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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 P0756: 2-3 Shift Solenoid Valve - Performance >> 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 freeze frame and failure records. Using the CLEAR INFO function erases the freeze frame and failure records from the PCM. Record the freeze frame and failure records. Clear the DTCs. Select TFP SWITCH A/B/C on the scan tool. With the engine running, apply the brake pedal and select each transmission range. See TFP MANUAL VALVE POSITION SWITCH LOGIC  table under DESCRIPTION & OPERATION. Does each selected transmission range match the scan tool TFP SWITCH A/B/C display? If so, go to next step. If not, see DTC P1810: TFP MANUAL VALVE POSITION SWITCH ASSEMBLY - CIRCUIT MALFUNCTION .
  3. Raise and support the drive axle assembly. Start the engine. With the transmission in the D4 range, use the scan tool to command 1st, 2nd, 3rd, and 4th gears while accelerating the vehicle. Was 1st gear commanded and not achieved, or 4th gear commanded and another gear occurred? If so, go to next step. If not, see DIAGNOSTIC AIDS .
  4. Inspect the shift solenoid/hydraulic circuits for an internal malfunction at one or both of the shift solenoids. Inspect the shift solenoid/hydraulic circuits for damaged seals on one or both of the shift solenoids. Did you find and correct the condition? If so, go to next step.
  5. Perform the following procedure to verify the repair:
    • Select DTC.
    • Select CLEAR INFO.
    • Operate the vehicle.
    • The PCM must see the proper gear ratio for each gear for greater than one second in D1, D2, D3, and D4.
    • Accelerate the vehicle with the throttle angle greater than 8 percent up to 55 MPH.
    • Select SPECIFIC DTC.
    • Enter DTC P0756.

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

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