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  Transmission Torque Converter Clutch Solenoid
   
 

... What is a Torque Converter Clutch Solenoid?
... What Does a Torque Converter Clutch Solenoid do?
... Symptoms of a Failed Torque Converter Clutch Solenoid
... Torque Converter Clutch Solenoid Replacement and Cost
... Purchase a new Torque Converter Clutch Solenoid
 

 
  Transmission Torque Converter Clutch (TCC) Solenoid:
DESCRIPTION


Positioned between the rear of the engine and the front of the transmission is the torque converter.  The torque converter is responsible for transmitting the engine's torque and power to the transmission. To prevent slipping at certain speeds (normally speeds exceeding 37 mph) a lockup clutch located inside the converter locks the engine's output drive to the transmission's input shaft to achieve a 1:1 ratio - meaning 100% of the engine's power is now reaching the transmission.

The fluid pressure that applies and releases the torque converter lockup clutch is controlled by the torque converter clutch solenoid.  The opening and closing of the TCC solenoid valve is controlled by the transmission control module (TCM) or powertrain control module (PCM), depending on the vehicle. 


Faulty Transmission Torque Converter Clutch Solenoid:
SYMPTOMS -
Failed in the Closed Position


With respect to drivability and performance, a malfunctioning torque converter clutch solenoid (one that fails in the closed position) may not be noticeable.  However, if you pay close attention to your gas mileage, you will see an increase in fuel consumption because the engine and transmission are not locking up at highway speeds because the faulty solenoid.  Thus, you have slipping, which causes the engine to work harder.  The harder the engine works the more fuel it consumes.  Slipping also generates heat.  Any time a transmission overheats, some internal damage occurs. 

NOTE: To say that the lockup torque converter LOCKS the engine and transmission together isn't completely accurate because slipping can still occur if the vehicle has a heavy enough load.  A transmission that slips while in lockup because the system is overloaded will generate tremendous heat.  These situations normally end with complete transmission failure.

A faulty torque converter clutch solenoid normally sets a Diagnostic Trouble Code (DTC), which causes the Check Engine Light to come on.  A faulty torque converter clutch solenoid will normally set diagnostic trouble code P0740.

P0740 Torque Converter Clutch Circuit Malfunction  
  Code Description:
 
A faulty Torque Converter Clutch (TCC) Solenoid  
A damaged transmission wiring harness, loose connection or open circuit in the system  
A problem in the Transmission Control Module (TCM) or Powertrain Control Module (PCM), depending on the vehicle.  

RELATED CODES  
P0741 Torque Converter Clutch Circuit Performance or Stuck Off
P0742 Torque Converter Clutch Circuit Stock On  
P0743 Torque Converter Clutch Circuit Electrical    
P0744 Torque Converter Clutch Circuit Intermittent   

DTCs provided above are generic codes that apply to 1996 and newer vehicles. These codes may not apply to all vehicles. Vehicle manufacturers may use manufacturer specific DTC codes that are different from the codes shown here.

Faulty Transmission Torque Converter Clutch Solenoid:
SYMPTOMS -
Failed in the Open Position

The symptoms are different a torque converter clutch solenoid that fails in the open position... The symptoms of a torque converter clutch solenoid that fails while in the open position are quite different from a solenoid that fails in the closed position, as described above. When the solenoid is open, the engine is locked to the transmission so there is no transmission slip. With the transmission unable to slip, the engine will stall when the vehicle comes to a stop.

This type of solenoid failure will set a Diagnostic Trouble Code causing the Check Engine Light to illuminate. The same Diagnostic Trouble Codes listed above apply.


Torque Converter Clutch Solenoid:
REPAIR INFORMATION


Once it is determined that the transmission torque converter clutch solenoid is faulty, the solenoid must be replaced. Replacing a transmission torque converter clutch solenoid can be done by most any auto repair shop, automobile dealership service center or you can do-it-yourself "DIY".

Torque Converter Clutch Solenoid:
REPLACEMENT COST


The cost to replace a failed transmission torque converter clutch solenoid is determined, in part, by the vehicle year, make and model. Other factors, such as where the work is done (whether at a local auto repair shop, car dealership or you do-it-yourself) also factors heavily into the cost of repair. If you choose to replace the solenoid yourself, the parts supplier you purchase the solenoid from will factor into your total repair.

Below are costs for replacing the transmission torque converter clutch solenoid in four different vehicles. You can use these costs as a guide in estimating your cost.


DIY costs assume transmission fluid is reused. Replacing the fluid with new ATF increases the cost.  ATF costs between $5 and $10 per quart. You will need between 3 and 5 quarts.


Diagnosing a failed transmission solenoid with Check Engine Light

A failed transmission solenoid will normally set a diagnostic trouble code (DTC), which will cause the check engine light to illuminate. In these instances, an OBD-II scan of your vehicle's computer will provide information pointing to the faulty solenoid. The DTC information (or explanation) will almost always include a statement indicating that the problem may be an open circuit in the transmission electrical system. Therefore, before replacing a transmission solenoid, it should be tested first.

Diagnosing any Transmission Problem with NO Check Engine Light

Transmission problems with no check engine light are more difficult to diagnose. In these instances, a diagnostic scan using a special transmission scanner is necessary. This will necessitate a visit to a transmission shop or dealership to have the scan performed. General auto repair shops typically do not have the type of scanner needed to diagnose automatic transmissions. A professional transmission scan costs between $60 and $125. The shop doing the diagnostics will normally waive the diagnostic fee if they do the repair.

Fail Safe (or Limp Mode)

A failed transmission solenoid or an open circuit anywhere in the electrical system may cause the transmission to go into Fail Safe (or "limp" mode as it is also called) in order to protect the transmission from internal damage that might be caused by the condition.  In fail safe/limp mode, the transmission locks in either 2nd or 3rd gear and will have limited functionality. When the transmission is in fail safe mode, the vehicle should only be drive home or to the repair shop. Maximum speed while in limp mode is around 30 mph.

WARNING: Continuing to drive the vehicle with the transmission in limp mode and/or driving faster than the recommended fail safe speed will cause the transmission to overheat. Excessive heat build will cause serious internal damage to the transmission.
   
 
   
   
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