Global SCR Fault Code
Free · no signupSPN 4364 FMI 18
Progressive power loss; "Emissions Failure" warning; Excessive DEF consumption.
System
Not specified
Symptom
Progressive power loss; "Emissions Failure" warning; Excessive DEF consumption.
Diagnosis & fix steps
SCR NOx Conversion Efficiency Low.
LOGIC: The Outlet NOx sensor is seeing too much NOx compared to the Inlet sensor, meaning the catalyst is not working.
ACTION: 1. Check DEF injector for a "crystal" (white rock) buildup.
2. Verify DEF pump pressure (usually 5–9 bar).
3. Check for exhaust leaks at the turbo or bellows.
FIX: Clean DEF Injector tip with hot water; replace DEF Pump or SCR Catalyst.
Red Seal field insights
Before replacing an expensive SCR brick, check for exhaust leaks. If oxygen leaks into the pipe before the sensor, it "tricks" the sensor into thinking the NOx is high, triggering a false efficiency code.
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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