You'll have to break down and buy a new sensor, that's likely the issue. If your cell is over 4 or 5 years old, it may make sense to buy the cell and sensor combo, as they have discontinued the 1400 older design. Our old cell just crapped out after 4 years. 4-5 is the life cycle. The new design has to be replumbed, but if you are handy, it's easy PVC plumbing....About $800 for the replacement cell /sensor on the internet...

Yes, shock the pool, and get some algae control in there. We use a bag or 2 of shock every once in a while after the pool gets a heavy kid use. You are going to need to shock the water to get the chlorine level up anyway before you re-start the salt system to give it a jump start.

that is coincidental. My Aquapure 1400 just did the same thing. I am getting error 172/186. This will be the 3rd time in 3 years that it has died on me. Last time was the same error. Time before was the board.

This is getting tiring.
Chris