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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 218 (ENGINE CONTROL SYSTEM - SELF-DIAGNOSTICS)DIAGNOSTIC TESTSDTC P0136: HO2S 2 CIRCUITDIAGNOSTIC 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 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Use scan tool to clear DTCs. Using scan tool, place the vehicle into CHECK MODE. See SERVICE BAY TESTS  under SELF-DIAGNOSTIC SYSTEM. Operate vehicle within freeze frame conditions as noted. Does DTC P0136 set? If yes, go to next step. If no, go to DIAGNOSTIC AIDS .
  3. Remove the rear floor console to gain access to the HO2S 2 electrical connector. Disconnect the HO2S 2 connector. Turn ignition switch to RUN position, with engine OFF. Set a DVOM to measure DC millivolts. Place the positive lead of the DMM on battery positive voltage, and the negative lead on the HO2S 2 sensor input circuit terminal (body harness side). Observe the HO2S 2 scan tool parameter. Is the voltage near 1155 mV? If yes, go to next step. If no, go to step  5.
  4. Connect a test light to battery voltage. Probe HO2S 2 sensor ground circuit terminal at the HO2S connector on the body harness side. Does the test light illuminate? If yes, go to step  7. If no, go to step  6.
  5. Check for an open or short in the HO2S 2 input circuit between the HO2S 2 and the PCM connector. Repair as necessary. Was a repair necessary? If yes, go to step  9. If no, go to step  8.
  6. Repair open in HO2S 2 ground circuit between HO2S 2 and ground point G104. After repair, go to step  9.
  7. Replace HO2S 2. After repair, go to step  9.
  8. Replace PCM. After repair, go to step  9.
  9. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within CONDITIONS FOR RUNNING DTC . Does DTC run and pass? If yes, go to next step. If no, go to step  2.
  10. Using a scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay at this time.
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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.