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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1146 (Engine Controls And Fuel - 3.6L - DTC P0008 To DTC P0161) >> DTC P0121, P0122, P0123, P0221, P0222, or P0223 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, remove the fuse that supplies B+ to terminal X2-56 of the ECM.
  2. Disconnect the throttle body harness connector.
    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 between the low reference circuit terminal C 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 fuse that supplies B+ to terminal X2-56 of the ECM.
  5. Ignition ON, load test for 4.8-5.2 volts between the test lamp probe connected to the 5-volt reference circuit terminal E and ground.
      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.
    • If less than the specified range, test the 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 circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  6. Ignition ON, verify that the scan tool TP sensor 1 voltage parameter is less than 0.3 volt.
    • If greater than the specified value, test the 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 E and the TP sensor 1 signal circuit terminal D. Verify the scan tool TP sensor 1 voltage parameter is greater than 4.89 volts.
    • If less than the specified value, test the signal circuit for an open/high resistance or for a short to ground. If the circuit tests normal, replace the ECM.
  8. Verify the scan tool TP sensor 2 voltage parameter is greater than 4.97 volts.
    • If less than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
    9. IMPORTANT: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage.
  9. Connect a 3A fused jumper wire between the TP sensor 2 signal circuit terminal F and the low reference circuit terminal C. Verify the scan tool TP sensor 2 voltage parameter is less than 0.10 volt.
    • If greater than the specified value, test the signal circuit for an open/high resistance or for a short to voltage. If the circuit tests normal, replace the ECM.
  10. If all circuits test normal, replace the throttle body assembly.
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