# P0740: Torque Converter Clutch Solenoid Circuit/Open **Verdict:** Drive to a shop this week Transmission - Generic OBD-II code, applies to all gasoline cars and light trucks sold in the US since 1996. - **Typical cost:** $100-$1,200 - **Urgency:** This week - **Most likely:** TCC solenoid or its wiring - **DIY?:** Electrical checks only ## Quick answer P0740 means the computer found an electrical problem in the torque converter clutch solenoid circuit, such as an open wire or a solenoid that is not drawing the expected current. With the circuit down, the converter usually cannot lock up, so engine RPM stays higher at highway speed. Wiring, a connector, or the solenoid itself are the usual causes. ## What does P0740 mean? The torque converter clutch (TCC) locks the engine to the transmission at steady cruising speeds so the fluid coupling inside the converter stops slipping. That drops engine RPM, reduces transmission heat, and improves fuel economy. The computer applies the clutch by switching on the TCC solenoid, an electric valve usually mounted on the valve body inside the transmission, which then sends fluid pressure to the clutch. The computer's output driver watches the solenoid circuit's voltage or current whenever it switches the solenoid on or off. P0740 sets when that electrical feedback is wrong, such as an open circuit with no current flowing, for a set time. It is an electrical code, unlike P0741, which means the circuit works but the clutch still slips. On some vehicles, related codes such as P0743 cover other circuit faults. Most vehicles stop using lockup until the fault is repaired. ## What are the symptoms of P0740? - Engine RPM higher than usual at highway cruise - Lower fuel economy - No small RPM drop when cruising at a steady speed - Transmission fluid running hotter than normal - Check engine light on ## What causes P0740? Ranked from most to least likely. Check them in this order: the cheap, common causes first. 1. **Open or shorted TCC solenoid coil** (most common). The solenoid's thin copper winding sits in hot transmission fluid and cycles on and off constantly during highway driving. Over time the winding can break open or short internally. A resistance test across the solenoid terminals, compared with the maker's specification, shows the fault, though on some solenoids it appears only once the transmission is hot. 2. **Wiring or case connector fault** (common). The solenoid wires leave the transmission through a sealed case connector, and its seal can leak fluid into the pins or let water in. Outside, the harness can be chafed, corroded, or damaged near the exhaust. A fault that changes when the connector is wiggled, or fluid found inside the connector, points here rather than at the solenoid. 3. **Blown fuse or solenoid power supply** (less common). On many vehicles the transmission solenoids share a fused power feed, sometimes through a relay. A blown fuse or failed relay drops power to the TCC solenoid and others at once, so several solenoid codes appear together. Checking the fuse, then power at the solenoid connector with the key on, is a quick early test. 4. **Failed solenoid pack or internal harness** (less common). Some transmissions combine the TCC solenoid with other solenoids in one pack, or use an internal wiring harness inside the pan. Heat and vibration can crack the internal harness insulation or break a terminal. The repair means removing the pan, and sometimes replacing the whole solenoid assembly instead of a single solenoid. 5. **Transmission computer driver fault** (rare). The computer switches the solenoid through an internal driver circuit, and a shorted solenoid or wire can damage that driver. If the solenoid and wiring test good but the command never reaches the connector, the computer is suspect. Fix any shorted solenoid first, or a replacement computer can fail the same way. ## How do you diagnose P0740? 1. Read all transmission codes and note any other solenoid or voltage codes stored with P0740. 2. Check the transmission solenoid fuse and power feed. 3. Measure TCC solenoid resistance at the transmission connector, hot and cold if possible, against the maker's spec. 4. Inspect the case connector for fluid and the harness for damage, then check the circuit to the computer. 5. Command lockup with a scan tool on a road test and watch for the RPM drop. ## How do you fix P0740, and what does it cost? | Fix | Typical cost | What it involves | | --- | --- | --- | | Repair wiring, connector, or fuse | $100-$400 | Often the fix when fluid has leaked into the case connector. | | Replace TCC solenoid | $300-$800 | Usually reached by removing the transmission pan. | | Replace solenoid pack or internal harness | $450-$1,200 | When the solenoid is part of an assembly or the harness is damaged. | Full price breakdowns: [transmission fluid change cost](/cost/transmission-fluid-change). ## Is it safe to drive with P0740? > **Drive to a shop this week.