Reading DTCS
- Perform on-board diagnostic system check before diagnosing vehicle using self-diagnostic system. See appropriate ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK chart under DIAGNOSTIC DTC CHARTS.
- DTCs can be retrieved using a scan tool connected to Data Link Connector (DLC) or by counting flashes of Malfunction Indicator Light (MIL) after grounding either DIAG SW connector in fuse block or diagnostic request terminal in duty check data link connector, located on left side of firewall. See Fig 1
.
- To retrieve DTCs using DIAG SW connector in fuse block, remove spare fuse from fuse block and insert into DIAG SW connector terminal. See Fig 1
. Turn ignition on and observe MIL to read DTCs. Proceed to appropriate charts under DIAGNOSTIC DTC CHARTS to diagnose DTCs.
- To retrieve DTCs using the duty check data link connector, connect jumper wire between duty check data link connector terminals No. 2 and 4. See Fig 1
. Turn ignition on and observe MIL to read DTCs. If DTCs are stored, DTC will flash 3 times, starting with the lowest DTC. Proceed to appropriate charts under DIAGNOSTIC DTC CHARTS to diagnose DTCs.
- If no DTCs are stored, MIL will flash DTC 12, indicating ECM diagnostic system is operating.
Courtesy of GENERAL MOTORS CORP.