The diagnostic trouble code or DTC P0740 stands for “Torque Converter Clutch Solenoid Circuit/Open Circuit Malfunction.”
The error code basically means that the Powertrain Control Module (PCM) has caught some issue within the torque converter clutch (TCC) circuit (or torque converter clutch solenoid circuit).
The Powertrain Control Module uses the torque converter clutch to optimize car performance by lowering engine RPMs, reducing transmission fluid temperature, and improving fuel economy. If there’s any abnormality in the application of the torque converter clutch, the Powertrain Control Module will set off your check engine light (malfunction indicator lamp).
It’s important to note that many vehicle manufacturers don’t list P0740 as a possible code.
However, for the manufacturers that consider it a possible code, P0740 typically indicates that the control module (PCM or Transmission Control Module) senses an electrical fault with the torque converter clutch solenoid. It can also be an electrical fault with the solenoid’s circuit.
For some vehicles, the P0740 code is more telling of a mechanical problem with the transmission or torque converter.
The TCC solenoid valve, an electrical device, is used with the torque converter clutch pulse width modulation (TCC PWM) solenoid valve to control TCC application and release.
The TCC solenoid valve connects to the transmission case assembly extending into the pump cover. This solenoid valve acquires ignition voltage via the Off/On/Crank voltage circuit.
The PCM regulates the solenoid by providing the ground path on the torque converter clutch solenoid valve control circuit. The PCM observes the throttle position sensor voltage, the vehicle speed, and other inputs — which helps it decide when to energize the TCC solenoid valve.
So when the PCM witnesses a continuous open, short to ground, or short to power in the TCC solenoid valve circuit, DTC P0740 is triggered.
You may first notice the check engine light (malfunction indicator lamp) illuminating. Apart from the engine light, here are some of the most common symptoms that your car may experience on detecting the P0740 code:
Not all check engine light codes mean danger in driving. However, code P0740 is serious because it can easily disrupt your normal driving experience.
Located between the transmission and the engine, the torque converter equalizes the engine speed by multiplying the torque to optimize vehicle performance. That means increasing fuel efficiency and reducing the transmission fluid temp.
But when the code P0740 is triggered, it implies that the PCM isn’t fully controlling the torque converter, causing drivability issues. You don’t want to be stuck at the 3rd or 4th gear forever.
So if you suspect or detect the DTC P0740, get the issue diagnosed and fixed as soon as possible. If you don’t, you risk getting stranded on the side of the road.
This trouble code can be triggered for numerous reasons and can differ depending on whether your car is made by Volkswagen AG, Honda motor company, Mercedes, or any other manufacturer.
Here’s a quick list of the potential causes:
Code P0740 can be caused by a faulty solenoid to a very pricey internal transmission problem. That’s why there isn’t a single fix for this code.
And since the diagnostic trouble code P0740 is severe, you should let a mechanic or transmission shop do a proper inspection and handle the repairs.
Here’s how a mechanic at a transmission shop will go about it:
Note: If there’s nothing wrong with the transmission fluid, your mechanic will follow a manufacturer-recommended diagnostic procedure to fix the issue. Remember that this diagnostic code may need removing or disassembling the transmission.
After removing the transmission pan of an automatic transmission vehicle, they’ll conduct further testing of the clutch solenoid as specified by your particular vehicle’s manufacturer.
Note: Some codes related to P0740 include:
Since the trouble code can be triggered due to multiple reasons, here’s a list of different repairs that your mechanic may perform to fix the P0740 code:
Here are some FAQs related to P0740 and its affected parts:
Whether you have a Volkswagen AG or a car by the Honda motor company, it’s common to assume that the torque converter needs to be replaced or rebuilt — when it could just be a faulty TCC solenoid or dirty transmission fluid.
Another common diagnostic mistake is believing the issue is caused by an engine misfire, a driveline, or an internal transmission problem.
The trick is to look at every aspect of each problem because it can reveal the correct solution quickly and efficiently.
The fluid temp in the automatic transmission would ideally range from 170-225 degrees Fahrenheit. If the transmission is slipping, the fluid temp could go above 240 degrees.
A transmission valve body is an important component of an automatic transmission. It’s a maze-like control center made with valves, passageways, and solenoids that direct transmission fluid to where it’s required for gear changes.
So every time you move to the 2nd or 4th gear, you can thank the valve body.
No, they aren’t.
CVT fluid is for vehicles utilizing a Continuously Variable Transmission (CVT) system, which has a different mechanism than Automatic Transmission systems. Automatic transmission fluid (ATF) has a different chemical composition than CVT fluid, so they’re not interchangeable.
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