Circuit Description
The Torque Converter Clutch Solenoid Valve (TCC Sol. Valve) is a pulse width modulated solenoid. When vehicle operating conditions are appropriate for TCC application, the Powertrain Control Module (PCM) begins the TCC duty cycle at approximately 42%. The PCM then increases the duty cycle up to 90%, in order to achieve full TCC-apply pressure.
When the TCC Sol. Valve is de-energized, the solenoid blocks filtered 2-3 drive fluid, and allows TCC signal fluid to exhaust. When energized, the solenoid modulates fluid into the TCC signal fluid circuit. When fully energized, modulation stops, and the solenoid blocks both 2-3 drive fluid and TCC signal fluid exhaust.
The Torque Converter Clutch (TCC) release switch is part of the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Val. Position Sw.). The TFP Val. Position Sw. is mounted to the transmission valve body.
The TCC release switch is a normally-closed switch. The switch signals the Powertrain Control Module (PCM) that the TCC is released. Torque Converter release fluid pressure acts on the switch contact, opening circuit 657/1804. When the voltage on the circuit is high, the PCM recognizes that the TCC is no longer engaged.
When the PCM detects that the TCC release switch is closed when the TCC is commanded OFF, then DTC P0742 sets. DTC P0742 is a type A DTC.
Conditions for Setting the DTC
| • | No TP DTCs P0121, P0122 or P0123. |
| • | No TCC Release Sw. DTC P1887 |
| • | The engine is running. |
| • | The TP is greater than 12%. |
| • | The TCC is commanded OFF. |
| • | The time since the gear select lever change is greater than 6 seconds. |
| • | All of the above conditions are met for 8 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the Malfunction Indicator Lamp (MIL). |
| • | The PCM freezes shift adapts from being updated. |
| • | The PCM commands the TCC ON. |
| • | DTC P0742 is stored in the PCM history. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the MIL after three consecutive trips without a failure reported. |
| • | A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported. |
| • | 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
| • | Rapid fluctuation in line pressure could set DTC P0742. |
| • | Inspect for a pressure regulator problem. |
| • | Inspect for abnormal high or low line pressure. |
| • | Inspect the wiring for poor electrical connections at the PCM, the transmission 20-way connector and the TFP Val. Position Sw. 6-way connector for the following conditions: |
| - | A bent terminal |
| - | A backed out terminal |
| - | A damaged terminal |
| - | Poor 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. |
| • | The customer may notice an engine stalling condition. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for a TCC release switch status change when the engine is running. If TCC release oil is present, the switch should be open.
-
If you disconnect the transmission connector, the PCM should recognize an open TCC release switch. This indicates the wiring from the transmission connector to the PCM is OK.
-
This step ensures that the TCC release switch is in good working condition.
-
This step tests the TCC circuit for a mechanical or hydraulic condition.
Step | Action | Value(s) | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||||||||
2 |
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. Using the Clear Info function will erase the stored Freeze Frame and Failure Records from the PCM. Does the scan tool indicate TCC release pressure is present? | -- | Go to Diagnostic Aids | |||||||||||||
Start the engine. Does the scan tool indicate TCC release pressure is present? | -- | |||||||||||||||
Does the scan tool indicate TCC release pressure is present? | -- | |||||||||||||||
5 | Inspect circuit 657 for a short to ground. Refer to General Electrical Diagnosis . Did you find and correct the condition? | -- | ||||||||||||||
6 | Inspect circuit 1804 from the transmission 20-way connector to the TFP Val. Position Sw. for a short to ground. Refer to General Electrical Diagnosis . Did you find the condition? | -- | ||||||||||||||
Did you find the condition? | -- | |||||||||||||||
8 | Replace the TFP Val. Position Sw. Refer to the Transmission Unit Repair Manual, 4T40-E Section. Is the replacement complete? | -- | -- | |||||||||||||
Inspect and repair as necessary the following items:
Refer to the Transmission Unit Repair Manual, 4T40-E Section. Is the inspection and repair complete? | -- | -- | ||||||||||||||
10 | Replace the automatic transmission wiring harness. Refer to the Transmission Unit Repair Manual, 4T40-E Section. Is replacement complete? | -- | -- | |||||||||||||
11 | Replace the PCM. Refer to PCM Replacement/Programming . Is the replacement complete? | -- | -- | |||||||||||||
12 | In order to verify your repair, perform the following procedure:
Has the test run and passed? | -- | System OK |
