What does LGMG fault code SPN 157 FMI 00 mean?

Q: What does LGMG fault code SPN 157 FMI 00 mean?

SPN 157 FMI 00 indicates: Hard Engine Knock / Black Smoke / Limp Fix: LOGIC: Rail Pressure Exceeds Upper Safe Limit (Overpressure Spike). ACTION: Inspect the Fuel Metering Unit (MeUn / PCV) on the high-pressure pump. Test coil resistance (spec: ~2.8–3.5Ω); remove the valve and check the sliding internal spool for fine particle sticking or lacquer build-up from dirty fuel.

LGMG Fault Code

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SPN 157 FMI 00

Hard Engine Knock / Black Smoke / Limp

System

Fuel / High Pressure

Symptom

Hard Engine Knock / Black Smoke / Limp

Diagnosis & fix steps

LOGIC: Rail Pressure Exceeds Upper Safe Limit (Overpressure Spike). ACTION: Inspect the Fuel Metering Unit (MeUn / PCV) on the high-pressure pump. Test coil resistance (spec: ~2.8–3.5Ω); remove the valve and check the sliding internal spool for fine particle sticking or lacquer build-up from dirty fuel.

Red Seal field insights

Stuck Metering Spool: Fine silt and contaminated bulk fuel wedge the pump suction control valve in the open flow position, sending full displacement to the rail and blowing open the mechanical rail relief valve.

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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