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Check for open or short to ground in Orange wire between instrument panel fuse block and Data Link Connector (DLC) terminal No. 16. See Fig 1 . If Orange wire is okay, go to next step. If Orange wire is not okay, repair as necessary. After repair, perform appropriate diagnostic system check.
Check for open in Black wire between ground and DLC terminal No. 4. If Black wire is okay, go to next step. If Black wire is not okay, repair circuit as necessary. Perform appropriate diagnostic system check. See appropriate article for malfunctioning system.

Fig 1: Identifying Data Link Connector Terminals
Courtesy of GENERAL MOTORS CORP.
Check for poor terminal contact between scan tool and DLC terminals No. 4 and 16. If terminal contact is okay, go to next step. If terminal contact is not okay, repair as necessary. Perform appropriate diagnostic system check. See appropriate article for malfunctioning system.
Scan tool may be malfunctioning. Check scan tool manual for diagnostic procedures. After repair, perform appropriate diagnostic system check with known good scan tool. See appropriate article for malfunctioning system.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Test A: Scan Tool Does Not Power Up: Testing

Use the Manual With the Right Hardware

When to See a Mechanic

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