Liebherr Fault Code

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P20EE-00

Derate Looming. The machine "sees" the exhaust is still dirty after the catalyst.

Variant 1

System

SCR Catalyst

Symptom

Derate Looming. The machine "sees" the exhaust is still dirty after the catalyst.

Diagnosis & fix steps

SCR NOx Catalyst Efficiency Below Threshold. LOGIC: The difference between the Inlet NOx and Outlet NOx sensors is too small. ACTION: Perform a DEF Quantity Test (Bucket Test) to ensure the pump is actually spraying.

Red Seal field insights

Pro-Tip: In the Middle East or high-dust regions, the DEF Filter inside the pump gets partially clogged. It sprays enough to not throw a pressure code, but not enough to clean the NOx, triggering P20EE. Red Seal Fix: Always change the pump filter first.

Variant 2

System

Aftertreatment (SCR)

Symptom

Efficiency Alert. "SCR Catalyst Efficiency Below Threshold."

Diagnosis & fix steps

Nitrogen Oxide (NOx) Conversion Too Low. LOGIC: The downstream NOx sensor sees too much NOx compared to the upstream sensor after DEF injection.

Red Seal field insights

Pro-Tip: This is often a "Crystal" code. Remove the DEF injector and check for a "white mountain" of dried urea at the inlet. If it's clogged, the DEF can't mist properly.

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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