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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. NOTE: If engine has just been operating, allow engine to cool until near bias voltage is observed on scan tool before proceeding.
  2. Turn ignition switch to RUN position, engine off. Monitor HO2S 2 voltage on scan tool. Does HO2S 2 voltage go to greater than or less than the previously stabilized voltage, by at least as much as 100 mV within 2 minutes? If yes, go to next step. If no, go to step  4.
  3. Observe freeze frame/failure records data for this DTC. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within CONDITIONS FOR RUNNING DTC  or as close to freeze frame/failure records data observed. Does DTC fail this ignition? If yes, go to next step. If no, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.
    4. NOTE: Ensure test light is connected to a good ground.
  4. Disconnect HO2S 2 4-pin harness connector. Turn ignition switch to RUN position, engine off. Connect a test light between HO2S 2 heater ignition voltage circuit, in harness side of HO2S connector, and ground. Does the test light illuminate? If yes, go to next step. If no, go to step  7.
  5. Turn ignition OFF. Connect a test light between HO2S 2 heater ignition voltage circuit, in harness side of HO2S connector, and HO2S 2 heater ground circuit. Turn ignition switch to RUN position, engine off. Does test light illuminate? If yes, go to next step. If no, go to step  10.
    6. NOTE: The heater element resistance will vary according to HO2S temperature. A hot HO2S heater element will have a higher resistance than at room temperature.
  6. Turn ignition OFF. Leave HO2S connector disconnected. Allow engine to cool for at least 15 minutes. Measure HO2S 2 heater resistance at HO2S 2 pigtail connector using a Digital Multimeter (DMM). Resistance should be 2-20 ohms? If yes, go to next step. If no, go to step  11.
  7. Check HO2S 2 heater ignition voltage circuit for an open fuse. Did you find an open fuse? If yes, go to next step. If no, go to step  9.
  8. Locate and repair short to ground in HO2S 2 heater ignition voltage circuit and replace fuse. After repair, go to step  13.
  9. Repair open or high resistance condition in HO2S 2 heater ignition voltage circuit. After repair, go to step  13.
  10. Repair open or high resistance condition in HO2S 2 heater ground circuit. After repair, go to step  13.
  11. Before continuing, Check for poor connections at HO2S 2 connector. Did you find and correct the condition? If yes, go to step  13. If no, go to next step.
  12. Replace HO2S 2. After repairs, go to next step.
  13. Use scan tool to clear DTCs. Turn ignition OFF for 30 seconds. Start engine. Operate vehicle within CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  14. Using a scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that have not been diagnosed? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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