Universal HD Fault Code

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SPN 3556 FMI 05

Regen Aborted / DPF Overload Light

System

Aftertreatment / DPF

Symptom

Regen Aborted / DPF Overload Light

Diagnosis & fix steps

LOGIC: Hydrocarbon (7th Injector / Doser) Fuel Injector Circuit Open. ACTION: Measure coil resistance on the exhaust fuel dosing injector solenoid (spec: ~10–15Ω). Inspect 2-pin harness connector for broken terminal locking tabs or oil/water wicking; trace wiring back to aftertreatment control module.

Red Seal field insights

Active Regen Interruption: Active regeneration relies on the 7th injector (doser) to mist raw diesel fuel into the exhaust stream ahead of the DOC to generate catalytic burn heat. An open circuit disables all active regeneration cycles.

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.

Book an uptime review

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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