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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 263 (ENGINE CONTROLS SELF-DIAGNOSTICS - 2.2L)DIAGNOSTIC TESTSDTC P0141: HO2S HEATER PERFORMANCE (SENSOR 2)DIAGNOSTIC 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 GMC Sonoma and 2003 Chevrolet S10 Pickup. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
    NOTE: If engine has been operating, turn ignition off and allow engine to cool down for about 1/2 hour before proceeding with diagnosis.
    2. NOTE: The HO2S must be cool before proceeding with a diagnosis. The ignition must remain OFF for at least one-half hour before proceeding with a diagnosis.
  2. Connect scan tool. Set up the scan tool with the proper vehicle identification information prior to turning the ignition on. Turn ignition on, with engine off. As quickly as possible observe and record the HO2S voltage for the sensor that applies to this DTC. Monitor the HO2S voltage for two minutes. Does the HO2S voltage increase or decrease from the initial voltage by at least 150 mV? If no, go to next step. If yes, go to step  4 .
  3. Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC  . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to next step. If no, problem is intermittent.
  4. Turn ignition off. Disconnect the HO2S connector. Connect a test light between the HO2S heater ignition 1 voltage circuit and ground circuit terminals at the engine harness side. Turn ignition on, with engine off. Does the test light illuminate? If yes, go to next step. If no, go to step  6 .
  5. Disconnect the test light. Jumper the HO2S low signal circuit terminal to a known-good ground. Jumper the HO2S high signal circuit terminal to a known-good ground. Use a scan tool in order to monitor the HO2S voltage. Ensure ignition is on, with engine off. Is the HO2S voltage less than 20 mV? If yes, go to step  8 . If no, go to step  7 .
  6. Connect the test light between the HO2S heater ignition 1 voltage circuit terminal at the engine harness side and a clean body ground. Ensure ignition is on, with engine off. Does the test light illuminate? If yes, go to step  9 . If no, go to step  10 .
  7. Turn ignition off. Remove the jumpers from the PCM connector containing the HO2S high signal and low signal circuits. Use a Digital Volt-Ohmmeter (DVOM) in order to measure the continuity of the HO2S high signal circuit and then the HO2S low signal circuit between the PCM connector terminal and the HO2S connector terminal at the engine harness side. Does the resistance measure less than 5 ohms? If yes, go to step  12 . If no, go to step  11 .
  8. Replace HO2S. After replacing sensor, go to step  14 .
  9. Turn ignition off. Repair open in Black wire to ground connector. Repair as necessary. After repairs, go to step  14 .
  10. Repair the lack of voltage on the HO2S heater ignition 1 voltage circuit. If the fuse is blown, repair the short to ground on the circuit. A blown fuse or lack of voltage to the fuse may cause other DTCs or symptoms to be present. After repairs, go to step  14 .
  11. Repair circuit with high resistance. Repair as necessary. After repairs, go to step  14 .
  12. Check for poor connections at PCM. Repair as necessary. After repairs, go to step  14 . If connections are okay, go to next step.
  13. Replace PCM. See appropriate REMOVAL & INSTALLATION article. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  14. Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC  . Does the DTC run and pass? If yes, go to next step. If no, go to step  2 .
  15. With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, system is okay.
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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.