GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The DLC provides battery positive voltage for the scan tool at terminal 16 and battery negative voltage at terminal 4. The DLC provides the class 2 serial data signal at terminal 2 and signal ground at terminal 5. The scan tool will power up with the ignition OFF.

Test Description

Step numbers below refer to the same step numbers in the Diagnostic Table

  1. The AUX POWER fuse supplies power to the DLC terminal 16.

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

Step

Action

Yes

No

Schematic Reference: Data Link Connector Schematics

1

Test the DLC battery positive voltage circuit 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 Systems for the applicable Diagnostic System Check

Go to Step 2

2

Test the DLC battery negative voltage circuit 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 Systems for the applicable Diagnostic System Check

Go to Step 3

3

Inspect for poor connections at the DLC terminals 4 and 16. 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 Systems for the applicable Diagnostic System Check

Go to Step 4

4

The scan tool may be malfunctioning. Refer to the scan tool instruction manual.

Did you obtain a properly operating scan tool?

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

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