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 279 (ENGINE CONTROLS - SELF-DIAGNOSTICS - 2.2L)DRIVE CYCLESINSPECTION/MAINTENANCE HEATED OXYGEN SENSOR (HO2S) HEATER SYSTEM SET PROCEDUREDIAGNOSTIC PROCEDURES
2003 Chevrolet TrailBlazer 4.2 S, 4WD
Diagnostic Procedures
2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
- Did you perform the Inspection/Maintenance (I/M) System Check? If yes, go to next step. If no, go to INSPECTION/MAINTENANCE SYSTEM CHECK .
- Preprogram the scan tool with the vehicle information before the ignition is turned on. Ensure vehicle is within the Conditions for Running. See CONDITIONS FOR RUNNING . Set the vehicle parking brake. Verify transmission is in Park (A/T) or Neutral (M/T). Turn off all of the accessories (e.g., A/C, blower fan, etc.). Start and operate engine at idle for 2 minutes or until the I/M System Status indicator updates to YES. Did the HO2S Heater System Status update to YES? If yes, go to step 5. If no, go to next step.
- Using scan tool, observe DTC information. Does the scan tool indicate any failed DTCs? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go next step.
- Using scan tool, observe the NOT RAN SINCE CODE CLEARED display. Determine which of the DTCs required for a YES status has not run. Operate vehicle within the Conditions For Running DTC. See CONDITIONS FOR RUNNING . Monitor status of DTCs that are necessary to complete the test in the NOT RAN SINCE CODE CLEARED display of scan tool. Repeat procedure until scan tool indicates that all the necessary DTC diagnostic tests have run. Using scan tool, observe I/M System Status display. Did the HO2S Heater System Status update to YES? If yes, go to next step. If no, go to DIAGNOSTIC AIDS .
- Using scan tool, observe emission related DTC portion of I/M System Status display. Does the scan tool indicate any emission related DTCs set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
NOTE:
Whenever the ignition is turned on, ignition positive voltage is supplied to the HO2S heaters. After verifying the enable criteria, turn off the ignition for about 5 minutes to allow the sensors to cool before continuing with the test.
NOTE:
Refer to INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE to determine which DTCs are required to run in order to complete this test.
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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.