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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 102 (Automatic Transmission Diagnosis - 4L60-E) >> Diagnostic Tests >> DTC P1870: Transmission Component Slipping >> Diagnostic Procedure

Diagnostic Procedure

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  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. Check transmission fluid level. Fill if necessary. See appropriate AUTOMATIC article in TRANSMISSION SERVICING. Go to next step.
  3. Connect scan tool to DLC. Turn ignition on, engine off. Using scan tool, record freeze frame and failure records for reference, and then clear DTCs. Test drive vehicle in 4th gear with TCC commanded on. Using scan tool, monitor TCC slip speed. If TCC slip speed is 80-800 RPM for 7 seconds, go to next step. If TCC slip speed is not 80-800 RPM for 7 seconds, see DIAGNOSTIC AIDS .
  4. Check TCC solenoid valve for internal malfunction or damaged seals. Repair as necessary. After repairs, go to step  14. If TCC solenoid valve is okay, go to next step.
  5. Check all shift solenoid valves for internal malfunctions or damaged seals. Repair as necessary. After repairs, go to step  14. If shift solenoids are okay, go to next step.
  6. Check valve body for stuck regulator apply valve or scored regulator apply valve body. Repair as necessary. After repairs, go to step  13. If no problem is found, go to next step.
  7. Check torque converter for worn stator shaft bushing, defective stator roller clutch or external damage and leaks. Repair as necessary. After repairs, go to step  13. If torque converter is okay, go to next step.
  8. Check oil pump assembly for stuck, mispositioned or incorrectly installed valves and springs. Check for mispositioned oil pump gasket, restricted or damaged orifice cup plugs. Check for overtightened or unevenly tightened pump body-to-cover bolts. Repair as necessary. After repairs, go to step  13. If no problem is found, go to next step.
  9. Check input housing and shaft assembly for restricted or damaged turbine shaft retainer and ball assembly. Check for cut or damaged turbine shaft "O" ring seal. Repair as necessary. After repairs, go to step  13. If no problem is found, go to next step.
  10. Check condition of 2-4 band components (i.e., pistons, seals, band, oil passages, case piston bore, etc.). Repair as necessary. After repairs, go to step  13. If no problem is found, go to next step.
  11. Check condition of forward clutch components (i.e., clutch plates, piston, seals, retainer and ball, etc.). Repair as necessary. After repairs, go to step  13. If no problem is found, go to next step.
  12. Check condition of 3-4 clutch components (i.e., clutch plates, piston, seals, orifice cup plug, etc.). Repair as necessary. After repairs, go to next step. If no problem is found, see DIAGNOSTIC AIDS .
  13. Change transmission fluid. See appropriate AUTOMATIC article in TRANSMISSION SERVICING. Using scan tool, clear TAPS function. After repairs, go to next step.
  14. Using scan tool, clear DTCs. Test drive vehicle in "D4" range with TCC on and TP sensor angle at 20-99 percent. Ensure TCC slip speed -20 to 60 RPM for at least 7 seconds. Check for DTCs. If DTC P1870 does not return, system is okay. If DTC P1870 returns, go to step  1.
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