Caterpillar Fault Code
Free · no signup3427-5
Active Regen Disabled / E1025 Derate.
System
Aftertreatment (DEF)
Symptom
Active Regen Disabled / E1025 Derate.
Diagnosis & fix steps
LOGIC: Aftertreatment Fuel Pump Relay Control: Current Below Normal.
ACTION: Check the 10A ARD fuel pump fuse. If intact, check for 24V supply at the relay socket and verify resistance across the relay control coil (pins 85/86).
Red Seal field insights
System Logic: The ECM sends a ground command to close this relay and trigger the ARD combustion pump. An FMI 5 means the ECM detects an open circuit/broken wire in that command loop.
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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