JMC Fault Code
Free · no signupP0401
Check Engine Light / Hesitation on Decel
System
Emissions / EGR
Symptom
Check Engine Light / Hesitation on Decel
Diagnosis & fix steps
LOGIC: Exhaust Gas Recirculation Flow Insufficient Detected.
ACTION: Remove EGR gas pipe connecting cooler to intake. Clean soot caking from the intake throttle mixer port. Verify vacuum switching valve holds vacuum under actuation.
Red Seal field insights
Intake Port Choke: Soot combines with PCV blow-by oil mist at the throttle mixing point, restricting the actual EGR delivery port to a pinhole.
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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