CIRCUIT DESCRIPTION:
LRTP protects the transmission during low vehicle speed conditions. When an engine torque rating exceeds a predetermined value, LRTP limits engine torque in lower ranges to protect the transmission from damage during a converter stall condition. DTC P2641 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 Control Module (ECM) is not responding to the LRTP torque reduction signal request from the TCM.
2. A non-approved J1939 device is interfering with the LRTP torque reduction signal request.

ACTION TAKEN WHEN THE DTC SETS:
When DTC P2641 is active, the following conditions occur:
1. The CHECK TRANS light illuminates (non-OBD II strategy).
2. The TCM forces Variable Modulated Main off.
3. Calibration dependent, send default torque message or stop broadcast of J1939/71 ETC1.
4. The DTC is stored in the TCM history.

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. Poor engine performance can allow this code to set. Have the OEM inspect for possible exhaust manifold pressure sensor concern or other engine related subsystems.
2. There may be no output broadcast to the speedometer when this code is active.
3. If DTC P0614 is set in combination with DTC P2637 and/or DTC P2641, engine control software is not correct. Verify the proper software is installed.