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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. Allow engine to idle at operating temperature. Observe HO2S 2 voltage parameter using a scan tool. Clear DTC and record freeze frame/failure records data if HO2S 2 voltage is fixed at bias voltage. Vary engine speed from idle to 3000 RPM several times within 5 seconds. Does HO2S 2 voltage fluctuate greater than and less than 375-475 mV? If yes, go to next step. If no, go to step  4.
  3. Observe freeze frame/failure records data for this DTC. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within CONDITIONS FOR RUNNING DTC  or as close to freeze frame/failure records data observed. Does the DTC fail this ignition? If yes, go to next step. If no, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.
  4. Disconnect HO2S 2 4-pin harness connector. Turn ignition switch to RUN position, engine off. Connect a 3-amp fused jumper wire between HO2S 2 low signal circuit and a good ground. Connect a 3-amp fused jumper wire between the HO2S 2 high signal circuit and a good ground. Observe HO2S 2 voltage parameter using scan tool. Does HO2S 2 voltage measure less than 25 mV? If yes, go to step  7. If no, go to next step.
  5. With the ignition OFF, disconnect PCM harness connectors. Leave HO2S 2 disconnected. Measure resistance of HO2S 2 high signal circuit. Measure resistance of HO2S 2 low signal circuit. Is resistance 0-5 ohms? If yes, go to step  9. If no, go to next step.
  6. Repair appropriate signal circuit that has an open or high resistance condition. After repair, go to step  12.
  7. Check for the following conditions that may affect HO2S operation:
    • HO2S for contamination.
    • Chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring.
    • Exhaust system leaks or restrictions.
    • Chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring.
    • Exhaust system leaks or restrictions.
    • EVAP canister purge.
    • Proper fuel pressure.
    Did you find and correct the condition? If yes, go to step  12. If no, go to next step.
  8. Check for poor connections at HO2S 2 connector. Did you find and correct the condition? If yes, go to step  12. If no, go to step  10.
  9. Check for poor connections at PCM harness connectors. Did you find and correct the condition? If yes, go to step  12. If no, go to step  11.
  10. Replace HO2S 2. After repair, go to step  12.
  11. Turn ignition off. Replace PCM. After repair, go to next step.
  12. 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.
  13. 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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