For 1990-2009 cars

### Circuit Description

The data link connector (DLC) provides operating power for the scan tool at terminal 16 (battery positive voltage) and at terminal 4 (ground). 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

1. The HZD 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 short to ground. Refer to Testing for Continuity and Testing for Short to Ground in Wiring Systems. Did you find and correct the condition? | Go to applicable Diagnostic System Check | Go to Step 2
2 | Test the ground circuit at terminal 4 of the DLC for an open. Refer to Testing for Continuity in Wiring Systems. Did you find and correct the condition? | Go to 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 in Wiring Systems. Did you find and correct the condition? | Go to 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 applicable Diagnostic System Check | --