This part is a kind of semiconductor called 5031SM.

Function of this product has Zener Diode.

Manufacturers : NTE Electronics

Image and pinout :

Some of the text within the PDF file :

NTE5005SM thru NTE5031SM Zener Diode, 300mW ±5% Tolerance Features: D Zener Voltage 3.3V to 24V D SOT–23 Type Surface Mount Package Absolute Maximum Ratings: Maximim Repetitive Peak Forward Current, IFRM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250mA Maximim Repetitive Peak Working Current, IZRM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250mA Forward Voltage (IF = 10mA, TJ = +25°C), VF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 900mV Total Power Dissipation (TA ≤ +25°C, Note 1), Ptot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350mW Maximum Junction Temperature, TJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +175 [ ... ]

5031SM PDF Datasheet Download