Without Scan Tool

ALDL Connector Terminal Identification.:

Due to software changes and the removal of the diagnostic enable circuit (by using 16 pin DLC), Diagnostic Trouble Codes (DTCs) may no longer be obtained by grounding "A" to "H" at the Data Link Connector (DLC). The use of a Tech 1 scan tool or equivalent will be needed to obtain both current and history DTCs. If the vehicle has a 12 pin DLC that contains a pin "A" and "H" then flashing codes MAY be possible by following this procedure.

Ground terminal "H" to terminal "A" of the DLC, Fig. 14, and counting the Anti-Lock lamp flashes. The terminals must be jumped for a few seconds before the diagnostic trouble codes will begin to flash.