P0740

Circuit Description

The torque converter clutch (TCC) solenoid valve is an ON/OFF (normally OFF) valve which controls the converter clutch apply and release. The torque converter clutch pulse width modulation (TCC PWM) solenoid valve works with the TCC solenoid valve to control the clutch apply rate (feel). The PCM controls the duty cycle on the TCC PWM solenoid valve to regulate the feed pressure to the converter clutch regulator valve, which in turn, regulates the converter clutch apply pressure.

The TCC solenoid valve receives ignition voltage from circuit 1039. The PCM controls the ground path on circuit 422 to turn the solenoid on and off. The PCM uses throttle position, vehicle speed and other inputs in order to determine when to energize the solenoid. When the solenoid is OFF, the PCM will receive a high (ignition voltage) signal. When the solenoid is ON, the PCM will receive a zero voltage signal.

When the PCM detects a continuous open or short in the TCC solenoid valve circuit, then DTC P0740 sets. DTC P0740 is a type B DTC.

Conditions for Running the DTC

^ System voltage is 10-18 volts.
^ The engine speed is greater than 500 RPM for 5 seconds.
^ Not in fuel shut off.

Conditions for Setting the DTC

DTC P0740 sets if one of the following conditions exists for 5 seconds:

Condition 1
The PCM commands the solenoid ON, and the voltage signal to the PCM remains high (B+).

Condition 2
The PCM commands the solenoid OFF, and the voltage signal to the PCM remains low (0 volts).

Action Taken When the DTC Sets

^ The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the conditions for setting the DTC exist.
^ The PCM inhibits TCC.
^ The PCM inhibits 4th gear, if the transmission is in hot mode.

Conditions for Clearing the MIL/DTC

^ The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
^ A scan tool clears the DTC from PCM history.
^ The PCM clears the DTC from the PCM history if the vehicle completes 40 consecutive warm-up cycles without an emission related diagnostic fault occurring.
^ The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM.

Diagnostic Aids

^ Inspect the wiring at the PCM, the transmission connector, TCC enable solenoid connector and all other circuit connecting points for the following conditions:
- A backed out terminal
- A damaged terminal
- Reduced terminal tension
- A chafed wire
- A broken wire inside the insulation
- Moisture intrusion
- Corrosion
^ When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

6. This step isolates the fault between the engine harness and the transmission harness.
8. This step checks if engine harness circuit 422 is open.
11. This step checks if the solenoid and transmission wiring is within resistance specifications.