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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1072 (Automatic Transmission - ALLISON, Diagnosis (DTC P0736 To DTC P0872)) >> Diagnosis >> DTC P0872 >> Test Description

Test Description

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

  1. 5:  This step tests the TCM response function.
  2. 7:  This step tests the transmission wiring harness integrity.
  3. 8:  This step tests and evaluates the internal wiring harness and inspects the PSM for a failed condition.
  4. 14:  This step tests the engine wiring harness integrity.
DTC P0872

Step Action Value Yes No
Schematic Reference: Automatic Transmission Controls Schematics
1 Did you perform the Diagnostic System Check - Automatic Transmission? - Go to Step 2  Go to Diagnostic System Check - Automatic Transmission
2 Measure the transmission fluid level. Refer to Transmission Fluid Checking Procedure .
Is the transmission fluid level correct?		 - Go to Step 3  Go to Transmission Fluid Checking Procedure
3 Measure line pressure. Refer to Line Pressure Check Procedure .
Is the pressure within the specified value?		 - Go to Step 4  Go to Symptoms - Automatic Transmission
4
  1. Install the scan tool.
    2. 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.
  2. Record the DTC Freeze Frame and Failure Records.
  3. Clear the DTC.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and Failure Records.
Is DTC P0872 currently active?		 - Go to Step 5  Go to Diagnostic Aids
5 
  1. Turn the ignition OFF.
  2. Disconnect the C2 connector (RED) from the TCM.
  3. Install the J 39700  breakout box and the J 43799  breakout box adapter at C2 connector.
  4. Connect C2 connector terminal 3 to a known good ground.
  5. Turn ON the ignition, with the engine OFF.
Does the scan tool indicate TFP SW. E status is ON when grounded and OFF when open?		 - Go to Step 6  Go to Step 15 
6
  1. Turn the ignition OFF.
  2. Connect the C2 connector (RED) to the TCM.
  3. Disconnect the transmission 20-way connector. Additional DTCs may set.
  4. Turn ON the ignition, with the engine OFF.
  5. Connect terminal E at the transmission 20-way connector to a known good ground.
Does the scan tool indicate TFP SW. E status is ON when grounded and OFF when open?		 - Go to Step 7  Go to Step 14 
7 
  1. Connect the transmission 20-way connector.
  2. Remove the oil pan. Refer to Oil Pan Replacement .
  3. Disconnect the AT internal wiring harness from the PSM and ground terminal C.
Does the scan tool indicate TFP SW. E status is ON when grounded and OFF when open?		 - Go to Step 8  Go to Step 13 
8 
  1. Remove the PSM from the control valve body and leave the AT internal harness connected. Refer to Pressure Switch Manifold Replacement .
  2. Provide a ground connection for the PSM to either the control valve body or the transmission main case.
  3. Using the eraser end of a pencil, push gently on the pressure switch E membrane.
Does the scan tool indicate TFP SW. E status is ON when grounded and OFF when open?		 - Go to Step 9  Go to Step 12 
9 Remove the control valve body and inspect for a stuck or sticking E shift valve. Refer to Control Valve Body Disassemble .
Was the E shift valve stuck or sticking?		 - Go to Step 11  Go to Step 10 
10 Replace the E shift solenoid and install the control valve body. Refer to Control Valve Body Replacement .
Did you complete the replacement and installation of the valve body?		 - Go to Step 16  -
11 Clean and/or polish the sticking valve to restore free movement or replace the control valve body assembly. Refer to Control Valve Body Replacement .
Did you restore free movement or replace the valve body assembly?		 - Go to Step 16  -
12 Replace the PSM. Refer to Pressure Switch Manifold Replacement .
Did you complete the replacement?		 - Go to Step 16  -
13 Replace the AT internal wiring harness. Refer to Wiring Harness Replacement .
Did you complete the replacement?		 - Go to Step 16  -
14  Inspect the engine wiring harness circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 16  Go to Diagnostic Aids
15
IMPORTANT: In most cases, the TCM is not at fault. Investigate thoroughly before replacing the TCM.
Replace the TCM. Refer to Transmission Control Module (TCM) Replacement .Did you complete the replacement?		 - Go to Step 16  -
16 Perform the following procedure in order to verify the repair:
  1. Clear the DTC.
  2. Start the engine and idle at normal operating temperature.
  3. Apply the brake pedal.
  4. Select Specific DTC.
  5. Enter DTC P0872.
  6. Select each transmission range, P, R, N, D, D3, D2 and D1.

Has the test run and passed?		 - System OK Go to Step 1 
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