GM Service Manual Online
For 1990-2009 cars only

Flash DTC Diagnostics

Flash DTC diagnostics read current DTCs. You can enable FLASH DTC diagnostics by locating the Data Link Connector (DLC) which is in the LH rear of the engine compartment, mounted to the strut tower. Connect a jumper between terminal (Tc) and terminal (E1) with the ignition ON, and the engine OFF. This action pulls the cruise control module (CCM) terminal 5 to ground and signals the CCM to enter the FLASH DTC diagnostic display mode.

The CCM displays the DTCs by flashing the cruise control indicator lamp. Each DTC that is displayed consists of the following:

    • A series of flashes which represent the tens (first) DTC digit
    • A 2.5 second pause
    • A series of flashes which represent the ones (second) DTC digit

For example, a FLASH DTC of 32 would be displayed as: three flashes, a 2.5 second pause, and two more flashes. Each DTC is flashed once before moving on to the next DTC. After all the DTCs are displayed, the entire DTC sequence is continually repeated until you remove the jumper from the DLC.

If there are no DTCs present, the CCM will flash the CRUISE indicator lamp continuously. This indicates that FLASH DTC diagnostics have been enabled. The SDM will continue to flash the Cruise indicator lamp until the jumper wire is removed from the DLC.