P0740

Code P0740, Torque Converter Clutch (TCC) Problem:

Torque Converter Clutch (TCC) Circuit:

CIRCUIT DESCRIPTION
The purpose of the Torque Converter Clutch (TCC) feature is to eliminate the power loss of the torque converter when the vehicle is in a cruise condition. This allows the convenience of the automatic and the fuel economy of a manual transaxle. The heart of the system are two PCM controlled solenoids located inside the transaxle.

When the TCC apply solenoid coil is activated ("ON"), the TCC engages, which results in a straight through mechanical coupling from the engine to the wheels. When the apply solenoid coil is deactivated ("OFF"), the TCC is released which allows the torque converter to operate in the conventional manner (fluid coupling between engine and transaxle).

The TCC PWM solenoid is used to vary hydraulic pressure to the converter clutch regulator valve, allowing a smoother engagement of the converter clutch.

DTC P0740 WILL SET WHEN:
^ Vehicle is in 3rd or 4th gear.
^ TCC is commanded "ON" by the PCM.
^ Engine RPM/vehicle speed ratio indicates TCC is not locked.
^ Throttle angle is greater than 10%.
^ Above conditions for over 10 seconds.

ACTION TAKEN (PCM will default to):
With a current DTC P0740 set, the PCM will not allow 4th gear operation. DTC P0740 does not illuminate the MIL (Service Engine Soon).

TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Determines whether fault is caused by a bad solenoid or control circuit.
2. Checks availability of B+ on CKT 241.
3. Checks the PCM's ability to pulse the PWM solenoid "ON" and "OFF."
4. Electrical circuits have checked out. If there is a TCC engagement problem.

DIAGNOSTIC AIDS
The Tech-1 only indicates when the PCM has commanded the TCC driver "ON"; this does not confirm that the TCC is actually engaged. To determine if TCC is functioning properly, road test the vehicle. Engine RPM should decrease when the Tech-1 indicates the TCC has been turned "ON." If diagnosis indicates that all electrical circuits and components are OK, there may be a hydraulic or mechanical problem in the transaxle.