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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 83 (Engine Controls Self-Diagnostics - 2.2L) >> Diagnostic Tests >> DTC P0141: Ho2S Heater Performance (Sensor 2) >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 GMC Sonoma and 2002 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. Connect the 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 millivolts? If no, go to next step. If yes, go to step  4.
  3. The condition that set this DTC is not present. This DTC may have been set by one of the following conditions; an intermittently open, grounded, high resistance or poor connections between HO2S and PCM circuits, or a defective HO2S. Repair as necessary. Did you find and correct the condition? If yes, go to step  14. If no, see DIAGNOSTIC AIDS .
  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 the ignition is ON while the engine is OFF. Is the HO2S voltage less than 20 millivolts? 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 the ignition is ON, with the 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 Multimeter (DMM) 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, OVERHAUL & 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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