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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1373 (Automatic Transmission - ALLISON - DTC P0218 To DTC P0878) >> DTC P0877 or P0878 >> 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. Inspect the transmission fluid level. Refer to Transmission Fluid Check .
  2. Ignition OFF, disconnect the X175 harness connector at the transmission.
  3. Ignition ON, engine OFF, verify with a scan tool the TFP Switch 4 parameter is High.
    • If not the specified value, test the PS4 signal circuit for a short to ground. If circuit tests normal, replace the TCM.
  4. Ignition ON, connect a 3A fused jumper wire to the PS4 signal circuit terminal K to ground. Verify with a scan tool the TFP Switch 4 parameter changes from High to Low when the signal circuit is grounded.
    • If not the specified value, test the PS4 signal circuit for 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 Pressure Switch 4 signal circuit for a short to ground or open/high resistance.
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