DTC P1740: TORQUE CONVERTER CLUTCH OR OVERDRIVE SOLENOID PERFORMANCE
Circuit Description
TCC and overdrive clutch are tested when PCM requests TCC engagement in 3rd gear and Overdrive. DTC will set if expected RPM drop is not achieved while attempting to engage TCC and/or Overdrive. DTC indicates malfunctioning torque converter or overdrive clutch.
Possible Cause
The following items may be area of concern:
- Fluid level or quality problem.
- Transmission wiring and connector defective.
- Transmission mechanically defective.
- Low fuel level.
- Transmission temperature below 32°F (0°C).
- Transfer case is in Low range.
- Engine RPM DTCs set.
- Misfire DTCs set (P0300-P0306).
- Output speed sensor DTC is set.
- PTO is engaged.
- TP sensor DTCs set (P0121-P0123).
- Torque converter defective.
Diagnostic Procedure
1. Using scan tool, read DTCs. If good trip counter for DTC P1740 is not displayed or displayed count is not zero, go to step 17 . If good trip counter is displayed and displayed count is zero, go to next step.
2. If any DTCs listed are present, perform appropriate diagnostic test(s). See TCC OR OD SOLENOID TESTS table. If no DTCs are present, go to next step.
3. Ensure fuel tank is at least 1/4 full. If fuel level is too low, correct fuel level and retest. If fuel level is okay, go to next step.
4. Ensure transfer case is not in Low range, PTO is not engaged and transmission fluid temperature is greater than 32°F (0°C). Go to next step.
5. Turn ignition on. Using scan tool, build a custom display with engine RPM, output shaft speed, TCC solenoid, OD solenoid and throttle position. Set OD OFF switch to OFF position. Test drive vehicle and maintain 55 MPH with a minimum throttle opening voltage of 1.15 volts for 20 seconds. Note shift patterns while vehicle is attaining speed. If engine RPM is within 60 RPM of output shaft speed RPM, go to next step. If engine RPM is not within 60 RPM of output shaft speed RPM, go to step 12 .
6. If output shaft speed RPM is greater than engine RPM, go to next step. If output shaft speed RPM is equal to or less than engine RPM, go to step 12 .
7. Test drive vehicle and maintain 55 MPH. Engage overdrive. If engine RPM is 69 percent of output shaft speed, go to step 12 . If engine RPM is not 69 percent of output shaft speed, go to next step.
8. Connect a 0-300 psi (0-21 kg/cm2 ) pressure gauge to transmission OD clutch pressure test port. Connect a second 0-300 psi (0-21 kg/cm2 ) pressure gauge to transmission governor pressure test port. See HYDRAULIC PRESSURE TESTS . Ensure engine and transmission are at normal operating temperature. With an assistant, test drive vehicle. Using scan tool, select GOV and 3-4 SHIFT VALVE SYSTEM TEST. Select 4th gear while monitoring pressure gauge. Governor pressure should increase to greater than 20 psi (1.4 kg/cm2 ) and OD pressure should increase to greater than 40 psi (2.8 kg/cm2 ). If pressures are as specified, go to next step. If pressures are not as specified, go to step 11 .
9. 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.
10. Drain transmission fluid and remove oil pan. If transmission fluid is burnt or contains excessive debris, repair as necessary. If transmission fluid is okay, go to step 17 .
11. Leave gauges connected. Replace 3-4 shift solenoid. See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS. Start engine and allow engine and transmission to reach normal operating temperature. Using scan tool, select GOV and 3-4 SHIFT VALVE SYSTEM TEST. Select 4th gear while monitoring pressure gauges. Governor pressure should increase to greater than 20 psi (1.4 kg/cm2 ) and OD pressure should increase to greater than 40 psi (2.8 kg/cm2 ). If pressures are as specified, testing is complete. If pressures are not as specified, an internal transmission malfunction exists. Repair transmission as necessary, paying attention to seals and clutches related to OD clutch. See appropriate OVERHAUL article.
12. Check transmission fluid for proper level and for any debris. Fill or repair transmission as necessary. See appropriate SERVICING article in AUTOMATIC TRANSMISSIONS. If fluid level and condition are okay, go to next step.
13. Start engine. Using scan tool, perform TCC SYSTEM TEST. If engine stalls, go to next step. If engine does not stall, go to step 16 .
14. Using scan tool, select GOV and 3-4 SHIFT VALVE SYSTEM TEST. Select 4th gear. If engine stalls, go to next step. If engine does not stall, go to step 17 .
15. Replace TCC solenoid. See REMOVAL & INSTALLATION in appropriate SERVICING article in AUTOMATIC TRANSMISSIONS. Perform GOV and 3-4 SHIFT VALVE SYSTEM TEST. Select 4th gear. If engine stalls, repair internal transmission problem. Check for internally blocked passages. Repair as necessary. If engine does not stall, testing is complete.
16. Remove transmission. See appropriate REMOVAL & INSTALLATION article in AUTOMATIC TRANSMISSIONS. Remove oil pump. See appropriate OVERHAUL article. Inspect reaction shaft, input shaft and input shaft seal. If any parts are damaged, repair as necessary and go to next step. If all parts are okay, replace torque converter.
17. 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.