Chart A-2 No Serial Data

Chart A-2 No Serial Data (Part 1 Of 2):

Chart A-2 No Serial Data (Part 2 Of 2):

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

CIRCUIT DESCRIPTION
There should always be a steady Malfunction Indicator Lamp (MIL) (Service Engine Soon) when the ignition is "ON" and engine is "OFF." Battery voltage is supplied to the light bulb. The Vehicle Control Module-A (VCM-A) will turn the light "ON" by grounding CKT 419. (If MIL is not illuminated, use Chart A-1.) Related Tests, Information and Procedures

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. If there is a problem with the VCM-A that causes a Tech 1 scan tool to not read serial data, the Tech 1 should not be able to command the MIL. Be sure that the scan tool is working properly on another vehicle. If the scan tool is functioning properly and CKT 1807 is OK, the VCM-A may be at fault for the NO Data Link Connector (DLC) symptom.
2. This test checks the ability of the VCM-A to control the MIL. The Tech 1 has the ability to command the MIL "ON" and "OFF."
3. Checks for B+ to terminal "16" of the DLC. This is used to power the Vehicle Interface Module (VIM).
4. Checks for a ground at terminal "4" of the DLC. This is used to ground the VIM.
5. Checks for proper operation of the cigar lighter. The Tech 1 is power through the cigar lighter.
6. This step verifies proper operation of the scan tool.
7. When serial data is operating properly, the voltage should vary from 1 to 7 volts. This step checks the integrity of the serial data line.
8. This step checks for a short to ground in CKT 1807.
9. This step checks for a short to ground, or open in CKT 1807, VCM-A connections, or faulty VCM-A.
10. This step checks for a short to voltage in CKT 1907, or a faulty VCM-A.

DIAGNOSTIC AIDS
Check DLC for poor connection check Tech 1 connector.
^ If VCM-A has not been programmed (service replacement) it will not display data for powertrain controls.