Allison 1000 & 2000 Gen 5 Fault Code:P0634 TCM Internal Temperature Too High

CIRCUIT DESCRIPTION:
The TCM is equipped with an internal temperature sensor mounted directly to its circuit board. The TCM will take action to protect against damage from overheat.

ACTION TAKEN WHEN THE DTC SETS:
1. The TCM illuminates the CHECK TRANS light (non-OBD II strategy).
2. The TCM commands OFF all solenoids (SOLOFF).
3. The TCM forces Variable Modulated Main off.
4. The transmission will default to hydraulic state of Neutral, Reverse, 1st, 3rd, 5th.
5. 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:
Clean the TCM if necessary. Excessive road debris reduces the effectiveness of the heat sink on the TCM and could cause internal temperature to rise.