Eaton Gen 1 (AutoShift) Fault Code: 41 PID: SID 56 FMI: 7 Range Failed To Engage

Posted by PerDiezel Solutions on May 12, 2026

Overview:
This code indicates the transmission is unable to complete a shift across the range. The range is either stuck in HI or LO, or cannot complete engagement in HI or LO.

Detection:
The transmission attempts the same range shift five consecutive times and determines the shift cannot be completed based on the speeds across the back box.

Fallback:
This fault causes a 5-speed fallback and the transmission stays in either LO range or HI range. When the vehicle comes to a stop, an attempt to shift into LO range is made.

Required Tools:
1) Basic Hand Tools
2) (2) 0-100 PSI Air Pressure Gauges
3) AutoSelect/AutoShift Troubleshooting Guide

Possible Causes:
1) Low air pressure
2) Contaminated air supply
3) Air leak
4) Range solenoid stuck
5) Failed range synchronizer
6) Failed range actuator/cylinder/piston/yoke

Eaton Gen 1 (AutoShift) Fault Code: 35 PID: SID 231 FMI: 7 Engine Control Failure

Eaton Gen 1 (AutoShift) Fault Code: 35 PID: SID 231 FMI: 2 Engine Control Failure

Eaton Gen 1 (AutoShift) Fault Code: 33 PID: PID 168 FMI: 4 Battery Voltage Supply

Eaton Gen 1 (AutoShift) Fault Code: 31 PID: PID 62 FMI: 4 Engine Brake Relay Coil

Eaton Gen 1 (AutoShift) Fault Code: 31 PID: PID 62 FMI: 3 Engine Brake Relay Coil

Eaton Gen 1 (AutoShift) Fault Code: 17 PID: SID 237 FMI: 4 Start Enable Relay Coil

WARNING!