DTC P0740: TORQUE CONVERTER CLUTCH, NO RPM DROP AT LOCKUP
Circuit Description
Circuit is monitored continuously while ignition is on and gearshift lever is not in Park or Neutral. DTC sets if TCC does not achieve desired drop in RPM when TCC solenoid is near maximum duty cycle. A test failing 3 consecutive times is required to set DTC.
Possible Cause
- Misfire DTC set.
- Vehicle stalls (faulty TCC solenoid).
- TCC shaft seal/seal defective.
- Transmission fluid contaminated.
- TCC solenoid wiring harness defective.
- TCC defective.
- TCC hydraulic circuit damaged.
Diagnostic Procedure
1. Using scan tool, read DTCs. If good trip counter for DTC P0740 is not displayed or displayed count is not zero, go to step 10 . If good trip counter is displayed and displayed count is zero, go to next step.
2. If any listed DTCs are present, perform appropriate test(s). See TORQUE CONVERTER CLUTCH TESTS table. If no DTCs are present, go to next step.
3. Check transmission fluid for proper level and for any debris. Fill or repair transmission as necessary. If fluid level and condition are okay, go to next step.
4. Start engine. Using scan tool, perform TCC SYSTEM TEST. If vehicle does not stall, go to step 8 . If vehicle stalls, go to next step.
5. Using scan tool, perform GOV and 3-4 SHIFT VALVE SYSTEM TEST. Select 4th gear. If vehicle stalls, go to next step. If vehicle does not stall, go to step 7 .
6. Turn ignition off. Replace TCC solenoid. See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS. Using scan tool, perform GOV and 3-4 SHIFT VALVE SYSTEM TEST. Select 4th gear. If vehicle stalls, problem is internal. Check for blocked passage. If vehicle does not stall, testing is complete.
7. Turn ignition off. Remove oil pump and inspect reaction shaft, input shaft and input seal. Repair transmission as necessary. See appropriate OVERHAUL article. If transmission is okay, go to next step.
8. Turn ignition off. Connect a pressure gauge to transmission cooler OUT port. See appropriate SERVICING article in AUTOMATIC TRANSMISSIONS. Start engine. Using scan tool, perform TCC SYSTEM TEST. If pressure increases when TCC is actuated, go to next step. If pressure does not increase, repair leaks or blockage in hydraulic circuit, or repair valve body as necessary.
9. Turn engine off. Remove oil pump and inspect reaction shaft, input shaft and input seal. Repair transmission as necessary. See appropriate OVERHAUL article. If transmission is okay, there are no other potential causes remaining. TCC is assumed to be defective. Replace torque converter. See appropriate REMOVAL & INSTALLATION article in AUTOMATIC TRANSMISSIONS.
10. Conditions required to set DTC are not currently present. Inspect all applicable connectors and terminals for damage. Repair as necessary. If connectors and terminals are okay, see INACTIVE DTC CONDITION under SELF-DIAGNOSTIC SYSTEM. Testing is complete.