P0401
Medium SeverityEGR Insufficient Flow
Emissions System
P0401 — Instant Answer
EGR Insufficient Flow
Severity: MEDIUM SEVERITY
Meaning: The EGR is not flowing enough exhaust gas. Usually carbon buildup blocking the passages.
Safe to drive? Usually yes with caution, but confirm root cause before long trips.
Estimated repair cost: $20 - $150
Most common causes:
- 1. Carbon buildup in EGR passages (35-45% of cases)
- 2. Stuck-closed EGR valve (10-25% of cases)
- 3. Failed EGR position sensor (10-25% of cases)
Symptoms
- ⚠️Ping/knock under load
- ⚠️Failed emissions test
- ⚠️Check engine light
Related Symptoms
Common Causes
How to Diagnose P0401
- 1Clean EGR valve and intake passages
- 2Test EGR valve with vacuum pump
- 3Check DPFE/EGR pressure sensor
OEM Procedures for P0401
Exhaust Gas Recirculation Flow Insufficient Found 8 OEM service manual procedures.
Adjustment/Replacement - Specification
Adjustment/Replacement - Specification
Adjustment/Replacement - Specification
Adjustment/Replacement - Specification
Adjustment/Replacement - Specification
Adjustment/Replacement - Specification
Adjustment/Replacement - Specification
Adjustment/Replacement - Specification
OEM Diagnostic Flowchart
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Related Resources
Repair guides, symptom pages, and wiring diagrams related to P0401.
OEM Manual Evidence
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Related Symptoms
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Open the exact vehicle hub for a repair workflow commonly associated with P0401.
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Open the exact repair flow most commonly associated with P0401 on this vehicle.
Open the exact repair flow most commonly associated with P0401 on this vehicle.
Open the exact repair flow most commonly associated with P0401 on this vehicle.
Open the exact repair flow most commonly associated with P0401 on this vehicle.
Related Codes
Frequently Asked Questions
- Can I clean the EGR valve myself?
- Yes — remove it and clean with carb cleaner and a brush. Also clean the intake port/passage.
- Is P0401 common on certain cars?
- Very common on Fords with the DPFE sensor. Replacing the DPFE sensor often fixes it for $30-$50.
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Author & Review
Written by AllOEMManuals Editorial Team. Reviewed by ASE-certified technicians and updated with factory-reference checks for fitment-sensitive steps.
This guide was drafted with AI assistance and reviewed for accuracy by a human editor.
Last updated: 2026-05-07