Allison 1000 & 2000 Gen 4 Fault Codes: P0741 Torque Converter Clutch System Stuck Off

CIRCUIT DESCRIPTION:
The Transmission Control Module (TCM) uses data 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. DTC P0122, P0123, P0716, P0717, P0721, P0722, or P0743 (previously P1860) is not active.
2. The components are powered and ignition voltage is greater than 9V and less than 18V (12V TCM) or greater than 18V and less than 32V (24V TCM).
3. Engine speed is greater than 200 rpm for 5 seconds.
4. Transmission is in a valid forward range.
5. Throttle position is over 1 O percent but less than 90 percent.
6. Six seconds or more have expired since TCC was applied in a range.

CONDITIONS FOR SETTING THE DTC:
DTC P0741 sets when the TCM detects a torque converter clutch slip value greater than 80 rpm for more than 15 seconds, indicating no TCC apply.

ACTION TAKEN WHEN THE DTC SETS:
1. DTC P0741 is stored in the TCM history.
2. The CHECK TRANS light illuminates on the second occurrence.
3. The TCM freezes shift adapts (DNA).

CONDITIONS FOR CLEARING THE DTC/CHECK TRANS LIGHT:
A Scan Tool may be used to clear the code 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:
Residue or contamination may cause shift valves to stick intermittently.