E4 appears when trying to use pressure cooking modes; the cooker does not build pressure.

Safety first: Ensure the cooker is fully depressurized before opening the lid. Unplug before cleaning internal parts.

• Check steam release position: Confirm the steam release knob or valve is set to Sealing, not Venting, for pressure programs.
• Inspect lid gasket: Remove the silicone sealing ring from the lid. Check for cracks, hardening, or deformation. Clean it with warm soapy water, rinse, dry, and reinstall firmly in its groove.
• Clean pressure sensor port: On many ProCook models, a small channel from the lid or lid frame leads to the pressure sensor. Use a thin brush or toothpick to gently clear any food residue from the port (do not push debris further in).
• Test with water only: Add 2–3 cups of water, close the lid, set to a short pressure program, and observe. If E4 persists and no pressure builds, the pressure sensor or its tubing may be defective and should be replaced.