Chart A-2 No Serial Data

Chart A-2 No Serial Data:

No MIL (Service Engine Soon) & No Serial Data:

CIRCUIT DESCRIPTION
There should always be a steady Malfunction Indicator Lamp (MIL) when the ignition is "ON" and engine stopped. Battery voltage is supplied to the light bulb. The Vehicle Control Module (VCM) will turn the light "ON" by grounding CKT 419 at the VCM.

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test confirms that the VCM can communicates with the Tech 1.
2. There should be 4-5 volts present.
3. If voltage remains at the Data Link Connector (DLC) when the VCM connector is disconnected, then CKT 800 is shorted to voltage.
4. This step will check for an open serial data CKT 800.
5. At this point the wiring is OK. The problem is a faulty VCM connection or VCM.

DIAGNOSTIC AIDS
Check DLC for poor connection check Tech 1 connector.