P0740

DTC P0740 Torque Converter Clutch (TCC) Problem:

Transmission Controls' Wiring Schematic:

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 Powertrain Control Module (PCM) controlled solenoids located inside the transaxle.

When the TCC apply solenoid coil is activated "ON", the TCC is applied, 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 (fluidic coupling between engine and transaxle).

The Torque Converter Clutch Pulse Width Modulated (TCC PWM) solenoid is used to vary hydraulic pressure to the converter clutch regulator valve, allowing a smoother engagement of the converter clutch.


DIAGNOSTIC TROUBLE CODE (DTC) PO74O 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 Malfunction Indicator Lamp (MIL).

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Determines whether fault is caused by a faulty solenoid or control circuit.
2. Checks availability of positive battery voltage on CKT 241.
3. Checks the PCM's ability to pulse the PWM solenoid "ON" and "OFF".
4. Electrical circuits have checked out.

DIAGNOSTIC AIDS
The Tech 1 scan tool 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 scanner indicates the TCC has been turned "ON." If diagnosis indicates that all electrical circuits and components are OK, refer to Automatic Transaxle Diagnosis.