If a diode check reading shows OL on both sides, what does this indicate?

When a diode check reading shows an open loop (OL) indication on both sides, it signifies that the diode is open. In a healthy diode, current should flow in one direction when forward-biased, and there should be a measurable voltage drop. Conversely, if the diode is open, it will not conduct electricity at all in either direction, leading to an OL reading on both the forward and reverse bias tests.

This scenario clearly highlights a failure in the diode, as it should typically show low resistance (a forward voltage drop of approximately 0.6-0.7 volts for silicon diodes) when tested in one direction and a high resistance (or OL) in the reverse direction if functional. Therefore, an OL reading on both sides indicates that the diode is no longer providing the necessary conductive pathway, confirming its open status.