Eaton Gen 2 (AutoShift) Fault Code: 56 PID: 161 FMI: 5 Input Shaft Speed Sensor

Posted by PerDiezel Solutions on May 12, 2026

Overview:
Fault Code 56 indicates an electrical problem in the Input Shaft Speed Sensor circuit. The signal from the sensor did not match the current operating conditions.

Detection:
A Speed Sensor is determined faulty when all the Speed Sensor readings are compared and at least one sensor is inconsistent.

Fallback:
This fault causes an in-place fallback. If the Input Shaft Speed Sensor fails before power up, the transmission is unable to engage a gear and the fault code cannot be reproduced.

Possible Causes:
1) Transmission Harness
2) Input Shaft Speed Sensor
3) Various Transmission Components
4) Transmission Controller

Shop Talk:
Select a forward gear and drive at a steady speed no slower than 10 MPH. It may be necessary to operate the vehicle for a prolonged period of time if the cause of the failure is related to heat and vibration.

Eaton Gen 2 (AutoShift) Fault Code: 56 PID: 161 FMI: 2 Input Shaft Speed Sensor

Eaton Gen 2 (AutoShift) Fault Code: 52 PID: 59 FMI: 4 Gear Select Sensor

Eaton Gen 2 (AutoShift) Fault Code: 52 PID: 59 FMI: 3 Gear Select Sensor

Eaton Gen 2 (AutoShift) Fault Code: 52 PID: 59 FMI: 2 Gear Select Sensor

Eaton Gen 2 (AutoShift) Fault Code: 51 PID: 60 FMI: 10 Rail Select Sensor

Eaton Gen 2 (AutoShift) Fault Code: 51 PID: 60 FMI: 4 Rail Select Sensor

WARNING!