GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The data link connector (DLC) provides operating power for the scan tool at terminal 16 for battery positive voltage, and at terminal 4 for ground. The scan tool will power up with the ignition off. The DLC provides the signal ground at terminal 5, class 2 serial data signal at terminal 2, UART serial data signal at terminal 9 and E and C serial data signal at terminal 14.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. The CIG LTR fuse supplies power to terminal 16 of the DLC.

  2. The battery positive voltage and ground circuits of the DLC are functioning properly. The malfunction must be due to the scan tool.

Step

Action

Yes

No

1

Test the battery positive voltage circuit of the DLC for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Control Module References in Body Control System for the applicable Diagnostic System Check

Go to Step 2

2

Test the ground circuit at terminal 4 of the DLC for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Control Module References in Body Control System for the applicable Diagnostic System Check

Go to Step 3

3

Inspect for poor connections at terminals 4 and 16 of the DLC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Control Module References in Body Control System for the applicable Diagnostic System Check

Go to Step 4

4

The scan tool may be malfunctioning. Refer to the scan tool user guide.

Did you obtain a properly operating scan tool?

Go to Control Module References in Body Control System for the applicable Diagnostic System Check

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