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P0740 — Torque Converter Clutch Circuit Fault

P0740 is the general torque converter clutch (TCC) circuit code. Depending on the manufacturer it is set for an electrical fault in the TCC solenoid circuit — an open or a short — or for the clutch simply never engaging when the transmission controller commands it. The torque converter clutch is what mechanically locks the engine to the transmission at cruise, removing the slip that a fluid coupling always has. When it does not work, the engine turns faster than it should for a given road speed, fuel economy drops, and the transmission runs hotter than it was designed to.

P0740 means torque converter clutch circuit fault. A vehicle usually stays drivable short-term with this code, but it should be diagnosed promptly. The most common cause is failed tcc solenoid (typically $300–$900). Causes and cost vary by make and model; confirm the root cause before replacing parts.

Severity: high powertrain Safe to drive (short term)

Reviewed by MECH AI Editorial · Last verified

What does P0740 mean?

P0740 is the general torque converter clutch (TCC) circuit code. Depending on the manufacturer it is set for an electrical fault in the TCC solenoid circuit — an open or a short — or for the clutch simply never engaging when the transmission controller commands it. The torque converter clutch is what mechanically locks the engine to the transmission at cruise, removing the slip that a fluid coupling always has. When it does not work, the engine turns faster than it should for a given road speed, fuel economy drops, and the transmission runs hotter than it was designed to.

What are the symptoms of P0740?

What causes P0740?

Cause Likelihood Estimated repair (USD)
Failed TCC solenoid Most common $300–$900
Damaged wiring or fluid-contaminated external transmission connector Common $100–$500
Low transmission fluid level or contaminated fluid Common $100–$400
Stuck TCC control valve in the valve body Common $400–$1,500
Worn or burned torque converter clutch friction material — Requires torque converter replacement — a major job. Occasional $1,800–$4,500
Failed TCM or PCM driver for the TCC circuit Rare $500–$1,500
Internal transmission damage allowing fluid bypass Rare $2,500–$6,500

Repair costs are typical US ranges and vary by make, model, model year, and labor rate. A diagnostic trouble code is a symptom, not a guaranteed failed part — confirm the root cause before replacing anything.

Is it safe to drive with P0740?

In most cases a vehicle stays drivable for short trips with P0740 active, but you should diagnose and repair it promptly. This is a high-severity code — ignoring it can lead to further damage or a failed emissions test. Exact tolerance depends on your specific make and model.

How to diagnose P0740

  1. Check transmission fluid level and condition

    This comes first every time. Many modern transmissions have no dipstick and require a specific procedure — fluid at a defined temperature, engine running, vehicle level — to check the level at all. Follow the procedure for this vehicle. Fluid that smells burnt or carries clutch material tells you the problem is internal and no solenoid will fix it.

    Tools: Vehicle-specific service procedure, Replacement fluid (if needed)

  2. Pull all transmission codes, not just the engine codes

    P0740 on its own is one repair scope. P0740 alongside gear-ratio codes or a pressure code means broader problems that a solenoid replacement will not resolve. Read the TCM directly rather than relying on a generic scan of engine codes only.

    Tools: Scan tool with TCM access

  3. Watch TCC command against actual lockup on the road

    At a steady highway cruise, graph commanded TCC state alongside engine RPM and vehicle speed. On a healthy system the RPM drops noticeably at the moment lockup engages. Command with no RPM drop confirms the clutch is not engaging mechanically — which is the condition, not yet the cause.

    Tools: Scan tool with TCC and live RPM PIDs

  4. Test the TCC solenoid circuit electrically

    Locate the TCC solenoid pin at the external transmission connector using the wiring diagram, and measure resistance. Compare against the specification for this transmission. Infinite resistance means an open coil or an open circuit; a near-zero reading means a shorted solenoid.

    Tools: Multimeter, Wiring diagram

  5. Inspect the external transmission connector for fluid

    A failed case seal lets transmission fluid wick up inside the wiring harness and into the connector. The result mimics a failed solenoid on a multimeter while the solenoid is perfectly fine. If you find fluid in the connector, the repair is the seal and often a section of harness.

    Tools: Connector unlock tool, Flashlight

How do I fix P0740?

P0740 by make and model

Select your exact year, make, and model below to get a P0740 diagnosis tuned to your vehicle's known failure patterns, recalls, and TSBs.

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Related diagnostic codes

Common symptoms of P0740

P0740 often shows up as one of these symptoms. Start from what your car is actually doing:

P0740: frequently asked questions

What does diagnostic trouble code P0740 mean?

P0740 is the general torque converter clutch (TCC) circuit code. Depending on the manufacturer it is set for an electrical fault in the TCC solenoid circuit — an open or a short — or for the clutch simply never engaging when the transmission controller commands it. The torque converter clutch is what mechanically locks the engine to the transmission at cruise, removing the slip that a fluid coupling always has. When it does not work, the engine turns faster than it should for a given road speed, fuel economy drops, and the transmission runs hotter than it was designed to.

What are the symptoms of P0740?

Check Engine Light is illuminated. Engine RPM at highway cruise is higher than normal for the same speed. Noticeable fuel economy drop, worst on the highway. No sensation of the transmission "shifting" into lockup at cruise. Transmission fluid running hot, especially when towing. Often paired with P0700 from the transmission controller

What causes P0740?

Failed TCC solenoid (most-common). Damaged wiring or fluid-contaminated external transmission connector (common). Low transmission fluid level or contaminated fluid (common). Stuck TCC control valve in the valve body (common). Worn or burned torque converter clutch friction material (occasional). Failed TCM or PCM driver for the TCC circuit (rare). Internal transmission damage allowing fluid bypass (rare)

Is it safe to drive with P0740?

In most cases a vehicle stays drivable for short trips with P0740 active, but it should be diagnosed and repaired promptly — this is a high-severity code. Ignoring it can lead to further damage or a failed emissions test. Specific tolerance varies by make and model.