Without Scan Tool

Entering the self-diagnostic function

Before doing the self-diagnostic function, check the No. 5 (7.5 A) fuse, the No. 21 (10 A) fuse and the No. 32 (10 A) fuse in the driver's under-dash fuse/relay box.
1. Turn the ignition switch OFF.
2. Press and hold the call answer/call end (white phone) button, and turn the ignition switch from off (0) to ACC (I) three times within 6 seconds ending with the ignition switch in ACC (I).







3. The indicator will flash (green or red) if any failures have been detected. Troubleshoot the DTCs as indicated below.

NOTE:
- When the OnStar system enters the self-diagnostic mode, if the OnStar system has current DTCs, OnStar system will flash the red LED to display current DTCs.
- If the OnStar system has only history DTCs, then the OnStar system will flash the green LED to display history DTCs.
- When the ignition switch is turned OFF after 3 seconds of DTC display, the OnStar system will exit the self-diagnosis mode and turn OFF.
- When there is no operation after DTC display, then OnStar system will exit self-diagnosis mode.