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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1508 (Automatic Transmission, 4L60-E/4L65-E Diagnosis (DTC P0218 To DTC P2761)) >> Diagnosis >> DTC P0748 >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 Chevrolet Corvette. 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 tests the ability of the PCM to command the PC solenoid valve.
  2. 3:  This step tests the PC solenoid valve and automatic transmission (AT) wiring harness assembly for incorrect resistance.
DTC P0748

Step Action Value(s) Yes No
1 Did you perform the Diagnostic System Check - Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls in Engine Controls
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 Failure Records. Using the Clear Info function erases the Failure Records from the PCM.
  3. Record the DTC Failure Records.
  4. Clear the DTC.
  5. Start the engine.
  6. Use the scan tool in order to command 0.1 amp through 1.0 amp while observing PC Sol. Ref. Current and PC Sol. Actual Current.
Is the PC Sol. Actual Current always within the specified value of the PC Sol. Ref. Current?		 0.16 amp Go to Intermittent Conditions in Engine Controls Go to Step 3 
3 
  1. Turn OFF the ignition.
  2. Disconnect the AT inline 20-way connector.
  3. Install the J 44152  Jumper Harness (20 pins) on the transmission side of the AT inline 20-way connector.
  4. Using the DMM and the J 35616  GM Terminal Test Kit, measure the resistance between terminals C and D of the J 44152  .

    Refer to Automatic Transmission Inline 20-Way Connector End View .

Does the resistance measure within the specified range?		 3-7 Ω Go to Step 5  Go to Step 4 
4 Does the resistance measure greater than the specified value? 7 Ω Go to Step 9  Go to Step 10 
5 Measure the resistance from terminal C of the J 44152  to the transmission case.
Refer to Automatic Transmission Inline 20-Way Connector End View .
Does the resistance measure greater than the specified value?		 250 K Ω Go to Step 6  Go to Step 11 
6
  1. Disconnect the J 44152  from the transmission side of the AT inline 20-way connector.
  2. Reconnect the transmission AT inline 20-way connector.
  3. Disconnect the PCM connector C2.
  4. Measure the resistance between PCM connector terminal C2-6 and terminal C2-8.
Does the resistance measure within the specified range?		 3-7 Ω Go to Step 8  Go to Step 7 
7 Does the resistance measure greater than the specified value? 7 Ω Go to Step 12  Go to Step 13 
8 Using the DMM and the J 35616  , measure the resistance from PCM connector terminal C2-6 to ground.
Does the resistance measure greater than the specified value?		 250 K Ω Go to Step 17  Go to Step 14 
9 Test the high control circuit and the low control circuit of the PC solenoid for an open between the AT inline 20-way connector and the PC solenoid.
Refer to Testing for Continuity in Wiring Systems.
Did you find an open condition?		 - Go to Step 16  Go to Step 15 
10 Test the high control circuit and the low control circuit of the PC solenoid for a shorted together condition between the AT inline 20-way connector and the PC solenoid.
Refer to Circuit Testing in Wiring Systems.
Did you find a shorted together condition?		 - Go to Step 16  Go to Step 15 
11 Test the high control circuit and 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 short to ground condition?		 - Go to Step 16  Go to Step 15 
12 Test the high control circuit and the low control circuit of the PC solenoid for an open between the PCM connector C2 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 18  -
13 Test the high control circuit and the low control circuit of the PC solenoid for a shorted together condition between the PCM connector C2 and the AT inline 20-way connector.
Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 18  -
14 Test the high control circuit and the low control circuit of the PC solenoid for a short to ground between the PCM connector C2 and the AT inline 20-way connector.
Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 18  -
15 Replace the PC solenoid valve.
Refer to Valve Body and Pressure Switch Replacement .
Did you complete the replacement?		 - Go to Step 18  -
16 Replace the AT wiring harness assembly.
Refer to Valve Body and Pressure Switch Replacement .
Did you complete the replacement?		 - Go to Step 18  -
17 Test the high control circuit and the low control circuit of the PC solenoid for a short to voltage.
Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 19  Go to Step 18 
18 Replace the PCM.
Refer to Powertrain Control Module (PCM) Replacement in Engine Controls.
Did you complete the replacement?		 - Go to Step 19  -
19 Perform the following procedure in order to verify the repair:
  1. Select DTC.
  2. Select Clear Info.
  3. Start the engine and ensure the following condition is met:

    The difference between the scan tool PC Sol. Actual Current and the PC Sol. Ref. Current is less than 0.16 amp.

  4. Select Specific DTC.
  5. Enter DTC P0748.

Has the test run and passed?		 - Go to Step 20  Go to Step 2 
20 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 in Engine Controls System OK
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