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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 59 (Automatic Transmission Diagnosis - 4L80-E) >> Diagnostic Tests >> DTC P0748: Pc Solenoid Circuit - Electrical Malfunction >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 GMC Yukon XL, 2002 GMC Sierra, 2002 Chevrolet Suburban, and 2002 Chevrolet Silverado. 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. Turn ignition on, engine off. Before clearing the DTCs, use the scan tool to record the failure records. Using the CLEAR INFO function erases the failure records from the PCM. Record the failure records. Clear the DTCs. With the transmission in Park, start the engine. Using the transmission output control function on the scan tool, apply 0.1-1.0 amps while observing the PC REF. CURRENT and the PC ACT. CURRENT. Is the PC ACT. CURRENT reading always within 0.16 amp of the PC REF. CURRENT? If so, see DIAGNOSTIC AIDS . If not, go to next step.
  3. Turn ignition off. Disconnect the transmission in-line 20-way harness connector. Additional DTCs will set. Install the Jumper Harness (J-44152) on the transmission side of the 20-way connector. Using a DVOM and the Connector Test Adapter Kit (J-35616-A), measure the resistance between terminals "C" and "D". Does the resistance measure 3-7 ohms? If so, go to step  5. If not, go to next step.
  4. Disconnect the transmission wiring harness at the PC solenoid valve. Measure the resistance of the PC solenoid valve. Does the resistance measure 3-7 ohms? If so, go to step  15. If not, go to step  7.
  5. Measure the resistance from terminal "C" on the jumper harness to the transmission case. Does the resistance measure less than 7 ohms? If so, go to next step. If not, go to step  8.
  6. Inspect the transmission wiring harness assembly for a short to ground. Was a shorted condition found? If so, go to step  15. If not, go to next step.
  7. Replace the PC solenoid valve. See SOLENOID VALVES  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  17.
  8. Measure the resistance between terminal "C" and all other terminals, except terminal "D", of the jumper harness. Is the resistance between terminal "C" and any other terminal, except terminal "D", less than 100 ohms? If so, go to step  15. If not, go to next step.
  9. Disconnect the jumper harness from the transmission side of the in-line 20-way harness connector. Reconnect the transmission in-line 20-way harness connector. Disconnect the PCM harness connector C2. Measure the resistance between PCM harness connector C2 terminals No. 6 and 8. Does the resistance measure 3-7 ohms? If so, go to next step. If not, go to step  11.
  10. Connect the DVOM to PCM harness connector C2 terminal No. 6 and to a good ground. Measure the resistance. Does the resistance measure greater than 7 ohms? If so, go to step  16. If not, go to step  14.
  11. Does the resistance in step  9 measure greater than 7 ohms? If so, go to next step. If not, go to step  13.
  12. Test the PC solenoid valve high control circuit (1228) for an open. Test the PC solenoid valve low control circuit (1229) for an open. Repair the circuits if necessary. Did you find and correct the condition? If so, go to step  17.
  13. Test the PC solenoid valve high control circuit (1228) and the PC solenoid valve low control circuit (1229) for a shorted together condition. Did you find and correct the condition? If so, go to step  17.
  14. Test the PC solenoid valve high control circuit (1228) for a short to ground. Test the PC solenoid valve low control circuit (1229) for a short to ground. Repair the circuits if necessary. Did you find and correct the condition? If so, go to step  17.
  15. Replace the transmission internal wiring harness assembly. See TRANSMISSION 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.
    • The engine is running.
    • The PC solenoid duty cycle is 2-95 percent.
    • 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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