Without Scan Tool

The provision for communicating with the Engine Control Module (ECM) is the Data Link Connector (DLC). The DLC is located behind the left "A" Pillar Panel. It is used in the assembly plant to receive information in checking that the Engine is operating properly before it leaves the plant. The Diagnostic Trouble Code(s) (DTCs) stored in the ECM's memory can be read by counting the number of flashes of the Malfunction Indicator Lamp (MIL) when the Diagnostic Test Terminal of the DLC is grounded. The DLC Terminal "1" (diagnostic request) is pulled "Low" (grounded) by jumping to DLC Terminal "3", which is a Ground Wire. This will signal the ECM that you want to "flash" DTC(s), if any are present.

Once Terminals "1" and "3" have been connected, the Ignition Switch must be moved to the "ON" position, with the Engine not running. At this point, the MIL should flash DTC 12 three times consecutively. This would be the following flash, sequence: "flash, pause, flash-flash, long pause, flash, pause, flash-flash, long pause, flash, pause, flash-flash". DTC 12 indicates that the ECM's diagnostic system is operating. If DTC 12 is not indicated, a problem 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 a DTC three times if a DTC is present, or it will simply continue to output DTC 12. If more than one DTC has been stored in the ECM's memory, the DTC(s) will be output from the lowest to the highest, with each DTC being displayed three times.