Test Description

WARNING: This page is about a different car, the 2006 GMC Sierra, 2006 GMC Cab & Chassis Sierra, 2006 Chevrolet Silverado, and 2006 Chevrolet Cab & Chassis Silverado. 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.

3: This step tests for a short to ground in the 4WD Low signal circuit.
4: This step tests for an open in the 4WD Low 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	Yes	No
1	Did you perform the Diagnostic System Check - Vehicle?	Go to Step 2	Go to Diagnostic System Check - Vehicle
2	Install a scan tool. Turn ON the ignition, with the engine OFF. 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. Record the Freeze Frame and Failure Records. Clear the DTCs. Place the transmission in NEUTRAL. 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 Testing for Intermittent Conditions and Poor Connections	Go to Step 3
3	Turn OFF the ignition switch. Disconnect the active transfer case control module connector, active transfer case vehicles, or the transfer case switch connector, non-active transfer case vehicles. 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	Ground C1-B5 of the active transfer case control module connector, active transfer case vehicles, or terminal B of the transfer case switch connector, non-active transfer case vehicles, to ground. Ensure that the scan tool displays 4WD Low. Does 4WD Low on the scan tool indicate Enabled when the 4WD Low 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. For active transfer case vehicles, refer to one of the following replacement procedures: Transfer Case Shift Control Module Replacement in Transfer Case - NVG 246-NP8 Transfer Case Control Lever Replacement in Transfer Case - NVG 261-NP2 Transfer Case Shift Control Module Replacement in Transfer Case - NVG 263-NP1 For non-active transfer case vehicles, refer to one of the following replacement procedures: Transfer Case Shift Control Switch Replacement in Transfer Case - NVG 246-NP8 Transfer Case Gear Indicator Switch Replacement in Transfer Case - NVG 261-NP2 Transfer Case Shift Control Switch Replacement in Transfer Case - NVG 263-NP1 Did you complete the replacement?	Go to Step 9	-
6	Test the 4WD Low signal circuit for a short to ground. Repair the circuit if necessary. Refer to Circuit Testing and Wiring Repairs .Did you find and correct the condition?	Go to Step 9	Go to Step 8
7	Test the 4WD Low signal circuit for an open. Repair the circuit if necessary. Refer to Circuit Testing and Wiring Repairs .Did you find and correct the condition?	Go to Step 9	Go to Step 8
8	Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?	Go to Step 9	-
9	Perform the following procedure in order to verify the repair: Select DTC. Select Clear Info. 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. Select Specific DTC. 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 - Vehicle	System OK