What P0740 means
There's an electrical problem in the circuit that controls the torque converter clutch. The clutch won't lock up, so rpm stays higher at highway speed and fuel economy drops.
How the engine computer detects it
The torque converter clutch (lock-up) connects pump and turbine mechanically; a solenoid – on/off, pulse-width modulated or proportional – moves a control valve in the valve body. Slip is engine speed minus turbine speed. Manufacturers do not use P0740–P0744 uniformly: Ford uses P0740 for open, P0742 for short to ground and P0744 for short to power, and reports stuck on as P2758. P0740 concerns the control circuit of the converter clutch solenoid. Ford flags an open circuit when the driver feedback line disagrees with the command for 0.5–5 s, with MIL; a 2006 GM table checks 0/12 V with more than 43 of 50 failed counts after two trips – newer GM units use P2761/P2763/P2764. FCA's Ram 6.7 reads P0740 as converter slip out of range and moved it to two trips by software in 2013. The clutch is then switched off: higher engine speed when cruising, more fuel, hotter fluid.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check engine light or transmission warning
- No lock-up: engine speed about 100–300 rpm higher when cruising
- Higher fuel consumption, hotter transmission fluid
Common causes
- Open or corroded harness or transmission pass-through connector Most likely
- Converter clutch solenoid coil open Possible
- Internal transmission harness or mechatronic unit Possible
- Driver stage in the module faulty Less likely
- FCA: actual converter slip (clutch wear, fluid) or software Less likely
How to diagnose P0740
- Inspect the transmission harness and the connector where it enters the case for corrosion or fluid leaking into it.
- Measure the lock-up solenoid's resistance through the connector and compare it with the manual.
- If the wiring is fine and the solenoid is open, replace the solenoid. On many transmissions it's inside, behind the pan.
- Check for software updates for the transmission module.
Vehicles that report P0740 most
| Vehicle | Years | Reports | Share | Median miles |
|---|---|---|---|---|
| Honda Odyssey | 1998–2004 | 50 | 107k | |
| Honda Civic | 1999–2001 | 20 | 92k | |
| Honda Accord | 1997–2002 | 18 | 120k | |
| Acura TL | 2000–2003 | 5 | 74k | |
| Honda Pilot | 2003–2004 | 4 | 122k | |
| Dodge Grand Caravan | 2011–2015 | 3 | — |
Counts of owner complaints to the NHTSA that mention P0740 (120 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 7
- Transmission
- 40
- Specific fault
Questions drivers ask
Can I drive with code P0740?
Yes, gently. Get it checked soon, because the transmission runs hotter without lock-up.
Will my car pass an emissions inspection with P0740?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Will P0740 clear by itself?
The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.
Often reported together
Codes that owners mention in the same NHTSA complaints as P0740. They can point to a shared cause, so it's worth checking them together.
- P0730Incorrect Gear Ratio12 complaints
- P0700Transmission Control System (MIL Request)7 complaints
- P0758Shift Solenoid B Electrical3 complaints
- P0785Shift Timing Solenoid A3 complaints
- P1860Manufacturer-specific code3 complaints
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.