P0740
Torque Converter Clutch Circuit/Open
- Severity
- Medium
- Driving
- Drivable — book it in
The torque converter clutch circuit has an open circuit or a general electrical fault. The torque converter clutch is what locks the engine directly to the transmission at cruising speed, removing the slight slip that a torque converter otherwise has. When it cannot be controlled, the car drives normally but uses noticeably more fuel and the engine sits at higher revs on the motorway.
Possible causes
- CommonFailed torque converter clutch solenoid
- CommonWiring or connector fault at the transmission case connector
- CommonFluid wicking into the connector and corroding pins
- PossibleInternal transmission harness failure
- PossibleLow or degraded fluid
- RareFailed transmission control module driver
What you might notice
- Higher engine speed at a steady motorway cruise than usual
- Noticeably worse fuel consumption
- No lock-up feel - the slight drop in revs at cruise never happens
- Check engine light on
- Transmission running hotter
What to check, in order
- Check the fluid level and condition first.
- Watch the torque converter clutch slip and lock-up status on the live data screen at a steady cruise.
- Inspect the transmission case connector for fluid and corrosion.
- Measure the solenoid winding resistance against specification if it can be reached.
- Expect the solenoid to be inside the transmission on most vehicles - the repair means dropping the pan, so confirm the diagnosis before starting.
- A converter clutch that never locks makes the transmission run hotter, which shortens fluid life. Worth fixing even though nothing feels wrong.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Transmission
P0700P0701P0702P0703P0704P0705P0706P0707P0708P0709P0710P0711P0712P0713P0714P0715P0716P0717P0718P0719P0720P0721P0722P0723P0724P0725P0726P0727P0728P0729P0730P0731P0732P0733P0734P0735P0736P0737P0738P0739P0740P0741P0742P0743P0744P0745P0746P0747P0748P0749P0750P0751P0752P0753P0754P0755P0756P0757P0758P0759P0760P0761P0762P0763P0764P0765P0766P0767P0768P0769P0770P0771P0772P0773P0774P0775P0776P0777P0778P0779P0780P0781P0782P0783P0784P0785P0786P0787P0788P0789P0790P0791P0792P0793P0794P0795P0796P0797P0798P0799