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Home >> Saturn >> 2006 >> Relay 3.9 1, FWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - 3.9L - DTC P0442 To DTC P2A01 >> DTC P2A01 >> Circuit/System Testing
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Circuit/System Testing

  1. Disconnect the affected HO2S.
  2. Ignition ON, verify the applicable scan tool HO2S parameter is approximately 450 mV.
    • If more than approximately 450 mV, test the high signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    • If less than approximately 450 mV, test the high signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
  3. Ignition ON, measure for more than 2 mV from the affected HO2S low signal circuit to ground.
    • If less than 2 mV, test the affected HO2S low signal circuit for a short to ground or an open/high resistance.
    • If the circuit tests normal, replace the ECM.
  4. Install a 3-amp fused jumper wire at the high signal circuit terminal. Toggle the jumper wire between the low signal circuit terminal and battery voltage. Verify the appropriate scan tool HO2S parameter toggles between 0 mV, and more than 1,000 mV.
    • If the appropriate scan tool HO2S parameter does not toggle correctly, test the high signal circuit for an open/high resistance. If the circuit tests normal, test the low signal circuit for a short to voltage.
    • If the circuit tests normal, replace the ECM.
  5. If all circuits test normal, replace the appropriate HO2S.
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