Allison 1000 & 2000 Gen 4 Fault Codes: P2773 Torque Control Request Ignored – ECM/TCM

Allison 1000 & 2000 Gen 4 Fault Codes: P2773 Torque Control Request Ignored – ECM/TCM

CIRCUIT DESCRIPTION:
Shift Energy Management (SEM) allows the Transmission Control Module (TCM) to request torque reduction from the engine controller. By reducing torque during upshifts, shifts can be made quicker and at a more consistent output torque. This increases clutch life by reducing clutch engagement temperatures.

CONDITIONS FOR RUNNING THE DTC:
1. DTC U2105 CAN bus error is not active.
2. The components are powered and ignition voltage is greater than 9V and less than 18V (12V TCM) or greater 18V and less than 32V (24V TCM).
3. Engine speed is greater than 200 rpm but less than 7500 rpm for 5 seconds.
4. SEM has been activated for this vehicle.

CONDITIONS FOR SETTING THE DTC:
DTC P2773 sets when the TCM detects one of the following conditions for a minimum of four upshifts (consecutive or nonconsecutive) during one drive cycle:
1. Engine ECM is not responding to torque reduction signal request from the TCM.
2. A nonapproved J 1939 device is interfering with the torque reduction signal request.

ACTION TAKEN WHEN THE DTC SETS:
1. The CHECK TRANS light illuminates.
2. All 4-5 upshifts and full throttle 3-4 upshifts are inhibited.

CONDITIONS FOR CLEARING THE DTC/CHECK TRANS LIGHT:
A Scan Tool may be used to clear the code from the TCM history. The DTC is cleared if, for one ignition cycle, actual engine torque follows TCM commanded torque for 20 consecutive upshifts. To be counted as one upshift, engine torque demand must be above 80 N-m (59 lb ft).

DIAGNOSTIC AIDS:
1. It will be necessary to drive the vehicle with heavy to moderate throttle settings for at least four upshift cycles in order to set a DTC P2773.
2. If DTC P2773 becomes active shortly AFTER an engine update and the troubleshooting procedure for P2773 has been performed, see TCM Parameters to Support Engine information.