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Home >> Pontiac >> 2006 >> G6 GTP, 2D Convertible >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - 3.9L - DTC P2077 To DTC P2A04 >> DTC P2077 or P2078 >> Circuit/System Testing

Circuit/System Testing

  1. Ignition ON engine OFF.
  2. Command the IMT valve ON and OFF. The IMT valve Command parameter should transition from open to closed and the IMT valve Feedback parameter should transition from 18.4-25.2 percent to 76.3-83.2 percent.


  1. Ignition OFF, disconnect the IMT valve harness connector at the IMT valve.
  2. Test for less than 1 ohm of resistance between the IMT valve ground circuit terminal B and ground.
    • If greater than the specified value, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify that a test lamp illuminates between the IMT valve ignition 1 voltage circuit and ground.
    • If the test lamp does not illuminate, test the IMT valve ignition 1 voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the fuse for the IMT valve ignition 1 voltage circuit is open, test or replace the IMT valve.
  4. Connect a test lamp between the IMT valve control circuit terminal C and the IMT valve ignition 1 voltage circuit.
  5. Command the IMT valve ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the IMT valve control circuit for a short to ground. If the circuit tests normal, replace the ECM.
    • If the test lamp is always OFF, test the IMT valve control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  6. Ignition ON, test for 4-6 volts between the IMT valve signal circuit terminal D and ground.
    • If less than the specified range, test the IMT valve signal 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 IMT valve signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  7. Install a 3A fused jumper wire between the IMT valve signal circuit terminal D and ground. Verify the scan tool IMT valve Feedback parameter transitions from 0-100 percent.
    • If parameter does not change, test the IMT valve signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
  8. If all circuits test normal, test or replace the IMT valve.
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