Circuit Description
The transmission control module (TCM) sends an output duty cycle signal which activates the lock-up solenoid . This signal is used to control torque converter lock-up piston inside the torque converter.
DTC Descriptor
This diagnostic procedure supports the following DTC: DTC P0740 Torque Converter Clutch (TCC) Electrical Circuit
Conditions for Setting the DTC
When the transmission control module (TCM) sends an output duty cycle signal to activate the lock-up solenoid, but the return signal is received as OFF by the monitoring signal.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate. |
| • | When the TCM detects failures on two consecutive driving cycles. |
| • | Lock-up control is inhibited and the solenoid is turned off. |
Conditions for Clearing the MIL/DTC
| • | The TCM stops sending MIL request to the ECM when no further failures are detected after 3 consecutive driving cycles and the ECM turns off the MIL on the next driving cycle (MIL off at the 4th driving cycle). |
| • | A history DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | Clear the DTCs with a scan tool. |
Diagnostic Aids
When DTC P0740 sets, the possible cause of the fault could be:
| • | Open or short circuit in the wiring harness and/or connector |
| • | Lock-up malfunction |
| • | Faulty TCM |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Automatic Transmission? | -- | Go to Step 2 | |
2 |
Is the resistance in the specified range? | 13 ohms 20°C (70°F) | Go to Step 3 | Go to Step 5 |
3 | Perform a continuity check between the lock-up solenoid connector terminal 4 and the TCM connector Terminal 3. Is there continuity? | Go to Step 4 | Go to Step 5 | |
4 | Replace the Lock-up solenoid. Does the lock-up solenoid operate correctly? | -- | Go to Step 7 | Go to Step 6 |
5 | Repair the wiring harness as necessary. Refer to Wiring Repairs . Is the action complete? | -- | Go to Step 7 | -- |
6 | Replace the TCM. Refer to Transmission Control Module Replacement . Is the action complete? | -- | Go to Step 7 | -- |
7 |
Did the last test fail or is the current DTC displayed? | -- | Go to Step 2 | System OK |
