Without Scan Tool

Data Link Connector And Junction Block:

Duty Check DLC:

READING CODES WITHOUT SCAN TOOL
The provisions for communicating with the Electronic Control Module (ECM) are the Assembly Line Diagnostic Link (ALDL) connector, the "DIAG SW" connector in the junction block and the "DIAGNOSTIC REQUEST" terminal in the duty check coupler. The junction block is located under the instrument panel to the left of the steering column. The duty check coupler is located in the left rear engine compartment near the strut tower. Codes stored in ECM memory can be read by counting the flashes of the "CHECK ENGINE" indicator (or a test light) after grounding either the "DIAG SW" connector in the junction block or the "DIAGNOSTIC REQUEST" terminal in the duty check coupler. When either terminal is grounded, the ECM enters its diagnostic mode and outputs codes to either the "CHECK ENGINE" indicator or, if a test light is used, to the diagnostic output terminal of the duty check coupler.

To ground the "DIAG SW" connector in the junction block, simply remove the spare fuse from the junction block and insert it into the DIAG SW connector. Then, turn the ignition switch to "ON" and observe the "CHECK ENGINE" indicator.

To ground the diagnostic request terminal in the duty check coupler, connect a jumper between duty check coupler cavities "2" and "4". At this point, the "CHECK ENGINE" indicator should flash Code 12 continuously.
This would be the following flash sequence: "flash, pause, flash-flash, long pause, flash, pause, flash-flash, long pause, flash, pause, flash-flash," etc. Code 12 indicates that the ECM's diagnostic system is operating. If Code 12 is not indicated, a problem is present within the diagnostic system itself.