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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1379 (Automatic Transmission - ALLISON - DTC P0880 To DTC P2771) >> DTC P2727, P2729, or P2730 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the X175 harness connector at the transmission.
  2. Ignition ON, engine OFF, verify that a test lamp illuminates between the B+ circuit terminal L and ground.
    • If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the TCM.
  3. Connect a test lamp between the control circuit terminal M and the B+ circuit terminal L.
  4. Command the PC Solenoid 1 ON and OFF with a scan tool and verify the PC Sol. 1 Pressure Command parameter changes from 1600 kPa (232 psi) to 0 kPa (0 psi). The test lamp should turn ON and OFF when changing between the commanded states.
    • If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the TCM.
    • If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the TCM.
  5. Remove the transmission oil pan. Refer to Oil Pan Replacement .
  6. Test the transmission internal PCS1, B+, and control circuits for a short to voltage, short to ground, or an open/high resistance.
    • If the circuits test normal, test or replace the PCS1 solenoid.
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