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Check Engine Light P0401 on 2018 Ram 2500 Cummins - EGR Flow Insufficient

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Melissa G. · rep 0 · May 22, 3:33 AM · 1 replies · solved · Question

My 2018 Ram 2500 with the 6.7L Cummins just threw a Check Engine Light. The code is P0401, which points to insufficient EGR flow. I've noticed a slight decrease in power and maybe a bit more smoke than usual.

The truck has about 85,000 miles on it. I do a lot of towing, and I'm wondering if this is a common issue with these trucks. I'm trying to avoid a costly dealership visit if it's something I can tackle myself or at least diagnose further.

Any advice on troubleshooting this? Could it be a clogged EGR cooler or valve, or something else entirely related to the DEF system?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:33 AM

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ClearTheCode guidance (Ram · Engine & drivetrain)

Summary: For Check Engine Light P0401 on 2018 Ram 2500 Cummins - EGR Flow Insufficient, work through these steps on your 2016+ vehicle:

  1. Confirm the symptom — note when it happens (cold start, highway, after fuel fill, etc.).
  2. Scan codes — save all pending/stored DTCs; don't clear until you've recorded them.
  3. Check TSBs & recalls — look up your VIN for open campaigns and known fixes.
  4. Inspect the obvious — related fuses, connectors, fluid level, and recent repairs.
  5. Test the common fix — follow model-specific service procedures; one change at a time.
  6. Escalate if needed — burning smell, no brakes, overheating, or stalling in traffic → shop visit.

Owner reported: My 2018 Ram 2500 with the 6.7L Cummins just threw a Check Engine Light. The code is P0401, which points to insufficient EGR flow. I've noticed a slight decrease in power and maybe a bit more smoke than usual.

The truck has about 85,000 miles on it. I do a lot of towing, and I'm wondering if this is a common issue with these trucks. I'm trying to avoid a costly dealership visit if it's something I…

This is educational guidance, not a substitute for hands-on diagnosis.

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