Without Scan Tool

ALDL Connector (Located Underdash):

OBD Circuit:

DESCRIPTION
The means of communicating with the control module is the Data Link Connector (DLC) located under the instrument panel and is sometimes covered by a plastic cover labeled "DIAGNOSTIC CONNECTOR". Also, The DLC is used in the assembly plant to receive engine information to determine proper operation before it leaves the plant.
The Diagnostic Trouble Codes (DTC's) stored in the control module memory can be displayed by counting the number of flashes of the Malfunction Indicator Lamp (MIL) (Service Engine Soon) when the diagnostic terminal of the DLC is grounded.

OPERATION
The DLC terminal "B" (diagnostic terminal) is the second terminal from the right of the DLC top row. The terminal is most easily grounded by connecting it to terminal "A" (internal control module ground), which is located to the right of terminal "B" on the top row of the DLC.
When terminals "A" and "B" have been connected, the ignition switch must be turned to the "ON" position with the engine NOT operating.
The MIL (Service Engine Soon) should flash DTC 12 three times consecutively. This would be the following flash sequence: One flash, pause, two flashes, long pause, one flash, pause, two flashes, long pause, one flash, pause, two flashes. DTC 12 indicates that the control module diagnostic system is operating properly. If DTC 12 is NOT indicated, a fault is present within the diagnostic system itself, and should be addressed by consulting the appropriate diagnostic chart.
Following the output of DTC 12, the MIL will indicate any DTC three times consecutively. However if no other codes are present will continue to repeat DTC 12. If more than one diagnostic trouble code has been stored in the control module memory, the DTC's will be displayed from the lowest to the highest with each DTC being displayed three times.

In this mode the control module will:
- Display a DTC 12 by flashing the Malfunction Indicator Lamp (MIL) "SERVICE ENGINE SOON". This indicates the system is operating properly.
- Display any DTC(s) by flashing the Malfunction Indicator Lamp (MIL) "SERVICE ENGINE SOON". Each DTC will be flashed three times then DTC 12 will be flashed again. New codes cannot be stored in the control module once the diagnostics mode is activated.
- Energize all control module cotrolled relays and solenoids except the fuel pump relay. This allows checking circuits which may be difficult to energize without driving the vehicle and being under particular operating conditions.
- The IAC valve moves to its fully extended position, on most models blocking the idle air passage. This is useful in checking the minimum idle speed.