A.O. Smith Water Heater Error Code 16

Error code 16 means the upper control board is detecting no current flowing through the power anode circuit, a condition called P-ANODE OPEN. This tells the control that the powered sacrificial anode rod is not functioning electrically. The fault is most often caused by a loose connector or a damaged wire between the power anode and the upper control board.

A simple reset will not permanently clear error code 16 because the control board will re-detect the open circuit in the power anode as soon as it checks the circuit again. The underlying wiring fault or component failure must be repaired before the code will stay cleared. Resetting can be useful to confirm the repair was successful after the fix is made.

If the fix is simply reseating a loose connector, there may be no parts cost at all, just labor time. Replacing a damaged wire or connector typically falls in the range of $50 to $150 in parts and labor depending on the extent of the damage. A failed power anode rod replacement or a control board replacement will cost more, generally ranging from $150 to $400 or higher depending on parts pricing and local labor rates.

Start by inspecting the wire that runs from the power anode to the upper control board for any visible damage, and check that all connectors are fully and firmly seated. If the wiring looks intact, test the power anode itself for continuity to determine whether it has failed internally. Replace any damaged wiring, connectors, or the anode rod as needed based on your findings.

The water heater may continue to heat water with code 16 active, but the power anode is not providing corrosion protection to the tank interior while this fault is present. Running the unit without active anode protection for an extended period can accelerate tank corrosion and shorten the life of the water heater. It is best to diagnose and repair the fault as soon as possible.