Allison 3000 & 4000 Gen 4 Fault Code: P0741 Torque Converter Clutch (TCC) System Stuck Off

DIAGNOSTIC RESPONSE:
None

CIRCUIT DESCRIPTION:
The Transmission Control Module (TCM) uses data received from the engine speed sensor and the turbine speed sensor to calculate torque converter slip value. The TCM then compares this calculated slip value to a preset value in the TCM calibration.

CONDITIONS FOR RUNNING THE DTC:
1. Hydraulic system is pressurized.
2. Hydraulic default condition not present.
3. Engine initialization or shutdown is not in process.
4. Selected range is a forward range.
5. Throttle position is 50% or more.
6. Transmission fluid temperature is between 25°C (77°F) and 130°C (266°F).
7. Six or more seconds have elapsed since Torque Converter Clutch (TCC) was applied in a range.

CONDITIONS FOR SETTING THE DTC:
DTC P0741 sets when the TCM detects a TCC slip value greater than 150 rpm for more than 15 seconds, indicating TCC did not apply.

ACTION TAKEN WHEN THE DTC SETS:
1. DTC is stored in TCM history.
2. The CHECK TRANS light illuminates.
3. TCC (lockup clutch) commanded off.

CONDITIONS FOR CLEARING THE DTC/CHECK TRANS LIGHT:
Use the diagnostic tool to clear the DTC from the TCM history. The TCM automatically clears the DTC from the TCM history if the vehicle completes 40 warm-up cycles without the DTC recurring.

DIAGNOSTIC AIDS:
DTC PO741 may be caused by:
1 Turbine speed sensor signal circuit issues.
2. Low TCC pressure and/or main pressure.
3. Control module issues like stuck/sticky valves, mechanically defective TCC solenoid, broken springs, damaged valve bores, plugged suction filter, damaged gaskets, excessive leaks to exhaust, etc.
4. Transmission issues such as worn and/or damaged seals or seal rings, worn TCC damper, mechanical TCC issues, rotating drum damage (affecting turbine speed pickup), debris, excessive hydraulic circuit leaks to exhaust or other hydraulic circuits.
5. Issue with TCM.