P0740: Torque Converter Clutch Circuit Malfunction
Updated November 14, 2026
The torque converter clutch locks the engine to the transmission at cruising speed to cut slip, heat and fuel use. A solenoid controlled by the transmission computer applies it. P0740 means the computer found an electrical problem in that solenoid circuit, such as an open or short, and it usually stops using the lockup clutch.
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🔧 Want to check this yourself? An OBD2 scanner reads the code; models with live data also show the sensor readings used in the checks below. See code readers and scanners from $24.99 ↓ · Which scanner do I need?
Common causes
- A failed torque converter clutch (TCC) solenoid
- Damaged wiring or a loose or corroded connector at the transmission case, including fluid leaking into the connector
- A damaged internal transmission wiring harness
- A transmission control module fault (less common)
Code meanings can vary slightly by manufacturer. Use these as a starting point and confirm with your vehicle's service information or a mechanic before replacing parts.
Symptoms
- Check engine or transmission warning light
- Higher engine RPM than usual at highway speeds
- Worse fuel economy
- On some vehicles, harsh shifting or limp mode
Is it safe to drive?
If the transmission is slipping, stuck in one gear, or the engine stalls when you come to a stop, stop driving and have it towed. If it drives normally with a steady light, drive gently and get it fixed soon; avoid towing or heavy loads, because without lockup the transmission fluid runs hotter.
How to check it with a scanner
- Plug an OBD2 scanner into the port under the dashboard and read all stored codes and the freeze-frame data (the conditions when the code set).
- Scan the transmission module for other codes, especially other solenoid codes, which can point to shared wiring or power.
- Check the transmission fluid level and condition using your vehicle's procedure; some must be checked warm with the engine running, so keep hands clear of the belts and fan.
- With the engine off, inspect the main connector at the transmission case for corrosion, bent pins or fluid inside.
- On many transmissions the solenoid is inside the pan or valve body; a shop can measure its resistance through the case connector before anything is opened.
- After a repair, clear the code and drive normally for a few days to confirm it doesn't come back.
A basic code reader shows the code; scanners with live data let you watch sensor readings, which is what you need for most of the checks above. See OBD2 scanners under $100.
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On many transmissions the TCC solenoid is part of a solenoid pack or valve body assembly, and some need the transmission computer reprogrammed or relearned after replacement; check your service information.
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Questions
What does P0740 mean?
P0740 is the generic OBD2 code for "Torque Converter Clutch Circuit Malfunction." The torque converter clutch locks the engine to the transmission at cruising speed to cut slip, heat and fuel use. A solenoid controlled by the transmission computer applies it. P0740 means the computer found an electrical problem in that solenoid circuit, such as an open or short, and it usually stops using the lockup clutch.
Is it safe to drive with P0740?
If the transmission is slipping, stuck in one gear, or the engine stalls when you come to a stop, stop driving and have it towed. If it drives normally with a steady light, drive gently and get it fixed soon; avoid towing or heavy loads, because without lockup the transmission fluid runs hotter.
How do I check P0740 myself?
Read the code and freeze-frame data with an OBD2 scanner, then: Scan the transmission module for other codes, especially other solenoid codes, which can point to shared wiring or power. Check the transmission fluid level and condition using your vehicle's procedure; some must be checked warm with the engine running, so keep hands clear of the belts and fan. With the engine off, inspect the main connector at the transmission case for corrosion, bent pins or fluid inside. On many transmissions the solenoid is inside the pan or valve body; a shop can measure its resistance through the case connector before anything is opened.
Related codes
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