Sometimes ICO can provide an incorrect display of the pH. It indicates that the pH is 17 or higher. This may be due to an error in the contact stage with the ICO’s circuit board.
To resolve this, follow these instructions (see here for pictures of the following instructions: https://ondilo.com/en/assistance/ico-support-sensors/how-to-resolve-the-problem-of-a-ph-that-is-too-high-ph-17/
Step 1: Remove ICO from the water and dry it properly
Step 2: Open the cover
Step 3: Hold down the button. The light flashes yellow once. ICO is turned off.
Step 4 : Remove the pH sensor (blue) from its place
Step 5 : Use a small, fine knife to push one or two strips away from the sensor to achieve some separation, as shown in the figure (see here).
Step 6: Reseat the pH sensor
Step 7: Hold down the button. The light flashes green three times. ICO is switched on.
Step 8: Put the cover back on
Step 9: Put ICO back in the water
Step 10 : Observe the next recorded pH values