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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 146 (Automatic Transmission - 4L60-E/4L65-E/4L70-E - DTC P0973 To DTC P2771) >> DTC P2771 >> Test Description

Test Description

WARNING: This page is about a different car, the 2007 GMC Yukon XL, 2007 GMC Yukon, 2007 Chevrolet Tahoe, 2007 Chevrolet Suburban, and 2007 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 4WD low signal circuit.
  2. 4:  This step tests for an open in the 4WD low signal circuit or a faulty transfer case control module.
DTC P2771

Step Action Values Yes No
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2
  1. Install a scan tool.
  2. Start the engine, parking brake disengaged.
    3. IMPORTANT: Before clearing the DTC, 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 DTC Freeze Frame and Failure Records.
  4. Clear the DTC.
  5. Place the transmission in NEUTRAL.
  6. Select 4HI on the transfer case selector.
    7. IMPORTANT: It may be necessary to drive the vehicle slightly forward to engage 4LO on the transfer case.
  7. Select 4LO on the transfer case selector.
Does the scan tool 4WD Low display Disabled when you select 4HI, then Enabled when you select 4LO?		 - Go to Testing for Intermittent Conditions and Poor Connections Go to Step 3 
3 
  1. Turn OFF the ignition.
  2. Disconnect the transfer case control module connector.
  3. Turn ON the ignition, with the engine OFF.
Does the scan tool 4WD Low indicate Enabled?		 - Go to Step 6  Go to Step 4 
4 
  1. Connect a fused jumper between the harness side of the 4WD low signal circuit and ground at the transfer case control module connector.
  2. Observe the scan tool 4WD Low parameter.
Does the scan tool 4WD Low parameter indicate Enabled when the 4WD low signal circuit, is grounded?		 - Go to Step 5  Go to Step 7 
5 Replace the transfer case control module.
Refer to Control Module References for replacement, setup and programming.
Did you complete the replacement?		 - Go to Step 9  -
6 Test the 4WD low signal circuit for a short to ground.
Refer to Testing for Short to Ground 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.
Refer to Testing for Continuity and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 9  Go to Step 8 
8 Replace the ECM.
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:
  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions:
    1. Select 4LO on the transfer case selector.
    2. Drive the vehicle in D4.
    3. Verify that the speed ratio is 2.5-2.9 for 1.5 seconds.
    4. Select 2HI or 4HI on the transfer case selector.
    5. Drive the vehicle in D4 with the TCC ON.
    6. Verify that the speed ratio is 0.8-1.2 for 5 seconds.
  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 - Vehicle System OK
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