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
* If the TCC slip speed does not decrease when TCC is commanded ON, the TCC solenoid or valves in the valve body or transmission fluid pump cover are suspect.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics Electrical Diagrams
Connector End View Reference
* Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
* Inline Harness Connector End Views X100
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. Verify the transmission fluid level is correct, refer to Transmission Fluid Level and Condition Check Testing and Inspection.
2. Drive vehicle until the scan tool Trans. Fluid Temp. is 74°C (165°F) or greater.
3. Command the TCC Control Solenoid OFF with a scan tool.
4. Verify the scan tool TCC Slip Speed parameter increases to 20 RPM or greater during vehicle acceleration and the TCC PC Sol. Command is 40 kPa (5 psi) or less.
• If TCC Slip Speed is less than 20 RPM
Refer to Circuit/System Testing
• If TCC Slip Speed is 20 RPM or greater
5. Verify the scan tool TCC Slip Speed is -20 RPM or lower during vehicle deceleration and the TCC PC Sol. Command is 40 kPa (5 psi) or less.
• If TCC Slip Speed is greater than -20 RPM
Refer to Circuit/System Testing
• If TCC Slip Speed is -20 RPM or lower
6. Exit scan tool TCC Control Solenoid command, Tow/Haul Mode ON, selector in the M position and Manual Mode set to 3.
7. Verify the scan tool TCC Slip Speed parameter is less than 80 RPM during heavy acceleration with transmission in 3rd gear and a TCC PC Sol. Pressure Command of 1000 kPa (145 psi) or greater.
• If TCC slip speed is 80 RPM or greater
Refer to Circuit/System Testing
• If TCC slip speed is less than 80 RPM
8. Verify the scan tool TCC Slip Speed parameter is between -20 to +20 RPM during light acceleration and closed throttle deceleration with a TCC PC Sol. Pressure Command of 1000 kPa (145 psi) or greater.
• If TCC slip speed is not between -20 to +20 RPM
Refer to Circuit/System Testing
• If TCC slip speed is between -20 to +20 RPM
9. 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.
10. Verify the DTC does not set.
• If the DTC sets
Refer to Circuit/System Testing
• If the DTC does not set
11. All OK.
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. Verify line pressure is correct, 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.
• If line pressure is correct
2. Listed are conditions for each component that could set DTCs P0741 or P0742:
* Q39A Torque Converter Clutch Pressure Control Solenoid Valve stuck ON or OFF.
* TCC PCS Valve stuck/sticking - debris, binding, damaged valve, or scored bore.
* Separator plate orifices blocked by debris.
* TCC Valve stuck/sticking - debris, binding, damaged valve, or scored bore.
* Torque Converter internal damage - worn torque converter clutch
* Incorrect torque converter bolts - too long
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Control Valve Solenoid Replacement (PCS1 and PCS2) Control Valve Solenoid Replacement (PCS1 and PCS2)Control Valve Solenoid Replacement (SS1, SS2, SS3, TCC, and MAIN MOD) Control Valve Solenoid Replacement (SS1, SS2, SS3, TCC, and MAIN MOD)
* 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.