Diagnostic Mode Description

Duty Check Datalink Connector:

DIAGNOSTIC MODE
When the diagnostic request terminal, located in the Duty Check Data Link Connector (DLC), is grounded with the ignition switch in the "ON" position (engine not running), the system enters what is called the diagnostic mode. In this mode, the Engine Control Module (ECM) will perform the following functions:
1. Display Diagnostic Trouble Code (DTC) 12 by flashing the Malfunction Indicator Lamp (MIL) (indicating the system is operating correctly).
2. Display any stored DTCs by flashing the MIL. If DTCs other than DTC 12 are stored, DTC 12 will not be flashed.
3. Output idle speed control duty through the duty check terminal of the Duty Check DLC.