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.
SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 126 (ENGINE CONTROLS - SELF-DIAGNOSTICS - 4.0L)INSPECTION/MAINTENANCE PROCEDURESINSPECTION/MAINTENANCE HEATED OXYGEN SENSOR 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 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
- If I/M system check has been performed, go to next step. If I/M system check has not been performed, go to INSPECTION/MAINTENANCE SYSTEM CHECK .
- Preprogram scan tool with vehicle information before ignition is turned on. Ensure vehicle is operating within Conditions For Running this procedure. Set vehicle parking brake. Verify transmission is in Park. Turn OFF all of the accessories (e.g., A/C, blower fan, etc.). Start engine and allow it to idle for 2 minutes or until 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, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
- Refer to the Inspection/Maintenance (I/M) System DTC Table to determine which DTCs are required to run in order to complete this test. See INSPECTION/MAINTENANCE SYSTEM DTCS under INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE. With a scan tool, observe the Not Ran Since Code Cleared display. Determine which of the DTCs required for a YES status has not run. Enter the DTC number in the Specific DTC menu of the scan tool. Operate the vehicle within the Conditions for Running DTC. Repeat the procedure until the scan tool indicates the diagnostic test has run. Repeat this procedure for any additional required DTCs that have not run. With a scan tool, observe the I/M System Status display. Did the HO2S Heater System Status update to YES? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
- Using scan tool, observe emission related DTC portion of I/M system status display. If scan tool indicates any emission related DTCs, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If scan tool does not indicate any emission related DTCs, system is okay.
NOTE:
Whenever ignition is turned on, ignition voltage is supplied to HO2S heaters. After verifying enable criteria, turn ignition off for approximately 5 minutes to allow sensors to cool before continuing with test.
RENDER: 1.0x
NO RELATED
Recommended Tools & Savings
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.