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Home >> GMC >> 2005 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 207 (Automatic Transmission - 5L40-E/5L50-E - (DTC P0115 To DTC P0756)) >> DTC P0748 >> Test Description

Test Description

WARNING: This page is about a different car, the 2005 Cadillac STS. 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. 2:  This step verifies the ability of the TCM to command the PC solenoid valve.
  2. 3:  This step verifies that the automatic transmission wiring harness and the PC solenoid have correct resistance.
DTC P0748

Step Action Value(s) Yes No
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2 
  1. Install a 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 ECM and the TCM Failure Records. Using the Clear Info function erases the Failure Records from the ECM and TCM.
    • Using the Clear Info function erases stored DTCs in both the ECM and TCM.
  3. Record the DTC Failure Records.
  4. Clear the DTC.
  5. Start the engine.
  6. Using the scan tool, increase and decrease the PC solenoid amperage.
  7. Observe the scan tool display.
Does the PC Sol. Actual Current vary from the PC Sol. Ref. Current by more than the specified amount?		 0.05 amps Go to Step 3  Go to Intermittent Conditions in Engine Controls - 3.6L or Intermittent Conditions in Engine Controls - 4.6L
3 
  1. Turn OFF the ignition.
  2. Disconnect the AT inline 20-way connector. Additional DTCs may set.
  3. Install the J 45681  jumper harness on the transmission side of the AT inline 20-way connector. See Special Tools .
  4. Using the DMM and the J 35616  GM terminal test kit, measure the resistance between the PC solenoid valve high control circuit and the PC solenoid valve low control circuit of the J 45681  . See Special Tools .

    Refer to Automatic Transmission Inline 20-Way Connector End View (5L40-E) or Automatic Transmission Inline 20-Way Connector End View (5L50-E) .

Is the resistance within the specified range?		 3.5-5.5 ohm Go to Step 7  Go to Step 4 
4 Is the resistance greater than the specified value? 5.5 ohm Go to Step 5  Go to Step 6 
5
  1. Test the high control circuit of the PC solenoid for an open between the AT inline 20-way connector and the PC solenoid valve.
  2. Test the low control circuit of the PC solenoid for an open between the AT inline 20-way connector and the PC solenoid valve.
Refer to Testing for Continuity in Wiring Systems.Did you find a condition?		 - Go to Step 18  Go to Step 19 
6 Test the high control circuit and the low control circuit of the PC solenoid for being shorted together between the AT inline 20-way connector and the PC solenoid.
Refer to Circuit Testing in Wiring Systems.
Did you find the condition?		 - Go to Step 18  Go to Step 19 
7 Measure the resistance from PC solenoid valve high control circuit of the jumper harness to ground.
Is the resistance less than the specified value?		 10 ohm Go to Step 8  Go to Step 9 
8
  1. Test the high control circuit of the PC solenoid for a short to ground between the AT inline 20-way connector and the PC solenoid.
  2. Test the low control circuit of the PC solenoid for a short to ground between the AT inline 20-way connector and the PC solenoid.
Refer to Testing for Short to Ground in Wiring Systems.Did you find a condition?		 - Go to Step 18  Go to Step 19 
9 Measure the resistance between the PC solenoid valve high control circuit and all other terminals, except the low control circuit, of the J 45681  . See Special Tools . Refer to Automatic Transmission Inline 20-Way Connector End View (5L40-E) or Automatic Transmission Inline 20-Way Connector End View (5L50-E) .
Is the resistance between the PC solenoid valve high control circuit and any other terminal, except the low control circuit, less than the specified value?		 100 ohm Go to Step 18  Go to Step 10 
10
  1. Disconnect the J 45681  from the transmission side of the AT inline 20-way connector. See Special Tools .
  2. Install the J 45681  on the TCM side of the AT inline 20-way connector. See Special Tools .
  3. Disconnect the TCM. Additional DTCs may set.
  4. Using the DMM and the J 35616  , measure the resistance from the PC solenoid valve low control circuit of the J 45681  to ground. See Special Tools .
Refer to Automatic Transmission Inline 20-Way Connector End View (5L40-E) or Automatic Transmission Inline 20-Way Connector End View (5L50-E) .Is the resistance less than the specified value?		 10 ohm Go to Step 11  Go to Step 12 
11 Test the low control circuit of the PC solenoid for a short to ground between the TCM connector and the AT inline 20-way connector.
Refer to Testing for Short to Ground andWiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 21  -
12 Using the DMM and the J 35616  , measure the resistance of the PC solenoid valve low control circuit between theJ 45681  and the TCM connector. See Special Tools . Refer to Automatic Transmission Inline 20-Way Connector End View (5L40-E) or Automatic Transmission Inline 20-Way Connector End View (5L50-E) .
Is the resistance less than the specified value?		 10 ohm Go to Step 14  Go to Step 13 
13 Test the low control circuit of the PC solenoid for an open between the TCM connector and the AT inline 20-way connector.
Refer to Testing for Continuity andWiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 21  -
14 Using the DMM and the J 35616  , measure the resistance from the PC solenoid valve high control circuit of the J 45681  to ground. See Special Tools .
Refer to Automatic Transmission Inline 20-Way Connector End View (5L40-E) or Automatic Transmission Inline 20-Way Connector End View (5L50-E) .
Is the resistance less than the specified value?		 10 ohm Go to Step 15  Go to Step 16 
15 Test the high control circuit of the PC solenoid for a short to ground between the TCM connector and the AT inline 20-way connector.
Refer to Testing for Short to Ground andWiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 21  -
16 Using the DMM and the J 35616  , measure the resistance of the PC solenoid valve high control circuit between theJ 45681  and the TCM connector. See Special Tools . Refer to Automatic Transmission Inline 20-Way Connector End View (5L40-E) or Automatic Transmission Inline 20-Way Connector End View (5L50-E) .
Is the resistance less than the specified value?		 10 ohm Go to Step 20  Go to Step 17 
17 Test the high control circuit of the PC solenoid for an open between the TCM connector and the AT inline 20-way connector. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 21  -
18 Replace the automatic transmission wiring harness. Refer to Transmission Internal Electrical Harness Replacement .
Is the action complete?		 - Go to Step 21  -
19 Replace the PC solenoid. Refer to Pressure Control Solenoid (PCS) Replacement .
Is the action complete?		 - Go to Step 21  -
20 Replace the TCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.
Is the action complete?		 - Go to Step 21  -
21 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:
    • Start and idle the engine.
    • System voltage must be at least 11 volts.
  4. Select Specific DTC.
  5. Enter DTC P0748.

Has the test run and passed?		 - Go to Step 22  Go to Step 2 
22 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 in Vehicle DTC Information System OK
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