P0744 – Torque converter clutch (TCC) solenoid -circuit intermittent
| Code | Fault Location | Probable Cause |
|---|---|---|
| P0744 | Torque converter clutch (TCC) solenoid -circuit intermittent (Buy Part On Amazon) | Wiring, poor connection, TCC solenoid, ECM/PCM!TCM |
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Table of Contents
- What Does Code P0744 Mean?
- Where is the P0744 sensor located?
- What are the common causes of code P0744 ?
- Get Help with P0744
What Does Code P0744 Mean?
OBD II fault code P0744 is a generic code that is defined as “Torque converter clutch (TCC) solenoid -circuit intermittent”, and is set when the PCM (Powertrain Control Module) detects an intermittent loss of continuity in the control circuit of the solenoid (or on some applications, the pair of solenoids) that controls the operation of the torque converter lockup clutch.
The purpose of the torque converter is to transmit the engines’ power to the transmission, an while torque converters that are not fitted with lockup clutches are reasonably efficient, the advent of torque converter lockup clutches has greatly enhanced torque converters’ power transmission ability.
In simple terms, a torque converter is a hollow drum that is attached to the engine, and encloses a turbine that is attached to the transmission, with no direct contact between the drum and the turbine. Both components are fitted with blades, or vanes; as the outer drum rotates, its vanes pick up transmission fluid (that is contained within the drum), that is then flung against the vanes of the turbine, causing the turbine to rotate, thereby transmitting the engine’s power to the transmission.
However, this method of power transmission necessarily results in an unavoidable loss of some of the engines’ power even in the most efficient torque converters , since it is the shear strength of the transmission fluid, and not a mechanical link, that determines how much of the engines’ power is transferred onto the transmission turbine. Put in another way, this means that since some transmission fluid is forced through the small gap between the vanes on the drum and those on the turbine as the outer drum rotates, the fluid that is lost in this way cannot contribute to the transmission of power from the engine to the transmission.
This power loss is known as “slippage”, and while it can vary greatly between applications, it always means that not all of the engines’ power is transmitted to the transmission, which in turn, means that not all of the fuel being burnt in the engine is converted into energy that reaches the driving wheels. In short, this means that automatic applications without torque converter lockup clutches are less fuel-efficient than applications that do have torque converter lockup clutches.
To address all of these issues, car manufacturers have developed mechanical clutches that lock the two halves of the torque converter together; much like a clutch in a manual application that forms a mechanical link that locks the engine and transmission together. The practical advantage of this is not only that slippage can be eliminated, which increases fuel efficiency and reduces emissions, but also that under certain conditions, slippage can be induced to both make gear shifts smoother, and to protect vulnerable transmission components against the effects of over torque conditions.
In terms of operation, a torque converter lockup clutch depends on pressurized fluid either to engage, or to disengage friction surfaces that loosely resemble clutch components found in manual applications. Pressurized fluid is supplied by the transmission pressure pump, and an electronically operated solenoid is used to direct/control/regulate the flow of pressurized fluid to and from the lockup clutch.
In a fully functional system, the lockup clutch is typically engaged when the vehicle is in motion, causing all of the engines’ power to be transmitted to the transmission since there is no clutch slippage present. When the PCM determines (based on input data from (among others) the engine speed sensor, vehicle speed sensor, and throttle position sensor(s) that a gear shift may be harsh, it may momentarily relieve some of the pressure keeping the lockup clutch engaged to induce some slippage. This has the effect of “smoothing out” gearshifts, especially during hard acceleration, since some of the engine’s torque is now being bled off by the differential rotation of the two halves of the torque converter that was brought about by the induced slippage of the lockup clutch.
From the above, it should be obvious that for the torque converter lockup clutch to work as intended, all of the components in the system need to be in perfect working order. Thus, should the PCM detect an issue such as an intermittent loss of continuity in the lockup clutch’s’ control solenoid(s) and/or associated control circuits, it will recognize that it can no longer control the lockup clutch effectively, which very often causes severe drivability issues. When this occurs, the PCM (or other control module) will set code P0744, and may also illuminate a warning light.
Where is the P0744 sensor located?
The image above shows a typical torque converter lockup clutch control solenoid (indicated by the arrow) fitted into the valve body of a BMW transmission.
Note though that while this solenoid is located inside the transmission on many applications, there are also many transmissions on which the torque converter lockup clutch control solenoid is located outside of the transmission.
WARNING: When diagnosing this code, it is critically important to refer to the manual for the affected application to locate and identify the torque converter lockup clutch control solenoid(s) correctly, since failing to do this could result in severe, if not always fatal damage to the transmission.
What are the common causes of code P0744 ?
Note that code P0744 rarely indicates a faulty transmission, or a general failure of mechanical components in the transmission or torque converter. However, depending on the exact nature of the electrical problem in the control circuit of the torque converter lockup clutch, this code can sometimes cause a variety of transmission and lockup clutch related codes that typically set as the result of P0744, as opposed to the additional codes having caused P0744 to set. Nonetheless, some common causes of code P0744 could include the following-
- Damaged, burnt, shorted, disconnected, or corroded wiring and or connectors in the affected control circuit
- Defective torque converter lockup clutch control solenoid(s), but note that in cases where a pair of solenoids control the clutch, it is always preferable to replace both solenoids to prevent a recurrence of the problem
- Failed or failing PCM or other control module, including the TCM (Transmission Control Module). Note though that these are rare events, and the fault must therefore be sought elsewhere before any control module is replaced
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My nissan sentra 2010 miles 78000 mr20de 2.0L has a trouble code of p0744 it comes and goes which is werid but anyways only shows up after i travel to Laughlin from las vegas. as soon as i hit 70mph it gets super high pitched and if i rev as hard it wont pass 4000 rpms
My 2010 Nissan Rogue is doing the same thing. Did you get your Sentra repaired?
i actually traded it in because i wouldnt be able to buy the solenoid by itself i would have to buy the valve body with all the solenoids.which was 1000 bucks i didnt have
Mine is still under warranty. They replaced the valve assembly without charging me. But I am going to sell the car, because I am afraid that more trouble is on the way.
I have a 2001 nissan maxima with RE4F04B JATCO transmission in it
215K miles, around 202K miles it got P0744 and was shifting very bad. I noticed
the ATF fluid very dirty, so I did a Slow ATF flush. via 3 drain fill with few thousand miles between. I used Valvoline MaxLife Full Sync ATF. along the way Lucus and SeaFoam TransTune addives were used and helped greatly. Its shift normal now in 1,2 and Reverse. it will shift fine into 3rd. but if you floor it while in 3rd it will Slip out of gear into N.
But let off gas it slips right back in gear. Its almost like its loose ATF pressure. basically the TCC is slipping in and out of lock up. My question does it need New Shift Solenoids Block which includes TCC? or could this be bad Torque Converter or Clutch. The car’s engine runs really good and leaks and burns some oil.
I have a 2002 Nissan Xterra XE 3.3L V6 4×4 AT, 174,000 miles. I am receiving a code of P0744. The vehicle will not shift into 3rd or 4th gear. Drained the fluid and dropped the pan. The fluid was darker than it should have been, but there wasn’t excessive debris in the fluid, and only one tiny speck of debris in the transmission filter screen. Changed the filter and the TCC solenoid (was clicking, demonstrated to work), with no change in vehicle performance. I then took my vehicle to a transmission shop, where after diagnostics, they told me that both 3rd and 4th gear were “gone” and my transmission would need to be rebuilt. Is there anything else it could be?