LGMG Fault Code

Free · no signup

SPN 520220 FMI 04

Brake Warning Buzzer / Long Stopping Distance

System

Braking / Charge

Symptom

Brake Warning Buzzer / Long Stopping Distance

Diagnosis & fix steps

LOGIC: Dual-Circuit Brake Air Pressure Sensor Circuit Low. ACTION: Inspect brake air tank pressure switch on front frame. Test continuity when air builds past 0.55 MPa; check mechanical air compressor unloader valve and drain moisture from primary pneumatic reservoir.

Red Seal field insights

Waterlogged Wet Tanks: High-humidity operations without daily air tank draining flood the pneumatic booster chambers with oily water, corroding the pressure switch contacts and destroying booster seals.

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.

Track this across your whole fleet

This code is free to read. AM Fleet Integrity lets your team log fault codes against assets, plus the full fault-code library, QR operator reporting, PM scheduling and predictive alerts. Start free — no credit card required.

Start your free trial

Related LGMG fault codes

← All LGMG fault codes