For 1990-2009 cars

### Circuit Description

The data link connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated by an industry-wide standard, and is required to provide the following:

• | Scan tool power battery positive voltage at terminal 16

• | Scan tool power ground at terminal 4

• | Common signal ground at terminal 5

The scan tool will power up with the ignition OFF. Some modules, however, will not communicate unless the ignition is ON and the power mode master (PMM) module sends the appropriate power mode message.

### Test Description

The number below refers to the step number on the diagnostic table.

1. If 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
--- | --- | --- | ---
Schematic Reference: Data Communication Schematics Connector End View Reference: Data Communication Connector End Views
1 | Test the battery positive voltage circuit of the data link connector (DLC) for an open or a short to ground. Refer to the following:

• | Circuit Testing

• | Wiring Repairs

Did you find and correct the condition?

Go to Diagnostic System Check - Vehicle

Go to Step 2

2 | Test the ground circuits of the DLC for an open or high resistance. Refer to the following:

• | Circuit Testing

• | Wiring Repairs

Did you find and correct the condition?

Go to Diagnostic System Check - Vehicle

Go to Step 3

3 | Inspect for poor connections and terminal tension at the DLC. Refer to the following:

• | Testing for Intermittent Conditions and Poor Connections

• | Connector Repairs

Did you find and correct the condition?

Go to Diagnostic System Check - Vehicle

Go to Step 4

4 | The scan tool or the CANdi module may be malfunctioning. Refer to the scan tool user guide. Did you obtain a properly operating scan tool and CANdi module? | Go to Diagnostic System Check - Vehicle | --