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Home >> Saturn >> 2009 >> Sky Red Line, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls And Fuel - 2.0L - DTC P0010 To DTC P0238 >> DTC P0121, P0122, or P0123 >> Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the throttle body. Allow sufficient time for the ECM to completely power down.
  2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal C and ground.
    • If greater than 5 ohms, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal E and ground.
    • If less than 4.8 volts, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
    • If greater than 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  4. Verify the scan tool TP sensor 1 voltage is less than 0.1 volt.
    • If greater than 0.1 volt, test the signal circuit terminal D for a short to voltage. If the circuit tests normal, replace the ECM.
  5. Install a 3A fused jumper wire between the signal circuit terminal D and the 5-volt reference circuit terminal E of the TP sensor 1, verify the TP sensor 1 voltage is greater than 4.8 volts.
    • If less than 4.8 volts, test the TP sensor 1 signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
  6. Ignition OFF, disconnect the harness connector at the ECM.
  7. Test for less than 5 ohms on the TP sensor circuits between the following terminals:
    • ECM X1 5-volt reference circuit terminal 39 to terminal E.
    • ECM X1 signal circuit terminal 90 to terminal D.
    • If greater than 5 ohms, repair the affected circuit.
  8. Test for infinite resistance between TP sensor 1 signal circuit terminal D and TP sensor 2 signal circuit terminal F.
    • If less than infinite resistance, repair the short between TP sensor 1 signal circuit and TP sensor 2 signal circuit.
  9. If all circuits test normal, replace the throttle body.
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