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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 103 (Engine Controls Self-Diagnostics - 2.2L) >> Diagnostic Tests >> DTC P0141: Ho2S 2 Heater Circuit (SOHC) >> Diagnostic Procedures

Diagnostic Procedures

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  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
    2. NOTE: The HO2S must be cool before proceeding with this test. The ignition must remain OFF for at least one-half hour before proceeding with this test.
  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 2 voltage. Monitor the HO2S voltage for 2 minutes. Does the HO2S voltage increase or decrease from the initial voltage by at least 150 millivolts? If yes, go to next step. If no, 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 or high resistance, HO2S high signal circuit, a low signal circuit, an intermittently open or high resistance in HO2S heater ignition 1 voltage, or a heater ground circuit. A faulty HO2S or PCM connector terminal contact, or a defective HO2S. Repair any of the conditions as necessary. Did you find and correct the condition? If yes, go to step  15. If no, go to DIAGNOSTIC AIDS .
  4. Turn ignition off. Disconnect HO2S connector for the sensor that applies to this DTC. Connect a test light between the HO2S heater ignition 1 voltage circuit and the 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 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 for the sensor that applies to this DTC. Ensure that 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 known-good ground. Ensure that the ignition is ON while the engine is OFF. Does the test light illuminate? If yes, go to step  10. If no, go to step  11.
  7. Turn ignition off. Remove the jumpers from the PCM connector containing the HO2S high and low signal circuits. Use a Digital Multimeter (DMM) in order to measure the continuity of the following circuits between the PCM connector terminal and HO2S connector terminal at the engine harness side, the HO2S high signal circuit, or the HO2S low signal circuit. Does the resistance measure less than 5 ohms? If yes, go to step  13. If no, go to step  12.
  8. Inspect for poor connections at the harness connector of the HO2S sensor. Did you find and correct the condition? If yes, go to step  15. If no, go to next step.
  9. Replace HO2S. When complete, go to step  15.
  10. Repair open HO2S heater ground circuit. After repairs, go to step  15.
  11. Repair 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  15.
  12. Repair circuit that measured high resistance. After repairs, go to step  15.
  13. Inspect for proper PCM terminal contact. Repair connectors as necessary. Did you find and correct the condition? If yes, go to step  15. If no, go to next step.
  14. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL, OVERHAUL & INSTALLATION article. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE REPROGRAMMING  under PROGRAMMING. After replacing PCM, go to next step.
  15. 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.
  16. 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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