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 18 (BODY CONTROL MODULES)SELF-DIAGNOSTIC SYSTEMINSPECTION/MAINTENANCE DIAGNOSTIC SYSTEM CHECK
2003 Chevrolet TrailBlazer 4.2 S, 4WD
Inspection/Maintenance Diagnostic System Check
2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Inspection/Maintenance Diagnostic System Check
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2002 GMC Savana, 2002 Chevrolet Chevy Express, 2001 GMC Savana Special, 2001 GMC Savana Camper Special, and 2001 GMC Savana. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
Many DTC related repairs will instruct the technician to clear DTC information. This procedure will reset all Inspection/Maintenance (I/M) system status indicators to NO, and require performing the I/M complete system set procedure.
- If engine controls diagnostic system check has been performed, go to next step. If engine controls diagnostic system check has not been performed, go to ENGINE CONTROLS DIAGNOSTIC SYSTEM CHECK . Repair any DTCs or driveability concerns which would prevent I/M system status tests from completing. If no DTCs or driveability concerns exist, go to next step. If any DTCs or driveability concerns were found and repaired, go to step 3 .
- Review any service bulletins for software updates which may prevent I/M readiness. Perform any reprogramming or repairs indicated by service bulletins. If a reprogramming or repair service was not required, go to next step. If a reprogramming or repair service was required, see INSPECTION/MAINTENANCE SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
- Using scan tool, observer I/M system status display. If more than one test indicates a NO status, go to If a reprogramming or repair service was required, see INSPECTION/MAINTENANCE SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. If no or only one test indicate a NO status, go to appropriate I/M system set procedure for indicated system. See INSPECTION/MAINTENANCE SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.
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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.