Chimbote (5493m) has been climbed. It was widely considered the highest unclimbed mountain in the Andes, and certainly the highest unclimbed 'real' mountain. ie. ignoring minor sub-peaks of higher mountains and mounds in the Atacama.

North of Tupungato, south of the road south of Aconcagua, it has been attempted more than a few times over the last 20 years and most came back reporting terrible rock as one of the main reasons for failure.

Full report, in Spanish: http://desnivel.com/alpinismo/fainberg- ... l-chimbote