I have a P0657 code after my Allison TCM was rebuilt.

The TCM controls the current supplied to the solenoids. If you're getting the P0657 code on a T14 A50 Allison TCM, please check the wiring for any bends, chaffing, or poor grounding.

Please check the harness and pins to ensure there is a good solid clean connection. You can use an automotive electronic plug spray that cleans connectors from any auto parts store. 

 

The secondary cause for this code is defective solenoids. Perform an active test with an OBDII scan tool will help determine if a solenoid is faulty.

 

The last and least likely cause for this code is a faulty TCM. If you've already checked the first two steps then please contact us so we can assist you further.