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Home >> Saturn >> 2000 >> LS Automatic >> Repair and Diagnosis (Single Page) >> Transmission >> Automatic Trans >> Automatic Transaxle Diagnosis - 4T40-E & 4T45-E >> Diagnostic Tests >> DTC P0742: TCC Circuit Inoperative (Stuck On) >> Diagnostic Procedure

Diagnostic Procedure

NOTE: For connector end views and component locations, see Figure -Figure . For circuit locations, see WIRING DIAGRAMS  .
  1. Perform OBD system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  under DIAGNOSIS & TESTING. After performing OBD system check, go to next step.
  2. Connect scan tool to DLC. Turn ignition switch to ON position. Using scan tool, record freeze frame and failure records for reference. Clear DTC. Using scan tool, observe TCC release pressure. If TCC release pressure is indicated on scan tool, see DIAGNOSTIC AIDS  . If TCC release pressure is not indicated on scan tool, go to next step.
  3. Start engine. If scan tool indicates TCC release pressure is indicated, go to step  8 . If TCC release pressure is not indicated, go to next step.
  4. Turn ignition off. Disconnect transaxle 20-pin connector. Turn ignition switch to ON position. Using scan tool, observe TCC release pressure. If TCC release pressure is indicated on scan tool, go to step  6 . If TCC release pressure is not indicated on scan tool, go to next step.
  5. Check for short to ground in TCC release switch signal circuit between appropriate PCM connector and transaxle 20-pin connector. Repair as necessary. After repairs, go to step  12 . If TCC release switch signal circuit is okay, go to step  11 .
  6. Check for short to ground in TCC release switch signal circuit between transaxle 20-pin connector and TFP manual valve position switch. If short to ground is found in TCC release switch signal circuit, go to step  10 . If TCC release switch signal circuit is okay, go to next step.
  7. Remove TFP manual valve position switch. Inspect TCC release switch for damaged or leaking seal, sediment or debris in switch, damaged and stuck switch contacts. If fault is found with TFP manual valve position switch, go to step  9 . If TFP manual valve position switch is okay, go to next step.
  8. Inspect TCC PWM hydraulic circuit. Check for plugged TCC PWM solenoid exhaust, TCC regulator apply valve or control valve stuck in apply position, TCC feed limit valve stuck, causing no or low TCC feed limit pressure and release pressure or stuck pressure regulator valve. See HYDRA-MATIC 4T40-E & 4T45-E OVERHAUL article. Repair or replace component as necessary. After repairs, go to step  12 .
  9. Replace TFP manual valve position switch. See HYDRA-MATIC 4T40-E & 4T45-E OVERHAUL article. After repairs, go to step  12 .
  10. Replace internal transaxle wire harness. See HYDRA-MATIC 4T40-E & 4T45-E OVERHAUL article. After repairs, go to step  12 .
  11. Replace PCM. After replacement, program PCM. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION. After repairs, go to next step.
  12. After repair is complete, select DTC on scan tool. Select CLEAR INFO function. Select SPECIFIC DTC and enter DTC "P0742". Drive vehicle in "D" position with throttle position angle at 12-75 percent. TCC release fluid must be present at TCC release switch (switch open) for 6 seconds. If DTC P0742 is not present, repair is complete. If DTC P0742 is still present, repeat test.
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