filling fault. It is the same family of problems the machine shows to the owner as a single letter on the display: not filling, overfilling, underfilling, or water collecting in the base. Because these numbers add together, a displayed 6 is this fault together with the heating fault.
Common Causes of 4
- Blocked inlet screen or a partly closed supply valve
- Inlet valve passing water or failing to open
- Float switch in the base triggered by collected water
🔧 One Safe Check You Can Try
Close the dishwasher's supply valve under the sink if there is any sign of water in the base, then check the inlet hose for a kink and rinse the filter screen inside the hose coupling at the tap end.
⚠ Why You Shouldn't Go Further Than That
- One of the possibilities behind this number is water in the base, which is a situation that gets worse every time the machine is restarted.
- The inlet valve is on the pressurised side of the supply, so removing it without closing the valve sprays water into the cabinet.
- Telling a real leak from a stuck float needs the machine drawn out, and a built-in unit is screwed to the counter.
- On machines of this age the original float and inlet valve have both had a long life, and either can be responsible.
Opening a panel to inspect or repair something yourself doesn't automatically cancel your manufacturer's warranty — but it can risk accidental damage, and some manufacturers do have specific service conditions. Check your product's warranty terms, or ask us, before deciding.