Auxiliary enzyme of beta-oxidation. Participates in the degradation of unsaturated fatty enoyl-CoA esters having double bonds in both even- and odd-numbered positions in peroxisome. Catalyzes the NADP-dependent reduction of 2,4-dienoyl-CoA to yield trans-3-enoyl-CoA. Has activity towards short and medium chain 2,4-dienoyl-CoAs, but also towards 2,4,7,10,13,16,19-docosaheptaenoyl-CoA, suggesting that it does not constitute a rate limiting step in the peroxisomal degradation of docosahexaenoic acid. a (2E,4Z)-dienoyl-CoA + H(+) + NADPH = a 4,5-saturated-(3E)-enoyl-CoA + NADP(+) a (2E,4E)-dienoyl-CoA + H(+) + NADPH = a 4,5-saturated-(3E)-enoyl-CoA + NADP(+) (2E,4Z,7Z,10Z,13Z,16Z,19Z)-docosaheptaenoyl-CoA + H(+) + NADPH = (3E,7Z,10Z,13Z,16Z,19Z)-docosahexaenoyl-CoA + NADP(+) Monomer, dimer and oligomer. Belongs to the short-chain dehydrogenases/reductases (SDR) family. 2,4-dienoyl-CoA reductase subfamily.