What this code means
P0740 may indicate an electrical open in the torque converter clutch solenoid circuit on the 10R140 transmission.
What the vehicle may do
- The converter clutch may stay released.
- The transmission can default to high line pressure when solenoid power is removed.
- The driver may notice transmission behavior that feels abnormal or firm.
Possible fault areas
- Possible connector terminal damage, corrosion, loose wiring, or seal issues.
- Possible TCC solenoid concern.
- Possible internal transmission harness concern.
- Possible TCM-related concern.
Diagnostic path
P0740 overview
On a 2011 through 2025 Ford F-250 Super Duty with the 6.7 Power Stroke and 10R140 transmission, P0740 means the transmission control side may be seeing an open circuit in the torque converter clutch solenoid circuit. The truck may keep the converter clutch released, and when power is removed from this shared solenoid power feed, line pressure can default high. So the broad areas to keep in mind are connector condition, vehicle wiring, the internal transmission harness, the TCC solenoid itself, and the TCM. For this code, stay focused on the TCC side of the circuit, not the other solenoid circuits that may use the same test path.
Start with the shared power feed
Begin with the ignition off. Disconnect transmission vehicle harness connector C168A and inspect it closely for damaged or pushed-out terminals, corrosion, loose wires, and missing or damaged seals. The important caution here is that the PCM can remove power from the Transmission Solenoid Power Control circuit when certain electrical faults are present. Have the meter connected before turning the ignition on, and use min-max or recording so you catch the voltage before it drops out. Connect the meter from C168A Pin 11 to ground, turn the ignition on, and check the maximum recorded voltage. If it is greater than 11 volts, move on to the TCC solenoid control circuit checks. If it is not greater than 11 volts, keep diagnosing the TSPC2 feed circuit.
If the feed voltage is missing
With the ignition off, disconnect TCM connector C1750 and inspect that connector the same way: damaged or pushed-out terminals, corrosion, loose wires, and seal damage. Measure between C1750 Pin 12 and C168A Pin 11. You want less than 3 ohms. If that is not there, repair the circuit. If continuity is good, check C1750 Pin 12 to ground. That reading should be greater than 10,000 ohms. If it is not, repair the circuit. If the feed circuit has continuity and is not shorted to ground, the next supported action is to install a new TCM and carry out the transmission strategy download.
Check the external TCC control circuit
If the TSPC2 feed voltage was present, move to the TCC solenoid control circuit. With the ignition off and TCM C1750 disconnected, measure from C1750 Pin 5 to C168A Pin 25. The TCC control circuit should be less than 3 ohms. If it is not, repair that circuit. Next, check C1750 Pin 5 to ground. That should be greater than 10,000 ohms. If it is not, repair the circuit. Then check the TCC control circuit for a short to the transmission power circuits by measuring C1750 Pin 5 to C1750 Pin 1, Pin 2, Pin 12, Pin 20, Pin 26, Pin 27, Pin 34, Pin 47, and Pin 48. Those readings should be greater than 10,000 ohms. If any are not, repair the circuit before going farther.
Check the internal transmission harness
Once the external wiring checks pass, go inside the transmission circuit path. With the ignition off, drain the transmission fluid and remove the transmission fluid pan. Disconnect TCC solenoid connector C1841. For the TCC circuit, measure from the transmission component side Pin 11 to C1841 Pin 1, and from the transmission component side Pin 25 to C1841 Pin 2. Both readings should be less than 3 ohms. If they are not, install a new transmission internal wiring harness, both pieces. If the opens check passes, check the same internal circuits for a short to ground: transmission component side Pin 11 to ground, and transmission component side Pin 25 to ground. Both should be greater than 10,000 ohms. If they are not, install a new transmission internal wiring harness, both pieces.
Check the TCC solenoid
Now measure and record the resistance of the TCC solenoid itself. The TCC solenoid specification is 4.6 to 5.2 Ohms. The shared chart also lists LPC solenoid 4.6 to 5.2 Ohms, but for P0740 the diagnostic decision stays on the TCC solenoid circuit. If the TCC solenoid is outside its range, install a new solenoid for the solenoid that failed the resistance check. If the resistance is in range, check for a short to ground by measuring between either pin of the TCC solenoid and ground. That reading should be greater than 10,000 ohms. If it is not, install a new solenoid.
Reconnect the transmission path and confirm power at the solenoid
If the solenoid checks pass, connect transmission vehicle harness C168A. For the TCC circuit, measure from C1841 Pin 2 to C1750 Pin 5. That resistance should be less than 3 ohms. If it is not, treat it as a terminal fitment issue and repair the vehicle wiring harness. If that passes, connect TCM C1750, turn the ignition on, and measure C1841 Pin 1 to ground. The voltage should be greater than 11 volts on the TCC circuit. If it is not, again treat it as a terminal fitment issue and repair the vehicle wiring harness.
Verify the repair
When the final voltage check passes, connect all electrical connectors, clear the code, and run the KOEO and KOER self-tests. If P0740 returns after the circuit checks have passed, the supported next step is to install a new TCM and carry out the transmission strategy download. If the code does not return, the fault is no longer present and may have been caused by a terminal fitment issue.
Takeaway
The clean diagnostic path for P0740 is to prove the TSPC2 power feed first, then the external TCC control circuit, then the internal harness, then the TCC solenoid, and finally the connected circuit under power. Do not guess at the solenoid or the module until the wiring path has earned that decision. For more diagnostic training, visit stepdiagnostics.com.
Final check
P0740 is best approached as a circuit diagnosis first, with the TCC power feed, control circuit, internal harness, solenoid, and TCM decision checked in order.
For more guided automotive diagnostics, visit STEP Diagnostics.
