Allison 1000 & 2000 Gen 5 Fault Code:P0741 Torque Converter Clutch (TCC) System – Stuck Off

CIRCUIT DESCRIPTION:
The transmission TCC solenoid is a pressure control solenoid used to control the rate of TCC apply and release. The TCM applies and releases the TCC by varying the amount of electrical current through a low side driver. The TCM uses data received from the engine speed sensor and the turbine speed sensor to calculate torque converter slip values. It can detect if the torque converter is stuck off (unlocked) or stuck on (locked) by comparing TCC slip speed to a preset value in the TCM calibration. The DTC P0741 sets when the TCM detects a slip speed exceeding a calibrated rpm for calibrated amount of time, indicating no TCC apply.

ACTION TAKEN WHEN THE DTC SETS:
1. DTC P0741 is stored in the TCM history.
2. The TCM forces Variable Modulated Main off.
3. The CHECK TRANS light illuminates.

CONDITIONS FOR CLEARING THE DTC:
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:
1. This DTC sets when converter slip speed indicates TCC is not applied when the TCC solenoid is commanded ON for a period of time that is calibration dependent. This may indicate an internal failure of the TCC or a stuck or sticking TCC valve.
2. Residue or contamination may cause shift valves to stick intermittently.
3. This concern may indicate a torque converter flow valve that is stuck or sticking.