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Home >> Buick >> 2008 >> Allure CXL >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 7 (Engine Control System & Fuel System - 3.6L - DTC P0008 To DTC P0333) >> DTC P0121, P0122, P0123, P0221, P0222, or P0223 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
  1. Ignition OFF, remove the fuse that supplies B+ to terminal X2-36 of the ECM.
  2. Disconnect the harness connector at the throttle body.
    3. IMPORTANT: The control module or the sensor may be damaged if the circuit is shorted to battery positive voltage.
  3. Test for less than 5 ohms of resistance between the low reference circuit terminal 6 and ground.
    • If greater than the specified range, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  4. Install the fuse that supplies B+ to terminal X2-36 of the ECM.
    5. IMPORTANT: The 5-volt reference circuits are internally and externally connected at the ECM. Other component DTCs may be set. If other DTCs are set, review the electrical schematic and diagnose the applicable circuits and components.
  5. Ignition ON, load test for 4.8-5.2 volts between the 5-volt reference circuit terminal 2 and ground.
    • If less than the specified range, 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 the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  6. Ignition ON, verify that both scan tool TP sensor 1 and TP sensor 2 voltage parameters are less than 0.3 volts.
    • If greater than the specified range, test the appropriate signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  7. Connect a 3A fused jumper wire between the 5-volt reference circuit terminal 2 and the TP sensor 1 signal circuit terminal 1. Verify the scan tool TP sensor 1 voltage parameter is greater than 4.89 volts.
    • If less than the specified range, test the signal circuit for an open/high resistance or for a short to ground. If the circuit tests normal, replace the ECM.
    8. IMPORTANT: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage.
  8. Connect a 3A fused jumper wire between the TP sensor 2 signal circuit terminal 4 and the 5 volt reference circuit terminal 2. Verify the TP sensor 2 voltage parameter is greater than 4.89 volts.
    • If less than the specified range, test the signal circuit for an open/high resistance or for a short to ground. If the circuit tests normal, replace the ECM.
  9. If all circuits test normal, replace the throttle body assembly.
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