Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 945 (DATA LINK COMMUNICATION SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESSCAN TOOL DOES NOT POWER UPTEST DESCRIPTION
2003 Chevrolet TrailBlazer 4.2 S, 4WD
Test Description
2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Test Description
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The number below refers to the step number on the diagnostic table.
- 4: If the battery positive voltage and ground circuits of the DLC are functioning properly. The malfunction must be due to the scan tool.
Scan Tool Does Not Power Up
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: Data Link Connector (DLC) Schematics Connector End View Reference: Data Link Communications 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 Circuit Testing
or Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Control Module References in Body Control System for the applicable Diagnostic System Check | Go to Step 2 |
| 2 | Test the ground circuit from pin 4 of the DLC for an open or high resistance. Refer to Circuit Testing
or Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Control Module References in Body Control System for the applicable Diagnostic System Check | Go to Step 3 |
| 3 | Inspect for poor connections and terminal tension at the DLC. Refer to Testing for Intermittent Conditions and Poor Connections
or Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Control Module References in Body Control System for the 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 Control Module References in Body Control System for the applicable Diagnostic System Check | - |
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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.