LEMON Manuals: Even more car manuals for everyone
Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 72 (Automatic Transmission Diagnosis - 4L80-E (Diesel)) >> Diagnostic Tests >> DTC P1811: Maximum Adapt & Long Shift >> 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. Perform the transmission fluid checking procedure. See appropriate AUTOMATIC article in TRANSMISSION SERVICING. Was the fluid checking procedure performed? If so, go to next step. If not, see appropriate AUTOMATIC article in TRANSMISSION SERVICING.
    3. NOTE: If any other engine or transmission DTCs are set, refer to their respective diagnostic tables first.
  3. Install a scan tool. Turn ignition on, engine off. Before clearing the DTC, use the scan tool to record the failure records. Using the CLEAR INFO function erases the failure records from the PCM. Record the DTC failure records. Clear the DTC. Select TFP SW. A/B/C on the scan tool. Start the engine and apply the brake pedal. Select each gear range. See TFP MANUAL VALVE POSITION SWITCH LOGIC  table under DESCRIPTION & OPERATION. Does each selected transmission range match the TFP SW. A/B/C display on the scan tool? If so, go to next step. If not, see DTC P1810: TFP MANUAL VALVE POSITION SWITCH ASSEMBLY - CIRCUIT MALFUNCTION  .
  4. Drive the vehicle in "D4" to obtain a 1-2, a 2-3, and a 3-4 shift time. Use the scan tool snapshot mode to record the shift times. Using the scan tool, review the shift time information for 1-2, 2-3, and 3-4 shift times. Were all of the shift times greater than the following:
    • 1-2 or 2-3 upshifts: 1.25 seconds
    • 3-4 upshifts: 6.37 seconds

    If so, go to next step. If not, go to step  8 .

  5. Perform the line pressure check procedure. See HYDRAULIC PRESSURE TESTS  under PERFORMANCE TESTS. Is the line pressure within specifications? If so, go to next step. If not, see SYMPTOM DIAGNOSIS  under TROUBLE SHOOTING.
  6. Remove the transmission oil pan. See appropriate AUTOMATIC article in TRANSMISSION SERVICING. Inspect the pan and the fluid for contamination. Is there excessive contamination in the transmission oil pan? If so, see appropriate OVERHAUL article. If not, go to next step.
  7. Inspect the transmission for fluid pressure loss in one of the following areas:
    • Valve Body Gasket
    • Forward Clutch Seals
    • Turbine Shaft Seals

    See appropriate OVERHAUL article. Did you find and correct the condition? If so, go to step  15 .

  8. Select the 1-2, 2-3, and the 3-4 Transmission Adaptive Pressure (TAP) cells on the scan tool. Were any of the upshift TAP cells greater than 16 psi (1.1 kg/cm2 )? If so, go to next step. If not, see DIAGNOSTIC AIDS  .
  9. Did the 3-4 shift time exceed 6.37 seconds? If so, go to step  12 . If not, go to next step.
  10. Did the 2-3 shift time exceed 1.25 seconds? If so, go to step  13 . If not, go to next step.
  11. Did the 1-2 shift time exceed 1.25 seconds? If so, go to step  14 .
  12. Inspect the following 3-4 shift circuit components:
    • 4th Gear Clutch Plates
    • 4th Gear Clutch Seals
    • Sticking 3-4 Shift Valve

    See appropriate OVERHAUL article. Did you find and correct the condition? If so, go to step  15 .

  13. Inspect the following 2-3 shift circuit components:
    • Turbine Shaft Seals
    • Forward Clutch Plates
    • Forward Clutch Seals
    • Direct Clutch Plates
    • Direct Clutch Seals
    • Center Support Seals
    • Improperly Tightened Center Support Bolt

    See appropriate OVERHAUL article. Did you find and correct the condition? If so, go to step  15 .

  14. Inspect the following 1-2 shift circuit components:
    • Low Roller Clutch
    • Intermediate Clutch Plates
    • Intermediate Clutch Seals
    • Intermediate Sprag Clutch
    • Overdrive Roller Clutch
    • Improperly Tightened Center Support Bolt

    See appropriate OVERHAUL article. Did you find and correct the condition? If so, go to next step.

    15. NOTE: CLEAR TAPS function will clear all adapt cells. This may affect transmission performance. The PCM will update the transmission adapt cell values as the vehicle is driven.
  15. Change the transmission fluid and filter. See appropriate AUTOMATIC article in TRANSMISSION SERVICING. Using the scan tool, perform the CLEAR TAPS function. Did you complete the procedure? If so, go to next step.
  16. Perform the following procedure to verify the repair:
    • Select DTC.
    • Select CLEAR INFO.
    • Place the gearshift lever in the "D4" position.
    • Drive the vehicle.
    • Operate the vehicle through several 1, 2, 3, 4 upshifts.
    • Review the scan tool 1-2, 2-3 and 3-4 shift times.

    Are the 1-2, 2-3, or 3-4 shift times less than the specified value?

    • 1-2 and 2-3 upshifts: 1.25 seconds
    • 3-4 upshifts: 6.37 seconds

    If so, system is okay. If not, go to step  1 .

scientia non olet · About LEMON Manuals