An augmented reality (AR) system for diagnosis, troubleshooting and repair of industrial robots. The disclosed diagnosis guide system communicates with a controller of an industrial robot and collects data from the robot controller, including a trouble code identifying a problem with the robot. The system then identifies an appropriate diagnosis decision tree based on the collected data, and provides an interactive step-by-step troubleshooting guide to a user on an AR-capable mobile device, including augmented reality for depicting actions to be taken during testing and component replacement. The system includes data collector, tree generator and guide generator modules, and builds the decision tree and the diagnosis guide using a stored library of diagnosis trees, decisions and diagnosis steps, along with the associated AR data.