Eaton UltraShift PLUS Fault Code
Free · no signupFault Code 35 / SPN 520235
Flashing "F" on Gear Display / No Crank
System
Power Supply
Symptom
Flashing "F" on Gear Display / No Crank
Diagnosis & fix steps
LOGIC: Low Battery Voltage During Shift Actuator Motor Engagement.
ACTION: Perform a carbon-pile load test on truck battery bank. Clean the heavy 30A inline power harness and ground ring terminals bolted directly to the starter ground stud.
Red Seal field insights
High Amperage Surge: Electric shift rail motors pull up to 40 amps during gear shifts; high-resistance terminal connections drop line voltage, causing the TCM to freeze shift sequences mid-throw.
Same code keeps coming back?
That's a program problem, not a part problem. Book a 30-minute uptime review with Grant, a Red Seal Heavy Duty Technician.
Read before you touch anything
- This is general reference information, not a repair manual. It is for trained, qualified technicians.
- Fault codes, meanings and procedures vary by model, serial number and software version. Confirm the code and the procedure against the manufacturer's service manual before acting.
- Follow the OEM service manual, torque specs and your site's safety procedures: lockout/tagout, block raised equipment, relieve hydraulic, fuel and air pressure, and let hot systems cool.
- You use this information at your own risk. Adventure Mechanical and AM Fleet Integrity accept no liability for damage, injury, downtime or loss arising from its use.
- Not affiliated with or endorsed by any manufacturer. Brand names are used only to identify the equipment a code applies to.
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