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 266 (BODY CONTROL MODULES)SELF-DIAGNOSTIC SYSTEMHORNS DIAGNOSTIC SYSTEM CHECK
2003 Chevrolet TrailBlazer 4.2 S, 4WD
Horns Diagnostic System Check
2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Horns Diagnostic System Check
WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
- Connect scan tool to Data Link Connector (DLC). DLC is located below driver side of instrument panel, near steering column. If scan tool powers up, go to next step. If scan tool does not power up, perform TEST A: SCAN TOOL DOES NOT POWER UP under SYSTEM TESTS.
- Turn ignition switch to RUN position. Using scan tool, attempt to communicate with Dash Integration Module (DIM). If scan tool communicates with DIM, go to next step. If scan tool does not communicate with DIM, perform TEST B: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE under SYSTEM TESTS.
- Using scan tool, select DISPLAY DTCs function for DIM. If scan tool displays any DTCs, go to next step. If scan tool does not display any DTCs, repair horns by symptom. See STEERING COLUMN SWITCHES - AURORA article.
- If scan tool does not display any DTCs which begin with "U", go to next step. If scan tool displays any DTCs which begin with "U", perform TEST B: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE under SYSTEM TESTS.
- If scan tool does not display DTCs B1007 or B1009, go to next step. If scan tool displays DTCs B1007 or B1009, perform appropriate test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
- If scan tool displays DTC B1327, perform appropriate test. See DTC B1327: BATTERY/SOURCE VOLTAGE LOW under DIAGNOSTIC TESTS in GENERATORS & REGULATORS - AURORA article in ELECTRICAL. If scan tool does not display DTC B1327, perform appropriate test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
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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.