Eaton Fuller Advantage (2017) Fault Code: 57 PID: 160 SPN: FMI: 2 Main Shaft Speed Sensor: Data Erratic

Overview:
The Fuller Advantage transmission is equipped with four electronic speed sensors. The Input Shaft, Main Shaft and Output Shaft Speed Sensors are used to calculate gear ratios within the transmission. The Input Shaft Speed Sensor measures the rotational speed of the Input Shaft, taken from the upper countershaft drive gear. The Main Shaft Speed Sensor measures the rotational speed of the transmission gearing exiting the main case, taken from the auxiliary upper countershaft gear. The Output Shaft Speed Sensor measures the rotational speed of the output shaft taken from the Output Shaft Tone Wheel. The Transmission Electronic Control Unit (TECU) compares these speeds to calculate the gear ratios of the main case, auxiliary case and overall transmission.

The Main Shaft Speed Sensor transmits a voltage signal to the TECU based on the rotational speed of the gearing exiting the transmission main case. The TECU compares Main Shaft Speed to Input Shaft Speed to confirm the gear ratio of the main case and compares Main Shaft Speed to Output Shaft Speed to confirm the gear ratio of the auxiliary case.

Fault Code 57 indicates an electrical fault within the Main Shaft Speed Sensor circuit or a speed value that is inconsistent with the calculated gear ratios.

Detection:
The TECU compares the values of these three speed sensors to determine sensor validity. The TECU also monitors the Main Shaft Speed Sensor electrical circuit for any shorts to power, ground or open circuits.

Conditions to Set Fault Code Active:
The system can detect Main Shaft Speed Sensor faults when one of the following conditions is present for 1 second or longer:
FMI 2 – Data Erratic: TECU detects data being reported from the Input Shaft Speed Sensor does not match the current gear ratio in comparison with other sensors

Fallback:
All FMIs
• “F” flashes in gear display.
• Service light flashes (if equipped).
• If fault occurs in low range, transmission will not complete a high range shift.
• If fault occurs in high range, transmission will down shift into low range, but will not shift back into high range.

Conditions to Set Fault Code Inactive:
All FMIs: TECU receives a valid signal from the Main Shaft Speed Sensor and detects no electrical open or short circuits for 2 seconds.

Possible Causes:
All FMIs
1) Transmission Harness
– Bent, spread, loose or corroded terminals
– Wiring shorted to ground, shorted to power or open
2) Main Shaft Speed Sensor
– Internal failure
– Physical damage
3) Mechanical Transmission
– Auxiliary Drive Gear damage or failure
– Auxiliary Countershaft gear damage or failure