Acts as a co-chaperone with Hsp70 required to promote protein folding and trafficking, prevent aggregation of client proteins, and promote unfolded proteins to endoplasmic reticulum-associated degradation (ERAD) pathway (By similarity). Acts by determining Hsp70's ATPase and polypeptide-binding activities (By similarity). Can also act as a chaperone that promotes maturation of potassium channel unc-103 by stabilizing nascent channel subunits and assembling them into tetramers (PubMed:27916661). Expressed in many head neurons, vulva muscles and some tail neurons. Belongs to the DnaJ family. DNAJB12/DNAJB14 subfamily.