Gretio, developed by Surreal Development LLC, is a free iOS application designed for vehicle diagnostics, specifically tailored for General Motors vehicles. By utilizing Gretio with an OBDLINK MX+, users can access advanced diagnostic functions effortlessly. The app allows users to analyze a vast array of data points rapidly, providing detailed insights into various vehicle modules such as the Engine Control Module, Chassis Control Module, and more.

With Gretio, users can easily look up diagnostic trouble codes for different modules and perform advanced service functions like diesel particulate filter service regenerations and selective catalytic reduction tests. This tool is particularly aimed at the DIY market, emphasizing the importance of following the vehicle's service manual or other OEM approved literature for all procedures.