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Home >> Chevrolet >> 2006 >> Impala LTZ >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - 3.9L - DTC P0442 To DTC P2A01 >> DTC P2077 or P2078 >> Circuit/System Testing
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Circuit/System Testing

  1. Monitor the scan tool for any other DTCs.
    • If DTC P0660 is set, diagnose that DTC first. Refer to DTC P0660 .
  2. Ignition ON, disconnect the IMT valve harness connector and measure for 0.5 volt on the variable tuning signal circuit and ground.
    • If less than 0.5 volt, test the variable tuning signal circuit for an open or high resistance, short to ground, or a faulty control module.
    • If more than 0.6 volt, test the variable tuning signal circuit for a short to voltage or a faulty control module.
  3. Measure for 5.0 volts on the IMT fan position signal circuit at the IMT valve harness connector and ground.
    • If more than 5 volts, test the IMT fan position signal circuit for a short to voltage.
    • If less than 5 volts, test the IMT fan position signal circuit for an open, high resistance, or short to ground.
    • If all circuits test OK, replace the IMT valve.
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