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Home >> GMC >> 2006 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 29 (AUTOMATIC TRANSMISSION - ALLISON - DIAGNOSTICS (DTCs P0218-P0731)) >> DTC P0703 >> 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. 2:  This step tests brake switch status.
  2. 3:  This step tests for voltage at the TCM.
  3. 4:  This step tests for voltage before the stop lamp switch.
  4. 5:  This step tests for voltage after the stop lamp switch.
DTC P0703

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. CAUTION: When performing service on or near the SIR components or the SIR wiring, the SIR system must be disabled. Refer to SIR Disabling and Enabling Zones. Failure to observe the correct procedure could cause deployment of the SIR components, personal injury, or unnecessary SIR system repairs.
  5. Apply and release the service brake.
Does the scan tool indicate that the brake switch is toggling off and on?		 - Go to Diagnostic Aids Go to Step 3 
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.
  5. Using the DMM, measure voltage at connector terminal 2 and ground.
  6. Apply and release the service brake.
Is voltage within the specified value?		 Brakes applied: 0.0 V
Brakes released: 12.0 V		 Go to Diagnostic Aids Go to Step 4 
4 Using the DMM, measure voltage at terminal C of the stop lamp switch and ground. Refer to Automatic Transmission Controls Schematics .
Is voltage within the specified value?		 B+ Go to Step 5  Go to Step 6 
5 Using the DMM, measure voltage at terminal D of the stop lamp switch.
Is voltage available?		 B+ Go to Step 8  Go to Step 7 
6
  1. Remove the brake fuse.
  2. Inspect the brake fuse for an open. Refer to General Electrical Diagnosis Procedures .
Did you find and correct the condition?		 - Go to Step 9  -
7 Repair or replace the stop lamp switch. Refer to Stop Lamp Switch Replacement .
Did you complete the repair or replacement?		 - Go to Step 9  -
8 Inspect the engine wiring harness for an open or short to ground. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 9  -
9 Perform the following procedure in order to verify the repair:
  1. Clear the DTC.
  2. Using the scan tool, monitor the brake switch.
  3. Operate the vehicle under the Conditions for Setting the DTC.
  4. Select Specific DTC.
  5. Enter DTC P0703.

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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