Overview:
Fault Code 93 indicates the Transmission Controller is not receiving J1939 messages from the engine.

Detection:
The fault is detected if J1939 communication from the engine is lost for 5 seconds.

Fallback:
If the fault occurs while moving, it causes a 1-speed fallback. Once vehicle has stopped, the starting gear and reverse can be engaged. If the failure occurs at system initialization, it causes an AutoSelect fallback mode.

Possible Causes:
1) OEM supplied J1939 harness
2) Engine ECM

Shop Talk:
Key on. If the fault is present, the system should automatically detect the problem and set the code. If the fault is not present at key on, operate the vehicle and attempt to duplicate the driving conditions that triggered the fault code. Possible triggers include heat, vibration.