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Home >> GMC >> 2003 >> Yukon Denali >> Repair and Diagnosis >> External Pages >> Different car >> Section 457 (Automatic Transmission - 4L80-E/4L85-E Diagnosis (DTC P0218 To DTC P2771)) >> Diagnosis >> DTC P2771 >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 GMC Yukon XL, 2004 Chevrolet Suburban, and 2004 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 3:  This step tests for a short to ground in the signal circuit.
  2. 4:  This step tests for an open in the signal circuit, a faulty transfer case control module, active transfer case vehicles, or transfer case switch, non-active transfer case vehicles.
DTC P2771

Step Action Value(s) Yes No
1 Did you perform the Diagnostic System Check - Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls in Engine Controls - 6.0L or Diagnostic System Check - Engine Controls in Engine Controls - 8.1L
2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
    3. IMPORTANT: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info Function erases the Freeze Frame and Failure Records from the PCM.
  3. Record the Freeze Frame and Failure Records.
  4. Clear the DTCs.
  5. Place the transmission in NEUTRAL.
  6. Select 4WD, then 4WD Low on the transfer case selector lever.
Does the 4WD Low on the scan tool display Disabled when 4WD is selected, then Enabled when 4WD Low is selected?		 - Go to Intermittent Conditions in Engine Controls - 6.0L or Intermittent Conditions in Engine Controls - 8.1L Go to Step 3 
3 
  1. Turn OFF the ignition switch.
  2. Disconnect the active transfer case control module connector, for active transfer case vehicles, or the transfer case switch connector, for non-active transfer case vehicles.
  3. Turn ON the ignition, with the engine OFF.
Does the 4WD Low on the scan tool indicate Enabled?		 - Go to Step 6  Go to Step 4 
4 
  1. Ground C1-B5 of the active transfer case control module connector, for active transfer case vehicles, or terminal B of the transfer case switch connector, for non-active transfer case vehicles, to ground.
  2. Ensure that the scan tool displays 4WD Low.
Does 4WD Low on the scan tool indicate Enabled when the signal circuit is grounded?		 - Go to Step 5  Go to Step 7 
5 Replace the active transfer case control module on the active transfer case vehicles, or the transfer case switch on the non-active transfer case vehicles.
Refer to Transfer Case Shift Control Module Replacement in Transfer Case - BW 4482-NR4 or Transfer Case Shift Control Module Replacement in Transfer Case - NVG 246-NP8, for active transfer case vehicles. Refer to Transfer Case Shift Control Switch Replacement in Transfer Case - BW 4482-NR4 or Transfer Case Shift Control Switch Replacement in Transfer Case - NVG 246-NP8 for non-active transfer case vehicles.
Did you complete the replacement?		 - Go to Step 9  -
6
  1. Test the 4WD Low signal circuit for a short to ground.
  2. Repair the circuit if necessary.
Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.Did you find and correct the condition?		 - Go to Step 9  Go to Step 8 
7
  1. Test the 4WD Low signal circuit for an open.
  2. Repair the circuit if necessary.
Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.Did you find and correct the condition?		 - Go to Step 9  Go to Step 8 
8 Replace the PCM.
Refer to Powertrain Control Module (PCM) Replacement in Engine Controls - 6.0L or Powertrain Control Module (PCM) Replacement in Engine Controls - 8.1L.
Did you complete the replacement?		 - Go to Step 9  -
9 Perform the following procedure in order to verify the repair:
  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions:
    • Select 4WD Low on the 4WD selector and drive the vehicle. The transfer case gear ratio must be 2.68-2.76 for 1 second in 4th gear with the TCC locked.
    • Select 4WD on the selector and drive the vehicle. The gear ratio must be 0.95-1.05 for 0.5 second in any one gear.
  4. Select Specific DTC.
  5. Enter DTC P2771.

Has the test run and passed?		 - Go to Step 10  Go to Step 2 
10 With the scan tool, observe the stored information, capture info and DTC info.
Does the scan tool display any DTCs that you have not diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 6.0L or Diagnostic Trouble Code (DTC) List in Engine Controls - 8.1L System OK
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