Acts as a co-chaperone with HSPA8/Hsc70; required to promote protein folding and trafficking, prevent aggregation of client proteins, and promote unfolded proteins to endoplasmic reticulum-associated degradation (ERAD) pathway. Acts by determining hspa8/Hsc70's ATPase and polypeptide-binding activities. Can also act independently of hspa8/Hsc70: together with dnajb12, acts as a chaperone that promotes maturation of potassium channels by stabilizing nascent channel subunits and assembling them into tetramers. While stabilization of nascent channel proteins is dependent on hspa8/Hsc70, the process of oligomerization of channel subunits is independent of hspa8/Hsc70. Belongs to the DnaJ family. DNAJB12/DNAJB14 subfamily.