Powertrain, generic · Transmission

P0740 Torque Converter Clutch Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

Open or corroded harness or transmission pass-through connector
Converter clutch solenoid coil open
Internal transmission harness or mechatronic unit
Driver stage in the module faulty
FCA: actual converter slip (clutch wear, fluid) or software

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

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–900
Time1–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

What to check first

  1. Check solenoid circuit
  2. Inspect connector

Parts involved

torque converter clutch solenoidtorque convertertransmission valve bodytransmission control module

Related codes

P0741P0742P0743P0744P2763P2764

References: newtonnet.co.uk, fordservicecontent.com, gsi.ext.gm.com, static.nhtsa.gov.