Buick Century 2001: the Service Engine Soon warning light came on and was diagnosed as code P0740 Torque Converter Clutch Circuit Open. The transmission fliud has been replaced and the Engine Service Soon light soon returned, after a few miles of driving. What could I be facing as possible repair bills, from low to high.

P0740 is the torque converter malfunction code. The converter is in between the engine and transmission. The fluid that you are seeing is transmission fluid. It needs to go to a mechanic to narrow it down from there.

P0740 torque converter malfunction
Possible causes
Low or dirty transmission fluid
Faulty torque converter clutch solenoid valve
Torque converter clutch solenoid valve harness is open or shorted
Torque converter clutch solenoid valve circuit poor electrical connection

P0562 charging system voltage low
Possible causes
Low battery charge
Defective battery
Faulty alternator
Problem with belt
Open or shorted system voltage circuit

On some cars, there is a TCC solenoid in the transmission which can be replaced by removing the bottom pan. In some cars this solenoid can't be accessed without major disassembly.

Yes, it is a Transmission code: PO742 Torque Converter Clutch Circuit Stuck On

P0740 - Torque Converter Clutch Malfunctionhttp://engine-codes.com/p0740.htmlForum CodePossible causes- Low transmission fluid level
- Dirty transmission fluid
- Faulty torque converter clutch solenoid valve
- Torque converter clutch solenoid valve harness or connectors
- Torque converter clutch solenoid valve circuit is open or shorted When is the code detected?Diagnostic trouble code P0740 is detected when TCM detects an improper voltage drop when it tries to operate the solenoid valve.

P0700 TCM has requested PCM to run on Check engine light to alert to a fault in the automatic transmission.

P0740 - Torque Converter Clutch Malfunction
Possible causes- Low transmission fluid level
- Dirty transmission fluid
- Faulty torque converter clutch solenoid valve
- Torque converter clutch solenoid valve harness or connectors
- Torque converter clutch solenoid valve circuit is open or shorted

P0743 - Torque Converter Clutch Circuit Electrical
Symptoms - Engine Light ON (or Service Engine Soon Warning Light) Possible causes - Faulty torque converter clutch solenoid valve
- Torque converter clutch solenoid valve harness or connectors
- Torque converter clutch solenoid valve circuit is open or shorted
- Low transmission fluid level
- Dirty transmission fluid
Tech notes This is an electrical problem code. Could be a problem to the harness to the TCC solenoid, the TCC solenoid connector or the TCC solenoid it self.

P0740 JEEP - Torque Converter Clutch Circuit
Symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Transmission shift shock
- Vehicle may not shift into the highest gear

Possible causes
- Low transmission fluid level
- Dirty transmission fluid
- Faulty torque converter clutch solenoid valve
- Torque converter clutch solenoid valve harness or connectors
- Torque converter clutch solenoid valve circuit is open or shorted

When is the code detected?
Torque Converter Clutch (TCC) unlocked for 10 sec., ECM commands converter lock-up and did not record engine speed drop.

P0740 JEEP Description
The torque converter clutch solenoid valve is activated, with the gear in D4, by the Transmission Control Module (TCM) in response to signals sent from the vehicle speed and the Engine Control Module (ECM). Lock-up piston operation will then be controlled. When the torque converter clutch solenoid valve is activated, the torque converter lockup clutch will engage creating a 1 to 1 RPM ratio between the transmission input shaft and the rotational speed of the torque converter.

Lock-up operation, however, is prohibited when A/T fluid temperature is too low.

When the accelerator pedal is depressed (less than 2/8) in lock-up condition, the engine speed should not change abruptly. If there is a big jump in engine speed, there is no lock-up.

I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

torque converter lock-up solenoids are at the top of the transmission on the OUTSIDE. The two came off with three bolts and the screens on mine were clogged with "lint".

P0740 is a Torque Converter Clutch Circuit Malfunction, you will need to have just this circuit tested, it is mostly just a defective Torque converter clutch solenoid in the trans or a defective connection to the trans, u do not need another overhaul.