Data Link Connector: Description and Operation

ALDL Connector:

PURPOSE
The Data Link Connector (DLC) provides a means of communicating with the ECM concerning engine and transmission operating parameters and accessing Diagnostic Trouble Codes (DTC).

OPERATION
The ECM communicates a variety of information through the Serial Data Line (DLC terminal "M"). The data is transmitted at a high frequency which requires a Tech 1 diagnostic computer (scan) tool for interpretation. There are several other non-OEM scan tools available for displaying the same information.

CAUTION: A Scan tool that displays faulty data should not be used and the problem should be reported to the manufacture. The use of a faulty scan tool can result in misdiagnosis and unnecessary parts replacement.

DTC's can also be accessed without a scan tool by grounding terminal "B" with the engine not running and the ignition switch in the "ON" position. The Malfunction Indicator Lamp (MIL) "SERVICE ENGINE SOON" light will flash a Code 12 three times and then flash each code stored in memory three times. Once all Codes are retrieved, a Code 12 will follow. New codes cannot be stored in the ECM once the diagnostics mode is activated.

LOCATION
The Data Link Connector is located in the passenger compartment.