A dishwasher needs both supply pressure and permission from its safety controls.
Start Here
Confirm under-sink valve is open.
Inspect supply hose.
Check float movement where accessible.
Clean inlet filter only if manufacturer allows.
Listen for inlet-valve sound.
The fastest way to get lost is to remove parts before you know which function failed. A dishwasher needs both supply pressure and permission from its safety controls. For dishwasher does not fill, concentrate on fill, circulation, filtration and drain flow. Use every working function as evidence: if one stage still behaves normally, that fact eliminates causes that would have stopped the appliance earlier in the sequence.
Observe the timing before touching anything. Note what happens immediately after Start, what changes just before the fault, and what remains normal afterward. Lights, relay clicks, water movement, motor or fan sounds, heat, vibration and error codes are useful only when tied to a point in the cycle. A fault that appears instantly is a different problem from one that appears only after the machine warms up or reaches a later stage.
Begin with the cheapest conditions to verify: confirm under-sink valve is open, then inspect supply hose. Do not merely glance at them. Compare the actual condition with the manual, correct anything obviously wrong, and retest before moving deeper. Simple installation, maintenance and user-setting problems regularly imitate failed electrical parts.
If those checks pass, move to check float movement where accessible. Then decide whether clean inlet filter only if manufacturer allows can be evaluated safely with power isolated. Choose one test that answers one question: blocked or clear, open or closed, free or jammed, intact or electrically open. If a test result would not change your next decision, the test is probably not worth doing.
Avoid bypassing the float switch, loosening pressurized fittings while energized, and assuming the pump controls filling. All three skip evidence and can turn a minor fault into an expensive one. After a correction, reassemble guards and connectors, restore normal settings, and reproduce the original operating conditions. A single successful start is not proof; the original symptom must stay gone through the stage that used to fail.
A Safe Step-by-Step Check
Document the exact symptom and pay special attention to confirm under-sink valve is open.
Remove external causes first; specifically verify inspect supply hose.
With power isolated where required, inspect check float movement where accessible and then evaluate clean inlet filter only if manufacturer allows only if it can be done safely.
Reassemble fully and run a controlled test under the conditions that previously caused the fault.
Common Beginner Mistakes
Bypassing the float switch.
Loosening pressurized fittings while energized.
Assuming the pump controls filling.
STOP AND GET HELP: If the next useful test requires exposed live mains, defeating a safety interlock, opening a sealed refrigeration circuit, disturbing gas controls, or entering a microwave high-voltage section, the diagnosis has reached the professional-service boundary.