Yields of electroweak gauge bosons can be used to probe the nuclear parton distribution functions of quarks and antiquarks. Final results on W boson production in pPb collisions at a nucleon-nucleon center-of-mass energy of 8.16 TeV using the CMS detector will be presented. The muon decay channel is used to study both positive and negative W bosons as a function of muon pseudorapidity. Rapidity and charge asymmetries in the W yield are studied. Comparisons to theory calculations show that these data are sensitive to the presence of nuclear modifications to the parton distributions in the lead nucleus, and can help improve and constrain theoretical calculations.