** It is usually safe to drive in the short term, because the transmission still shifts and simply stops locking up. Expect lower fuel economy and more heat, so avoid towing and long, hot highway trips until it is repaired. ## Will P0740 fail an emissions test? P0740 turns on the check engine light, which fails an OBD-II emissions test in most states. Lockup affects fuel use and emissions, so the circuit is monitored. Clearing the code resets the readiness monitors, and an open circuit is usually detected again on the next drive, so repair it before testing. ## After the repair: clearing P0740 After the repair, clear the codes and drive at a steady highway speed. You should feel or see a small drop in RPM when lockup engages, and a scan tool should show the TCC commanded on with low converter slip. No returning code over several highway drives means the circuit is fixed. ## How to prevent P0740 - Change transmission fluid on schedule, since hot, worn fluid shortens solenoid life. - Fix leaks at the transmission case connector before fluid wicks into the harness. - Keep wiring clipped clear of the exhaust after any underbody repair. - Avoid towing beyond your vehicle's rating, since extra heat stresses solenoids and wiring. ## Codes often seen with P0740 - [P0741](/codes/p0741): Torque Converter Clutch Solenoid Circuit Performance/Stuck Off - [P0700](/codes/p0700): Transmission Control System (MIL Request) - [P0750](/codes/p0750): Shift Solenoid "A" - [P0562](/codes/p0562): System Voltage Low ## Frequently asked questions ### Can I drive with a P0740 code? Usually yes, for a short time. With the clutch circuit down, the converter stays unlocked, so the transmission shifts but runs hotter and uses more fuel. Avoid towing and long highway trips in hot weather, and get it repaired before the extra heat wears the fluid and clutches. ### What is the difference between P0740 and P0741? P0740 is an electrical code: the computer sees an open or faulty circuit to the torque converter clutch solenoid. P0741 means the circuit works but the clutch still slips or does not apply, a hydraulic or mechanical problem. An electrical P0740 is usually cheaper to fix than a slipping converter. ### What does a torque converter clutch do? The torque converter clutch locks the engine to the transmission at steady speeds, removing the slip of the fluid coupling. That lowers engine RPM, cuts transmission heat, and improves fuel economy, especially on the highway. When it does not work, the car still drives but runs at higher RPM when cruising. ### How much does it cost to fix P0740? Most P0740 repairs cost $100 to $1,200 at an independent shop. A wiring, connector, or fuse repair runs about $100 to $400 and a new TCC solenoid $300 to $800. If the solenoid is part of a pack or the internal harness is damaged, expect $450 to $1,200. ### Can a bad TCC solenoid cause stalling? It can if the solenoid sticks applied, because a locked converter at a stop acts like a manual car with the clutch engaged and can stall the engine. That pattern fits a stuck-on fault better than an open circuit. With P0740 alone, the converter usually just never locks. ### Where is the TCC solenoid? On most automatics the torque converter clutch solenoid bolts to the valve body inside the transmission, under the oil pan. On some designs it is part of a solenoid pack or combined module. Reaching it usually means draining fluid and removing the pan, then refilling with the correct fluid. ### Can I fix P0740 myself? You can check fuses, inspect the case connector for fluid or corrosion, and measure solenoid resistance with a multimeter if you have the spec. Replacing a solenoid under the pan is possible for experienced DIYers, but refilling to the correct level is tricky on many sealed transmissions. ### Will P0740 hurt my transmission? Not right away, but over time it can. Without lockup, the converter slips constantly at cruise, creating extra heat that breaks down fluid and wears clutches. A short delay is usually fine, while months of driving, especially towing or in hot weather, add wear you could avoid. ### Why is my RPM high on the highway? Higher-than-normal cruise RPM often means the torque converter clutch is not locking up, which P0740 or P0741 can explain. Other causes include a transmission that is not shifting into top gear or a slipping clutch. A scan tool showing commanded gear and converter slip tells which it is. ### Will P0740 fail an emissions test? Yes, in most states P0740 fails an OBD-II emissions test because it turns on the check engine light. The torque converter clutch affects fuel economy and emissions, so the circuit is monitored. Repair it, clear the codes, and drive several days so the readiness monitors complete before testing. ## Sources - [SAE J2012: Diagnostic Trouble Code Definitions](https://www.sae.org/standards/content/j2012_201812/) - [EPA: On-Board Diagnostics (OBD)](https://www.epa.gov/state-and-local-transportation/vehicle-emissions-board-diagnostics-obd) ## Other transmission codes - [P0700 Transmission Control System (MIL Request)](https://diagxcar.com/codes/p0700) - [P0705 Transmission Range Sensor "A" Circuit (PRNDL Input)](https://diagxcar.com/codes/p0705) - [P0715 Input/Turbine Speed Sensor "A" Circuit](https://diagxcar.com/codes/p0715) - [P0717 Input/Turbine Speed Sensor "A" Circuit No Signal](https://diagxcar.com/codes/p0717) - [P0720 Output Shaft Speed Sensor "A" Circuit](https://diagxcar.com/codes/p0720) - [P0730 Incorrect Gear Ratio](https://diagxcar.com/codes/p0730) - [P0731 Gear 1 Incorrect Ratio](https://diagxcar.com/codes/p0731) - [P0732 Gear 2 Incorrect Ratio](https://diagxcar.com/codes/p0732) - [P0741 Torque Converter Clutch Solenoid Circuit Performance/Stuck Off](https://diagxcar.com/codes/p0741) - [P0750 Shift Solenoid "A"](https://diagxcar.com/codes/p0750) ## Symptoms - [Why is my car getting bad gas mileage?](https://diagxcar.com/symptoms/poor-gas-mileage) ## Repair costs - [Transmission fluid change cost](https://diagxcar.com/cost/transmission-fluid-change): $120-$350 --- Source page: https://diagxcar.com/codes/p0740 Updated: 2026-11-03 General information, not a substitute for a qualified mechanic.