Taylor, 27, retired with a heart condition in April 2016 after seven England Tests and 27 one-day games.
He has since worked with Nottinghamshire and Yorkshire's academies in addition to media work.
"It's great to see his desire to still be involved with the game," head coach David Ripley said of Taylor's arrival.
"James has a fantastic 50-over record, averaging over 50 which is obviously outstanding.
"I believe he can offer good advice and relay his one-day cricket experiences on to our batsmen."
Meanwhile, former Northants captain Sales, who scored in excess of 22,000 runs in more than 20 years at the County Ground before his retirement in 2014, will work with the county's batsmen.
"David has been working part time with the batters since January, focusing on improving more of the technical aspects of their game," Ripley added.
"I believe his cricket brain and experience are a real positive for the squad and will go a long way to improving their overall game."
Former England batsman James Taylor has joined Northamptonshire as a coaching consultant, while David Sales has taken a part-time coaching role.