6T70/6T75 - 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) - Stuck Off
DTC P0742
- Torque Converter Clutch (TCC) - Stuck On
Circuit/System Description
The torque converter clutch (TCC) pressure control (PC) solenoid is part of the control solenoid valve assembly which has no serviceable components. The TCC PC solenoid is a normally low pressure control solenoid. The TCC PC solenoid regulates transmission fluid to the TCC regulator valve in the lower valve body and the TCC control valve in the pump cover. When vehicle operating conditions are appropriate to apply the converter clutch, the transmission control module (TCM) will increase TCC PC current flow, duty cycle, to the TCC solenoid. The TCC PC solenoid directs fluid pressure to move the TCC control valve to the apply position, and moves the TCC regulator apply valve to the regulating position. The TCC regulator valve regulates TCC apply fluid pressure proportional to TCC solenoid pressure. When the TCC is fully applied, the engine is coupled directly to the transmission. TCC release is accomplished by the TCM decreasing current flow to the TCC PC solenoid. This results in decreasing the apply pressure which allows the TCC control valve to move to the release position. The TCM calculates torque converter slip speed based on engine speed and transmission input shaft speed.
Conditions for Running the DTC
P0741
* No DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, P0742, P2763, or P2764.
* The engine speed is greater than 400 RPM for 5.0 seconds.
* The ignition voltage is greater than 8.6 volts.
* The transmission fluid temperature (TFT) is 20-130°C (68-266°F).
* The throttle position is greater than 8 percent.
* The engine torque is greater than 50 Nm (36 lb ft).
* The 2nd gear ratio is between 2.67-3.07.
* The 3rd gear ratio is between 1.71-1.97.
* The 4th gear ratio is between 1.32-1.51.
* The 5th gear is between 0.93-1.07.
* The 6th gear is between 0.69-0.79.
* The TCC is commanded ON.
* The engine torque signal is valid.
* The throttle position signal is valid.
P0742
* No DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0401, P042E, P0716, P0717, P0722, P0723, P0741, P2763, or P2764.
* The commanded range is 2nd gear or higher.
* The ignition voltage is greater than 8.6 volts.
* The TFT is 20-130°C (68-266°F).
* The calc. throttle position is greater than 8 percent.
* The engine torque is greater than 80 Nm (59 lb ft).
* The engine speed is greater than 500 RPM.
* The vehicle speed is greater than 16 km/h (10 mph).
* The gear ratio is between 0.69-3.07.
* The engine torque signal is valid.
* The throttle position signal is valid.
* The TCC is commanded OFF.
Conditions for Setting the DTC
P0741
* The TCC Pressure command is greater than 500 kPa (73 psi) for 2 seconds.
* The TCM detects TCC slip greater than 50 RPM for 4 seconds when the TCC is commanded ON. This must occur 3 times.
P0742
The TCM detects the TCC slip between -20 and +30 RPM for 2.5 seconds or greater when the TCC is commanded OFF. This must occur 6 times.
Action Taken When the DTC Sets
P0741
* DTC P0741 is a Type B DTC.
* The TCM inhibits high gear.
* The TCM inhibits TCC.
* The TCM forces hot mode shift pattern.
P0742
* DTC P0742 is a Type A DTC.
* The TCM freezes transmission adaptive functions.
* The TCM forces hot mode shift pattern.
Conditions for Clearing the DIC/DTC
P0741
DTC P0741 is a Type B DTC.
P0742
DTC P0742 is a Type A DTC.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics (6T70/6T75 - Automatic Transmission)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Transmission General Description (Transmission General 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 (Programming and Relearning) 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. Engine idling in Park, verify with a scan tool the Transmission ISS/OSS Supply Voltage parameter displays OK.
3. Engine idling in Park. Observe the Transmission ISS parameter on the scan tool, while varying the engine speed. The Transmission ISS parameter should vary with engine speed and not drop out.
4. Operate the vehicle at 16-32 km/h (10-20 mph) while observing the Transmission OSS parameter on the scan tool. The Transmission OSS parameter should vary with the vehicle speed and not drop out.
Note: Perform a scan tool snapshot, during the road test.
5. Perform the Road Test (6T70/6T75 - Automatic Transmission). Verify the transmission operation performs as indicated, in the road test instructions.
6. Review the scan tool snapshot transmission data parameters. Verify the engine and transmission data parameters display the correct values in all forward gear ranges:
* Engine Speed
* ECT
* Transmission ISS
* Transmission OSS
* Vehicle Speed
* Trans. Fluid Temp.
* TCC PC Sol. Pressure Command
* TCC Slip Speed
7. 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 from the Freeze Frame/Failure Records data.
Circuit/System Testing
1. Perform the Line Pressure Check (Line Pressure Check). Verify the transmission line pressures are within the specified ranges.
• If not within the specified ranges, refer to Fluid Pressure High or Low (Fluid Pressure High or Low).
2. Ignition OFF, remove the control solenoid valve assembly. Refer to Control Solenoid Valve and Transmission Control Module Assembly Replacement (6T70/6T75 - Automatic Transmission).
3. Perform the Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test (Control Solenoid Valve and Transmission Control Module Assembly Solenoid Performance Test). Test all solenoids on the control solenoid valve assembly. A pressure change should occur for each solenoid.
• If the control solenoid valve assembly does not pass the performance test, replace the control solenoid valve assembly.
4. Listed in the table below are conditions for each component that could set DTC P0741 or P0742. Carefully inspect each component for that condition. Repair or replace as necessary.
Repair Instructions
Important:
* Perform the Service Fast Learn Adapts (6T70/6T75 - Automatic Transmission) following all transmission related repairs.
* Before replacing the TCM, perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection (Control Solenoid Valve and Transmission Control Module Assembly Inspection).
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Control Valve Lower Body and Upper Body Replacement (Control Valve Lower Body and Upper Body Replacement)
* Torque Converter Removal (2. Torque Converter Removal)
* Torque Converter Installation (63. Torque Converter Installation)
* Torque Converter and Differential Housing, Front Differential Transfer Drive Gear, and Front Differential Carrier Removal (9. Torque Converter and Differential Housing, Front Differential Transfer Drive Gear, and Front Differential Carrier Removal)and Torque Converter and Differential Housing Installation (33. Torque Converter and Differential Housing Installation)
* Control Module References (Programming and Relearning) for control solenoid valve assembly replacement, setup, and programming