As part of the MCIA complex, required for efficient 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 (PubMed:32320651). Interacts with MT-ND3 (PubMed:32320651). Belongs to the TMEM186 family.