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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 55 (Automatic Transaxle Diagnosis - 4T65-E) >> Diagnostic Tests >> DTC P0751: 1-2 Shift Solenoid Performance >> 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. Did you perform the transmission fluid checking procedure? If so, go to next step. If not, perform the transmission fluid checking procedure. See appropriate AUTOMATIC article in TRANSMISSION SERVICING.
    3. CAUTION: DO NOT drive the vehicle for an extended period of time because additional internal damage may occur.
  3. 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 for reference. Using the CLEAR INFO function will erase the stored freeze frame and failure records from the PCM. Record the freeze frame and failure records. Clear the DTCs. Accelerate the vehicle in D4 range. With the scan tool, observe current (commanded) gear and gear ratio for each gear. Standard values are:
    • 1st: 2.87:1 to 2.97:1
    • 2nd: 1.52:1 to 1.62:1
    • 3rd: 0.95:1 to 1.05:1
    • 4th: 0.65:1 to 0.75:1

    Did the gear ratios indicate a 2-2-3-3 shift pattern? If so, go to next step. If not, see DIAGNOSTIC AIDS  .

  4. Inspect the 1-2 shift solenoid valve/hydraulic circuit for the following conditions:
    • An internal malfunction.
    • Damaged seals on the shift solenoid valve.

    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.
    • Drive the vehicle in D4 with the throttle angle at least 10 percent until the transaxle shifts to 4th gear.
    • Ensure that the gear ratios are as specified for 1st and 4th gear.
    • Select SPECIFIC DTC.
    • Enter DTC P0751.

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

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