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 UART serial data signal at terminal 9 and signal ground at terminal 5. The DLC also provides the class 2 serial data signal at terminal 2 and signal ground at terminal 5. The DLC also provides the E+C serial data signal at terminal 14 and signal ground at terminal 5. The scan tool will power up with the ignition off.

### Test Description

1. The CIGAR/DLC 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
--- | --- | --- | ---
1 | Test the DLC battery positive voltage circuit for an open or a short to ground. Refer to Flat Wire Repairs in Wiring Systems. Did you find and correct the condition? | Go to the applicable Diagnostic System Check | Go to Step 2
2 | Test the DLC ground circuit terminal 4 for an open. Refer to Flat Wire Repairs in Wiring Systems. Did you find and correct the condition? | Go to the applicable Diagnostic System Check | Go to Step 3
3 | Inspect for poor connections/terminal tension at the DLC terminals 4 and 16. Refer to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to 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 the applicable Diagnostic System Check | --