P0740 Code: Torque Converter Clutch Solenoid Circuit/Open
The computer found an open or faulty circuit to the torque converter clutch solenoid, so lockup is disabled.
Unverified: this manufacturer-specific definition comes from a single source or varies by model. Confirm it with a brand-specific scan tool.
At a glance
Severity: Low
- Meaning
- Torque Converter Clutch Solenoid Circuit/Open
- System
- Transmission · Powertrain
- Safe to drive?
- Yes, short term
- Typical repair cost
- $20–$1,300
- DIY difficulty
- Moderate
The torque converter clutch (TCC) solenoid is an electrically operated valve that tells the transmission hydraulics when to lock the converter at cruise. The TCM or PCM monitors the circuit while switching the solenoid, and P0740 sets when the voltage it sees doesn't match what an intact circuit should produce – most often because the circuit is open. The usual culprits are a broken wire, an unplugged or corroded connector, an open solenoid coil or a missing feed voltage. The computer then stops using lockup, so the car still drives but cruises at higher rpm. Definitions vary: Chrysler, Dodge and Jeep use P0740 on many models for 'TCC – no rpm drop at lockup', which is a hydraulic or mechanical fault rather than a wiring problem.
Can I keep driving? Generally safe to drive. Expect a few hundred rpm more at highway speed and a warmer transmission, so avoid long towing trips until the circuit is repaired.
How to read P0740
- P Powertrain
- 0 Generic (SAE)
- 7 Transmission
- 40 Specific fault
Symptoms
- Check engine light with no obvious drivability change
- Engine rpm 200–400 higher than normal at steady highway speed
- Noticeably lower highway fuel economy
- Tachometer never shows the small drop that lockup normally causes around 40–50 mph
- Transmission temperature higher than usual on long drives
- Sometimes shift solenoid codes at the same time, if they share a power feed
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Broken wire or loose, corroded connector between the computer and the transmission
- Open TCC solenoid coil
- Blown fuse or lost power feed to the transmission solenoids
- Brake switch in the TCC circuit misadjusted or failed (older GM designs)
- Internal harness or case pass-through connector damaged or fluid-soaked
- Faulty driver circuit or ground in the TCM/PCM
- Low battery or charging voltage
Diagnosis step by step
Look at the other codes
If shift solenoid codes such as P0750 or P0755 are stored together with P0740, suspect the shared power feed or fuse before the TCC solenoid itself. A lone P0740 points to the TCC solenoid or its own wire.
Tools: OBD-II scanner
Inspect the harness and connector
Follow the harness from the transmission connector toward the computer, paying attention to spots near the exhaust, crossmember and anywhere recent work was done. Check the connector for pushed-back pins, corrosion or fluid inside.
Tools: Flashlight, Screwdriver
Check the power feed
With the key on, engine off, measure voltage on the solenoid feed pin at the transmission connector. You should see battery voltage, about 12.4–12.6 V; none means a fuse, relay or feed wire problem.
Tools: Multimeter
Measure the solenoid resistance
Measure across the TCC solenoid pins at the transmission connector and compare with the specification. On/off TCC solenoids are often roughly 10–40 ohms and pulse-width-modulated types lower; an 'OL' reading means an open coil or internal harness.
Tools: Multimeter
Check the brake switch input
On older GM trucks and cars, the TCC solenoid feed passes through a brake pedal switch that opens when you brake. Watch the brake switch status on the scan tool; a switch that stays 'applied' or is misadjusted after brake work keeps lockup from working.
Tools: OBD-II scanner, Multimeter
Command the solenoid
Use the scan tool's output test or a road test at 45–55 mph to command lockup while monitoring the circuit with a test light or meter. If the feed and solenoid are good but the computer never switches the circuit, the driver side of the TCM/PCM is suspect.
Tools: OBD-II scanner, Multimeter
Where the parts are
- 1Battery
- 2Alternator
- 3Engine computer (ECM)
- 4CAN bus
- 5Transmission
- 6Wheel speed sensor
- 7High-voltage battery
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Repair wiring or clean and secure connector | Yes | $80–$300 |
| Replace fuse and find the cause of the blown fuse | Yes | $20–$200 |
| Adjust or replace brake pedal switch | Yes | $60–$200 |
| Replace TCC solenoid or internal harness | No | $250–$700 |
| Replace and program TCM/PCM | No | $500–$1,300 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Chevrolet
Older GM trucks and cars with the 4L60E route the TCC solenoid's power through a brake pedal switch, sometimes combined with the cruise release switch. A misadjusted or failed switch is a well-known reason for lost lockup and TCC circuit codes.
Jeep
On many Jeep, Dodge and Chrysler models, P0740 is defined as 'torque converter clutch – no rpm drop at lockup'. It means lockup was commanded but engine rpm didn't fall, so the diagnosis follows the hydraulic path like a TCC slip code rather than a wiring check.
Field data
| Dodge | 5 | Grand Caravan, Journey, Nitro | |
|---|---|---|---|
| Chrysler | 2 | Town And Country | |
| Toyota | 2 | Highlander |
Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.
Emissions / smog test impact
Will fail
A check engine light caused by P0740 fails OBD emissions testing. After fixing the circuit, clear the code and drive until the monitors are ready again.
Frequently asked questions
Can I drive with P0740?
Yes, usually. The transmission simply stops locking the converter, so you use more fuel at highway speed and the fluid runs warmer. Get it fixed before towing or long trips in hot weather.
Why did P0740 appear right after a transmission service?
Dropping the pan or moving the harness can disturb the case connector or pinch a wire. Check that the connector is fully seated and locked before looking for anything more complicated.
What's the difference between P0740 and P0741?
P0740 is about the electrical circuit that controls lockup. P0741 means the circuit seems fine but the converter clutch slips or doesn't engage properly, which is a hydraulic or mechanical problem.