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Home >> Chevrolet >> 2006 >> Cobalt LTZ >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 10 (Engine Controls - 2.4L - DTC P0010 To DTC P0341) >> Diagnostic Information & Procedures >> DTC P0120, P0122, P0123, P0220, P0222, P0223, or P2135 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
  1. Clear the DTCs with the scan tool. Operate the vehicle within the Conditions for Running the DTC, or within the conditions that you observed from the Freeze Frame/Failure Records.
  2. With the ignition ON, use a scan tool to observe the TP sensor 1 voltage with the accelerator pedal in the rest position. The voltage should be between 0.27-4.67 volts.
    • If more than 4.67 volts, test the low reference circuit for an open or a faulty ECM.
    • If less than 0.27 volt, test the TP sensor 1 signal circuit for a short to ground or a faulty ECM.
  3. With the ignition ON, observe the TP sensor 2 voltage with the accelerator pedal in the rest position with a scan tool. The voltage should be between 0.31-4.7 volts.
    • If more than 4.7 volts, test the low reference circuit for an open or a faulty ECM.
    • If less than 0.31 volt, test the TP sensor 2 signal circuit for a short to ground or a faulty ECM.
  4. With the ignition ON, use a scan tool to observe the DTCs.
  5. Disconnect the throttle body harness connector and verify the scan tool TP sensor 1 voltage is less than 0.1 volt.
    • If more than 0 volts, test the TP sensor 1 signal circuit for a short to voltage or a faulty ECM.
  6. With the throttle body harness connector still disconnected, verify the scan tool TP sensor 2 voltage is greater than 4.8 volts.
    • If less than 4.8 volts, test the TP sensor 2 signal circuit for a short to ground or a faulty ECM.
  7. With the ignition ON, test for 4.8-5.2 volts between both 5-volt reference circuits and the negative terminal of the battery.
    • If more than 5.2 volts, test both 5-volt reference circuits for a short to voltage or faulty ECM.
    • If less than 4.8 volts, test both the 5-volt reference circuits for an open or short to ground or a faulty ECM.
  8. Install a 3-amp fused jumper wire between the signal circuit and the 5-volt reference circuit of the TP sensor 1 and 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 an open, a short to ground, or a faulty ECM.
  9. Install a test lamp between the signal circuit and the negative terminal of the battery of the TP sensor 2 and verify the TP sensor 2 voltage is less than 0.1 volt.
    • If more than 0.1 volt, test the TP sensor 2 signal circuit for an open or a faulty ECM.
    • If test lamp illuminates, test the TP sensor 2 signal circuit for a short to voltage or faulty ECM.
  10. If all circuits test normal, replace the throttle body.

P2135 only

  1. With the ignition OFF, disconnect the throttle body harness connector and the ECM harness connector, and test for less than 5 ohms on each throttle position sensor circuit.
    • IF more than 5 ohms, repair the affected circuit or faulty ECM.
    • If less than 5 ohms, test for a short between TP sensor 1 signal circuit and TP sensor 2 signal circuit.
  2. If all circuits test normal, replace the throttle body.
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