Eaton Fuller Hybrid Transmission Fault Code 51 – Rail Position Sensor
Fault code for Eaton Hybrid Drive Systems models (MY08) EH-8E306A-U, EH-8E306A-UPG, EH-8E306A-UP, EH-8E306A-CD, EH-8E306A-T, EH-6E606B-CD, (MY09) EH-8E406A-U/P, EH-8E406A-UP, EH-8E406A-UPG, EH-8E406A-CD, EH-8E406A-CDG, EH-8E406A-CDR, EH-8E406A-T, EH-6E706B-CD, EH-6E706B-P and EH-6E706B-UPG. Read below to learn how to test, clear and fix fault code errors for your Freightliner, Mack, Peterbilt, Kenworth, Volvo and International truck. The Rail Position Sensor is a Hall Effect position sensor that provides feedback on the position of the shift finger. The Transmission Electronic Control Unit (TECU) delivers a constant 5-volt reference to 1 terminal of the Rail Position Sensor. The signal output from sensor provides a regulated voltage signal from 0.5–4.5 volts. The last terminal provides a ground for the Rail Position Sensor to the TECU.
Fault Code 51 – Rail Position Sensor Detection
The following preconditions must be met before the system detects the fault:
- TECU ignition voltage is greater than 7 volts and less than 16 volts.
- FMIs 3 and 4 do not set if the TECU System Battery Voltage Low fault is Active. FMI 2 do not set if FMI 3, 4 is Active.
Note: When troubleshooting an Inactive code refer to the Product Diagnostic Mode (PDM)
Conditions to Set Fault Code Active
- FMI 2 sets when the transmission controller detects the Rail Sensor voltage is above 4.5 volts or below 0.5 volts for 1 second of longer.
- FMI 3 sets when the transmission controller detects the Rail Sensor supply voltage is 5% above the expected supply voltage for 1 second or longer.
- FMI 4 set when the transmission controller detects the Rail Sensor supply voltage is 5% below the expected supply voltage for 1 second or longer.
- FMI 10 (refer to troubleshooting guide TRTS0930)
Fallback When Fault Code 51 is set the following conditions occur:
- Red “Service” light illuminates and an “F” flashes in the gear display.
- Fault is stored in TECU memory.
- If this fault occurs while moving, the transmission remains in the current gear and the clutch opens when the vehicle stops.
- The operation mode changes to “AutoShift Fallback” mode.
Conditions to Set Fault Code Inactive
Only Inactive faults can be cleared from the Transmission Electronic Control Unit (TECU) or HCM history using ServiceRanger. The TECU automatically clears the faults from history after 200 hours and the HCM automatically clears the faults from history after the fault has been Inactive for 200 hours.
This fault code can be caused by any of the following:
- FMI 2, 10
- Transmission Harness
- Rail Position Sensor
- FMI 3, 4
Fault Code 51 – Rail Position Sensor Test
Harness Front View
(TECU – System Interface Connector)
Rail Position Sensor Pins
NOTE: Refer to the Eaton Hybrid Component and Connector Location for Connector Locations in MY08 Systems
NOTE: Refer to the Eaton Hybrid Component and Connector Location for Connector Locations in MY09 Systems.
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