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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 32 (AUTOMATIC TRANSMISSION - ALLISON - DIAGNOSTICS (DTCs P0732-P0877)) >> DTC P0826 >> Test Description

Test Description

WARNING: This page is about a different variant/trim than selected.

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

  1. 3:  This step tests signal voltage to the TCM.
  2. 4:  This step tests supply voltage to the driver shift request switch.
  3. 5:  This step tests resistance of the driver shift request switch.
DTC P0826

Step Action Value Yes No
Schematic Reference: Automatic Transmission Controls Schematics
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2
  1. Install the scan tool.
  2. Turn ON the ignition, with the engine OFF.
    3. IMPORTANT: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data.
  3. Record the DTC Freeze Frame and Failure Records.
  4. Clear the DTC.
  5. Using the scan tool, measure ignition voltage.
Is the voltage within the specified range?		 9-18 V Go to Step 3  Go to DTC P0562 for low voltage or DTC P0563 for high voltage
3
  1. Turn the ignition OFF.
  2. Disconnect the 80-way connector at the TCM.
  3. Install the J 39700  breakout box, the J-47275  breakout box adapter and the J 47275-1 magnetic overlay. See Special Tools .
  4. Turn ON the ignition, with the engine OFF.
  5. Using the DMM, measure voltage at terminal 56 and a known good ground.
  6. Operate the driver shift request switch in the TAP up and TAP down position.
Is the voltage within the specified value?		 2.5 V Go to Diagnostic Aids  Go to Step 4 
4
  1. Turn the ignition OFF.
  2. Disconnect terminals 20 and 21 at the driver shift request switch.
  3. Using the J 35616  GM terminal test kit, connect the DMM to terminal 21 and a known good ground.
  4. Turn ON the ignition, with the engine OFF.
Is the voltage within the specified range?		 11.75-12.75 V Go to Step 5  Go to Step 6 
5
  1. Turn the ignition OFF.
  2. Using the J 35616  , connect the DMM to terminals 20 and 21 of the driver shift request switch.
  3. Operate the driver shift request switch in the Tap up and Tap down position.
Is the resistance within the specified value?		 OFF: 6.84 K ohm
Tap up: 1.87 K ohm
Tap down: 3.97 K ohm		 Go to Step 7  Go to Step 9 
6
IMPORTANT: The condition that affects this circuit may exist in other connecting branches of the circuit. Refer to Power Distribution Schematics for complete circuit distribution.
  1. Inspect the ignition 0 voltage circuit for an open. Refer to Circuit Protection - Fuses .
  2. Replace the fuse if necessary.
Was the fuse open?		 - Go to Step 11  Go to Step 8 
7 Test the signal circuit of the AT driver shift request switch for an open between the AT driver shift request switch and the TCM. Refer to Testing for Continuity and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 11  Go to Step 10 
8 Test the ignition 0 voltage circuit of the AT driver shift request switch for an open between the fuse block and the AT driver shift request switch. Refer to Testing for Continuity and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 11  -
9 Replace the AT driver shift request switch. Refer to Shift Lever Replacement (With Tow/Haul Switch) .
Did you complete the replacement?		 - Go to Step 11  -
10
IMPORTANT: In most cases, the TCM is not at fault. Investigate thoroughly before replacing the TCM.
Replace the TCM. Refer to Control Module References for replacement, setup, and programming.Did you complete the replacement?		 - Go to Step 11  -
11 Perform the following procedure in order to verify the repair:
  1. Clear the DTC.
  2. Operate the vehicle while using the driver shift request switch.
  3. Select Specific DTC.
  4. Enter DTC P0826.

Has the test run and passed?		 - Go to Step 12  Go to Step 2 
12 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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