As part of the MCIA complex, involved in the assembly of the mitochondrial complex I. Part of the mitochondrial complex I assembly/MCIA complex that comprises at least the core subunits TMEM126B, NDUFAF1, ECSIT and ACAD9 and complement subunits such as COA1 and TMEM186. Interacts with ECSIT. Interacts with ACAD9. At early stages of complex I assembly, it is found in intermediate subcomplexes that contain different subunits including NDUFB6, NDUFA6, NDUFA9, NDUFS3, NDUFS7, ND1, ND2 and ND3. Interacts with TMEM70 and TMEM242 (By similarity). Periferally associated with the matrix face of the mitochondrial inner membrane. Belongs to the CIA30 family.