LEMON Manuals: Even more car manuals for everyone
Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 69 (Automatic Transmission Diagnosis - 4L80-E (Diesel)) >> Diagnostic Tests >> DTC P0748: Pc Solenoid Circuit - Electrical Malfunction >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 GMC Cab & Chassis Sierra and 2002 Chevrolet Cab & Chassis 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 in-line 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  6 . If not, go to next step.
  4. Disconnect the 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 next step. If not, go to step  8 .
  5. 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 .
  6. Measure the resistance from jumper harness terminal "C" to the transmission case. Does the resistance measure less than 250 k/ohms? If so, go to next step. If not, go to step  9 .
  7. Test the PC solenoid valve high control (1228) and low control (1229) circuits for a short to ground between the PC solenoid connector and the transmission in-line 20-way connector. Replace the harness if necessary. Did you find and correct the condition? If so, go to step  17 . If not, go to next step.
  8. Replace the PC solenoid valve. See SOLENOID VALVES  under REMOVAL & INSTALLATION. Did you complete the replacement? If so, go to step  17 .
  9. Disconnect the jumper harness from the transmission side of the transmission in-line 20-way connector. Install the jumper harness on the engine side of the transmission in-line 20-way connector. Turn ignition on, engine off. Test the PC solenoid valve high control circuit (1228) for a short to power. Test the PC solenoid valve low control circuit (1229) for a short to power. Did you find and correct the condition? If so, go to step  17 . If not, go to next step.
  10. Turn ignition off. Reconnect the transmission in-line 20-way connector. Disconnect the PCM connector C1. Measure the resistance between PCM connector C1 terminals C7 and C15. Does the resistance measure 3-7 ohms? If so, go to next step. If not, go to step  12 .
  11. Measure the resistance between PCM connector C1 terminal C7 and a good ground. Does the resistance measure greater than 250 k/ohms? If so, go to step  16 . If not, go to step  15 .
  12. Does the resistance in step  10 measure greater than 7 ohms? If so, go to next step. If not, go to step  14 .
  13. Test the PC solenoid valve high control circuit (1228) and low control circuit (1229) for an open between the PCM and the transmission in-line 20-way connector. Did you find and correct the condition? If so, go to step  17 .
  14. Test the PC solenoid valve high control circuit (1228) and low control circuit (1229) for a short together between the PCM and the transmission in-line 20-way connector. Did you find and correct the condition? If so, go to step  17 .
  15. Test the PC solenoid valve high control circuit (1228) and low control circuit (1229) for a short to ground between the PCM and the transmission in-line 20-way connector. Did you find and correct the condition? 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 .

scientia non olet · About LEMON Manuals