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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 30 (AUTOMATIC TRANSMISSION - ALLISON - DIAGNOSTICS (DTCs P0218-P0731)) >> DTC P0708 >> Test Description

Test Description

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

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

  1. 4:  This step tests TCM input response.
  2. 5:  This step tests the integrity of the engine wiring harness.
  3. 6:  This step tests the integrity of the transmission internal wiring harness.
DTC P0708

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 Inspect the shift linkage for proper adjustment. Refer to Automatic Transmission Range Selector Cable Adjustment .
Is the shift linkage properly adjusted?		 - Go to Step 3  -
3
  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. With the scan tool, monitor IMS A/B/C/P status while moving the shift selector through each range. Refer to Transmission Internal Mode Switch Logic .
Does each selected transmission range match the scan tool IMS display?		 - Go to Diagnostic Aids Go to Step 4 
4
  1. Turn the ignition OFF.
  2. Install the J 39700  breakout box, the J-47275  breakout box adapter and the J 47275-1 magnetic overlay at the TCM. See Special Tools .
  3. Disconnect the 16-way bypass connector on the J-47275  . See Special Tools .
  4. Turn ON the ignition, with the engine OFF.
  5. In sequence, connect terminal 58 to terminals 14, 34, 53 and 73 to ground.
  6. Using the scan tool, monitor IMS A/B/C/P status.
Does each IMS signal indicate LOW when grounded and HIGH when open?		 A = terminal 73
B = terminal 53
C = terminal 14
P = terminal 34
HIGH = Open
LOW = Grounded		 Go to Step 5  Go to Step 10 
5
  1. Turn the ignition OFF.
  2. Connect the 80-way connector to the TCM.
  3. Disconnect the transmission AT inline 20-way connector. Additional DTCs may set.
  4. Install the J 44152  jumper harness (20 pins) on the engine side of the AT inline 20-way connector.
  5. Turn ON the ignition, with the engine OFF.
  6. Using the J 35616  GM terminal test kit, connect a fused jumper wire, in sequence, to terminals T, U, V and W to ground. Refer to Automatic Transmission Inline Harness Connector End View .
Does each IMS signal indicate LOW when grounded and HIGH when open?		 - Go to Step 6  Go to Step 7 
6
  1. Turn the ignition OFF.
  2. Connect the transmission AT inline 20-way connector.
  3. Remove the transmission oil pan. Refer to Oil Pan Replacement .
  4. Remove the AT internal wiring harness at the IMS connector.
  5. Turn ON the ignition, with the engine OFF.
  6. Using the J 35616  , connect a fused jumper wire, in sequence, to terminals B, D, C and E to ground.
Does each IMS signal indicate LOW when grounded and HIGH when open?		 - Go to Step 9  Go to Step 8 
7 Test the IMS circuit between the TCM and AT inline 20-way connector for an open or short to ground condition. Refer to Circuit Testing .
Did you find and correct the condition?		 - Go to Step 11  -
8 Replace the internal wiring harness. Refer to Wiring Harness Replacement .
Did you complete the replacement?		 - Go to Step 11  -
9 Replace the internal mode switch. Refer to Transmission Internal Mode Switch Replacement .
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. Using the scan tool, monitor the IMS A/B/C/P status while moving the shift selector through each range.
  3. Select Specific DTC.
  4. Enter DTC P0708.

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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