How to read/write DTCs using GM MDI GDS2

car diagnostic tool

Look here: GM GDS2 Diagnostics


To enter Diagnostics, select the Diagnostics icon (1) from the main application screen.


The Diagnostic Data Display application provides real-time status of the vehicle controller data and signals.

On the GDS2 Diagnostic Data Display, available data lists are available from a drop down menu.

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The slide below provides additional directional selections for graphical displays.

The Scroll Bar is found on the right of the graph and selection drop down menu.

It allows you to scroll up or down in the data lists.


DTC Display

When Diagnostic Trouble Codes (DTC)/DTC Display is selected, a summary screen with a set of columns including Control Module Name, Control Module Status, and DTC Count are displayed.


Refresh DTCs

If ‘Refresh’ is selected, GDS2 will request a DTC update from the controller


Details Selection

If ‘Details’ was selected, a detailed DTC display screen appears.


Control Module (1), DTC (2), Symptom Byte (3), Description (4), Symptom Description (5), and Status Byte (6) are all displayed at the top of the chart.

At the bottom of the chart Category (7) and Decoded Value (8) are shown.

Back (9) returns you to the DTC display.


Clear DTCs

If Clear DTCs (11) is selected, a DTC Display screen will appear


Use Add (1) or Add All (2) to select the ECUs you want to clear.

Some ECUs can only be cleared together, in which case they will be selected together. Select Remove (3) to start the process to clear the selected ECUs.

Select Remove All (4) to start the process to clear all the ECUs.

Select OK (5) to clear selected ECUs.

Select Cancel (6) if you do not want to clear any ECUs at the current time.

If OK is selected, a message to clear DTCs will appear.

The deleted codes will disappear with the next refresh.

Leave the DTC Application


Note: Only the Close Application (6) selection allows you to completely leave the Diagnostic Application.

It is not possible to exit GDS2 while diagnostic applications are being performed.

To Exit GDS2, navigate back to the GDS2 Application page by selecting the Back (7) followed by Home (9) when it is available.

Link to GDS2: