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Home >> GMC >> 2006 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1727 (Automatic Transmission - 4L60-E/4L65-E/4L70-E - DTC P0218 To DTC P2771) >> DTC P2771 >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different car, the 2010 GMC Sierra and 2010 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
    NOTE: It may be necessary to drive the vehicle slightly forward to engage 4LO on the transfer case.
  1. Key ON. Engine OFF.
  2. Parking brake ON. Transmission in Neutral.
  3. Using the transfer case data display functionality of the scan tool, verify that the "Mode Switch Selected", "Transfer Case Position" and corresponding "Indicator Light" parameters all match when using the TCSCS to change modes.
  4. Using the TCM - transmission data display functionality of the scan tool, verify that the "4WD Low parameter", reads Enabled/Disabled when using the TCSCS to go In/Out of 4WD Low.
    • If the parameter does not perform as specified, suspect a Replicated TOS Signal circuit or TCM condition.
  5. Using the ECM - auto. transmission data display functionality of the scan tool, verify that the "4WD Low parameter", reads Enabled/Disabled when using the TCSCS to go In/Out of 4WD Low.
    • If the parameter does not perform as specified, suspect a Replicated TOS Signal circuit or ECM condition.
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