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Home >> Buick >> 2008 >> Allure CXL >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 8 (Engine Control System & Fuel System - 5.3L - DTC P0016 To DTC P0358) >> DTC P0120, P0122, P0123, P0220, P0222, P0223, or P2135 >> Circuit/System Testing

Circuit/System Testing

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  1. Ignition OFF, disconnect the harness connector at the throttle body.
  2. Ignition OFF for 90 seconds, test for less than 5 ohms between the low reference circuit terminals 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 5-volt reference circuit terminal E and ground.
    • If less than 4.8 volts, test 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. Verify the scan tool TP sensor 2 voltage is greater than 4.8 volts.
    • If less than 4.8 volts, test the signal circuit terminal F for a short to ground. If the circuit tests normal, replace the ECM.
  6. 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.
  7. Install a 3A fused jumper wire between the signal circuit terminal F and the low reference circuit terminal C of the TP sensor 2. Verify that the TP sensor 2 voltage is less than 0.1 volt.
    • If greater than 1.0 volt, test the TP sensor 2 signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  8. Ignition OFF for 90 seconds, disconnect the harness connector at the ECM.
  9. Test for less than 5 ohms on all TP sensor circuits between the following terminals:
    • ECM X2 signal circuit terminal 64 and the throttle body connector terminal D
    • ECM X2 signal circuit terminal 66 and the throttle body connector terminal F
    • ECM X2 5-volt reference circuit terminal 44 and the throttle body connector terminal E
    • If greater than 5 ohms, repair the affected circuit for open/high resistance.
  10. Test for infinite resistance between TP sensor 1 signal circuit terminal D and TP sensor signal circuit terminal F.
    • If less than infinite resistance, repair the short between TP sensor 1 signal circuit and TP sensor 2 signal circuit.
  11. If all circuits test normal, replace the throttle body.
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