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Home >> GMC >> 2006 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1737 (Automatic Transmission - ALLISON - DTC P0218 To DTC P0878) >> DTC P0843, P0848, or P0873 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 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 with a scan tool the TFP Switch 1, TFP Switch 2, and TFP Switch 3 parameters are High.
    • If not the specified value, test the affected pressure switch signal circuit for a short to ground. If circuits tests normal, replace the TCM.
  3. Connect a 3A fused jumper wire to the PS1 signal circuit terminal D to ground, PS2 signal circuit terminal F to ground, and PS3 signal circuit terminal E to ground. Verify with a scan tool the TFP Switch 1, TFP Switch 2, and TFP Switch 3 parameters change from High to Low when the signal circuit is grounded.
    • If not the specified value, test the affected pressure switch signal circuit for an open/high resistance. If circuits test normal, replace the TCM.
  4. Ignition OFF, connect the X175 harness connector to the transmission.
  5. Remove the pressure switch module from the valve body. Leave the internal wire harness connected to the pressure switch manifold. Refer to Pressure Switch Manifold Replacement .
  6. Connect a jumper wire to the base of the pressure switch module and ground.
  7. Ignition ON, engine OFF, gently push on the PS1, PS2, and PS3 switches with the eraser end of a pencil. Verify with a scan tool that the TFP Switch 1, TFP Switch 2, and TFP Switch 3 parameters changed from High to Low when the pressure switch is pushed.
    • If not the specified value, test the internal wire harness circuits for an open/high resistance. If the circuits test normal, replace the pressure switch module.
  8. If all circuits test normal, remove the control valve body. Refer to Control Valve Body Replacement .
  9. Perform the Control Valve Body Assembly Disassemble and Control Valve Body Cleaning and Inspection .
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