Safety first: Unplug the dishwasher and close the water tap. Expect water in the base.

Step-by-step checks:

Remove water from base: Pull the dishwasher out and tilt it slightly backward to access the base tray. Use towels or a sponge to remove all water. This may temporarily clear E15 but does not fix the leak.
Inspect components for leaks: With side panels removed, run a short fill cycle while observing. Pay attention to the circulation pump seal, heater housing joints, inlet valve, and all hoses.
Tighten or replace clamps: If a hose connection is weeping, tighten the clamp or replace it with a new stainless-steel clamp.
Replace faulty parts: If the circulation pump shaft seal is leaking or the sump gasket is cracked, replace the affected assembly with a Vestel-compatible part.
Float switch: Verify that the anti-flood float and microswitch move freely and are not stuck in the activated position.

After repair, ensure the base is completely dry and run a full cycle while monitoring for any new leaks.

Dishwasher displays E15 and may run the drain pump continuously; water is often found in the base tray.

Possible Causes