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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 52 (Automatic Transaxle Diagnosis - 4T65-E) >> Diagnostic Tests >> DTC P0748: Pressure Control Solenoid Electrical Problem >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Buick Regal, 2002 Buick Century, 2001 Buick Regal, and 2001 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the diagnostic system check? If so, go to next step. If not, see DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  2. Install a scan tool. Start the engine. Before clearing the DTCs, use the scan tool to record the failure records for reference. Using the CLEAR INFO function will erase the stored failure records from the PCM. Record the failure records. Clear the DTCs. With a scan tool, command several values of solenoid reference current from 0.1 amp through 1.1 amp and observe the scan tool display. Does the PC SOL. ACTUAL CURRENT reading differ from the PC SOL. REF. CURRENT reading by no more than 0.16 amp? If so, see DIAGNOSTIC AIDS  . If not, go to next step.
  3. Turn ignition off. Disconnect the transaxle in-line 20-way connector (additional DTCs may set). Connect the Jumper Harness (J 44152) to the transaxle side of the 20-way connector. Using the Connector Test Adapter Kit (J 35616-A), connect a DVOM from terminal "C" to terminal "D" of the jumper harness. Measure the resistance between terminals "C" and "D". Does the resistance measure within 3-7 ohms? If so, go to step  7 . If not, go to next step.
  4. Is the resistance greater than 7 ohms? If so, go to next step. If not, go to step  6 .
  5. Test the high control circuit (CKT 1228) of the PC solenoid valve for an open between the transaxle in-line 20-way connector and the PC solenoid valve. Test the low control circuit (CKT 1229) of the PC solenoid valve for an open between the transaxle in-line 20-way connector and the PC solenoid valve. Did you find the condition? If so, go to step  15 . If not, go to step  14 .
  6. Test the high control circuit (CKT 1228) and the low control circuit (CKT 1229) of the PC solenoid valve for a short together between the transaxle in-line 20-way connector and the PC solenoid valve. Did you find the condition? If so, go to step  15 . If not, go to step  14 .
  7. Test the high control circuit (CKT 1228) of the PC solenoid valve for a short to the transaxle case between the transaxle in-line 20-way connector and the PC solenoid valve. Test the high control circuit (CKT 1228) of the PC solenoid valve for a short to other power and ground circuits in the transaxle harness. Test from terminal "C" to all other terminals in the transaxle in-line 20-way connector. Did you find the condition? If so, go to step  15 . If not, go to next step.
  8. Test the low control circuit (CKT 1229) of the PC solenoid valve for a short to the transaxle case between the transaxle in-line 20-way connector and the PC solenoid valve. Test the low control circuit (CKT 1229) of the PC solenoid valve for a short to other power and ground circuits in the transaxle harness. Test from terminal "D" to all other terminals in the transaxle in-line 20-way connector. Did you find the condition? If so, go to step  15 . If not, go to next step.
  9. Disconnect the jumper harness from the transaxle side of the 20-way connector. Reconnect the 20-way connector. Disconnect the PCM connector C2. Using the DVOM, measure the resistance of the PC solenoid circuit between the PCM harness connector C2 terminals No. 45 and 46. Does the resistance measure within 3-7 ohms? If so, go to step  13 . If not, go to next step.
  10. Does the resistance measure greater than 7 ohms? If so, go to next step. If not, go to step  12 .
  11. Test the high control circuit (CKT 1228) of the PC solenoid valve for an open between the PCM and the transaxle in-line 20-way connector. Test the low control circuit (CKT 1229) of the PC solenoid valve for an open between the PCM and the transaxle in-line 20-way connector. Did you find and correct the condition? If so, go to step  17 .
  12. Test the high control circuit (CKT 1228) and the low control circuit (CKT 1229) of the PC solenoid valve for a short together between the PCM and the transaxle in-line 20-way connector. Did you find and correct the condition? If so, go to step  17 .
  13. Test the high control circuit (CKT 1228) of the PC solenoid valve for a short to ground or short to power between the PCM and the transaxle in-line 20-way connector. Test the low control circuit (CKT 1229) of the PC solenoid valve for a short to ground or short to power between the PCM and the transaxle in-line 20-way connector. Did you find and correct the condition? If so, go to step  17 . If not, go to step  16 .
  14. Replace the PC solenoid valve. See PRESSURE CONTROL SOLENOID VALVE  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  17 .
  15. Replace the transaxle internal wiring harness assembly. See TRANSAXLE INTERNAL WIRING HARNESS  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  17 .
  16. Replace the PCM. See POWERTRAIN CONTROL MODULE  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to next step.
  17. Perform the following procedure to verify the repair:
    • Select DTC.
    • Select CLEAR INFO.
    • Start the engine.
    • The PC solenoid valve actual current must be between 0.1 and 1.1 amp.
    • Select SPECIFIC DTC.
    • Enter DTC P0748.

    Has the test run and passed? If so, system is okay. If not, go to step  1 .

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