Allison - Automatic Transmission

DTC P0741 or P0742

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

DTC Descriptors
DTC P0741
- Torque Converter Clutch (TCC) System-Stuck Off

DTC P0742
- Torque Converter Clutch (TCC) System-Stuck On

Circuit/System Description

The torque converter clutch (TCC) solenoid is used to control the rate of TCC apply and release. This solenoid is a pressure controlling solenoid that is controlled by the transmission control module (TCM). The TCM varies the amount of electrical current to the TCC solenoid by changing the solenoid duty cycle. Varying the solenoid's duty cycle modulates the amount of fluid pressure supplied to the converter clutch regulator valve. The regulator valve then modifies the TCC fluid pressure. The TCC will apply or release with the change in TCC fluid pressure. The TCM compares the transmission input speed with the transmission turbine speed to determine converter slip speed; transmission input speed minus transmission turbine speed.

Conditions for Running the DTC

P0741
* Engine speed is greater than 200 RPM for 5 seconds.
* Battery voltage is between 9-18 V.
* Transmission fluid temperature (TFT) is between 5-130°C (41-266°F).
* Transmission is in a forward range.
* Throttle position is between 10 percent and 90 percent.
* Six seconds or more since last range change.
* The TCC commanded pressure is 1000 kPa (145 psi) or greater.
* DTC P0716, P0717, P0721, P0722, P0741, P2761, P2763, or P2764 is not set.

P0742
* TCC is commanded off.
* TCC slip speed is between -20 and 20 RPM.
* Throttle position is greater than 25 percent.
* Engine speed is greater than 200 RPM for 5 seconds.
* Engine speed is 3500 RPM or less.
* Turbine speed is 3500 RPM or less.
* Output speed is 100 RPM or greater.
* Battery voltage is between 9-18 V.
* Engine torque is 175 Nm (129 lb ft) or greater.
* Transmission is in a forward range.
* DTC P0716, P0717, P0721, P0722, P2761, P2763, P2764 or U0100 is not set.
* Engine speed status is normal.

Conditions for Setting the DTC

P0741

The TCC is commanded on and the TCM detects converter slip than 80 RPM or greater for 15 seconds.

P0742 Condition 1 High Torque Condition

The TCC is commanded off and the throttle position is greater than 70 percent and net engine torque is greater than 275 Nm and the expected converter slip is not observed for 2 seconds.

P0742 Condition 2 High Acceleration Condition

The TCC is commanded off and the output shaft acceleration is greater than 100 RPM/second and the expected converter slip is not observed for 5 seconds.

P0742 Condition 3 Accel/Decel/Accel Condition

The TCC is commanded off and an output acceleration event is followed by an output deceleration event and followed by another output acceleration and the expected converter slip is not observed. An output acceleration event occurs when output shaft acceleration is greater than 40 RPM/second for 4 seconds or longer. An output deceleration event occurs when output shaft acceleration is -40 RPM/second for 2.5 seconds or longer.

Action Taken When the DTC Sets

P0741
* DTC P0741 is a Type B DTC.
* The TCM inhibits TCC.

P0742
* DTC P0742 is a Type B DTC.
* Reverse operation is disabled.

Conditions for Clearing the DTC

DTCs P0741 and P0742 are Type B DTCs.

Diagnostic Aids

* You must drive the vehicle in order to experience a condition.
* DTCs P0741 and P0742 may be caused by any of the following:

- An internal problem with the TCC
- A stuck or sticking TCC regulator valve
- A stuck or sticking TCC valve
- The TCC solenoid

Reference Information
Schematic Reference

Automatic Transmission Controls Schematics (Allison - Automatic Transmission)
Connector End View Reference

* Component Connector End Views (Connector End Views By Name)
* Inline Harness Connector End Views (Connector End Views By Number)

Description and Operation

* Transmission General Description (Transmission General Description)
* Transmission Component and System Description (Transmission Component and System Description)
* Electronic Component Description (Electronic Component Description)

Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference

Control Module References (Control Module References) for scan tool information

Circuit/System Verification

1. Perform the Transmission Fluid Level and Condition Check (Transmission Fluid Level and Condition Check) to verify correct fluid level and condition.
2. Perform a Road Test (Allison - Automatic Transmission).
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed on the Freeze Frame/Failure Records data.

Circuit/System Testing

Warning

Chock the wheels to prevent the vehicle from moving. Failure to chock the wheels can cause personal injury when the electrical system is repaired.

Note: You must perform the Circuit/System Verification first.

1. Perform a line pressure test. Refer to Line Pressure Check (Line Pressure Check).

• If line pressure is low in all ranges, refer to Low Main Line Pressure in All Ranges (Low Main Line Pressure in All Ranges).
• If line pressure is low in a specific range or ranges, refer to Low Main Line Pressure in Specific Ranges, Normal Pressure in Other Ranges (Low Main Line Pressure in Specific Ranges, Normal Pressure in Other Ranges).

2. Engine idling, shift selector in park, record line pressure. Use the scan tool to command the TCC Control Solenoid ON and verify the TCC PC Sol. Pressure Command parameter changed from 0 kPa (0 psi) to 1,600 kPa (232 psi). Record the line pressure after the pressure stabilizes. Line pressure should drop when the TCC Control Solenoid is commanded ON.

• If the pressure did not drop, refer to Control Valve Body Assembly Disassemble (83. Control Valve Body Assembly Disassemble) and Control Valve Body Cleaning and Inspection (84. Control Valve Body Cleaning and Inspection). If valve body inspection is normal, replace the TCC Solenoid. Refer to Control Valve Solenoid Replacement (SS1, SS2, SS3, TCC, and MAIN MOD) (Control Valve Solenoid Replacement (SS1, SS2, SS3, TCC, and MAIN MOD))Control Valve Solenoid Replacement (PCS1 and PCS2) (Control Valve Solenoid Replacement (PCS1 and PCS2)). If line pressure still does not drop, refer to Transmission Fluid Pump Cover Disassemble (31. Transmission Fluid Pump Cover Disassemble).

3. If the above tested normal, replace the torque converter. Refer to Torque Converter Replacement (Service and Repair).

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Control Valve Solenoid Replacement (SS1, SS2, SS3, TCC, and MAIN MOD) (Control Valve Solenoid Replacement (SS1, SS2, SS3, TCC, and MAIN MOD))Control Valve Solenoid Replacement (PCS1 and PCS2) (Control Valve Solenoid Replacement (PCS1 and PCS2))
* Torque Converter Replacement (Service and Repair)

Repair Verification

If another DTC is present, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle) and perform the appropriate diagnostic procedure.