What does P0401 mean on a Nissan?

On Nissan vehicles, the P0401 code indicates: EGR monitor detected exhaust gas flow is below expected rate during commanded EGR on test.

Is it safe to drive my Nissan with a P0401?

You can drive for a short distance, but you should inspect your Nissan as soon as possible to avoid further damage.

P0401

Nissan Exhaust Gas Recirculation Flow Insufficient Detected

Specialized diagnostic report for Nissan owners dealing with the P0401 fault code.

Technician's Overview

🟡 SERVICE SOON

EGR monitor detected exhaust gas flow is below expected rate during commanded EGR on test. When this code is triggered in a Nissan, the engine control module (ECM) has detected an issue with the EGR System system.

Common Symptoms

Engine ping / knock at light throttle on acceleration in my Nissan
Rough cold start in some configurations in my Nissan
MIL on in my Nissan

Probable Causes

Clogged EGR passages — carbon buildup blocking flow port in intake manifold
Faulty EGR valve (stuck closed or diaphragm failure on vacuum-operated type)
DPFE sensor failure (Ford-specific — differential pressure sensor)
Clogged EGR cooler (diesel engines)

Recommended Fixes for Nissan

Remove EGR valve; inspect and clean passages with EGR cleaner and a wire brush
Test EGR valve operation: vacuum-type — apply 15 inHg, idle should drop; electronic — command with scan tool
Ford DPFE sensor: inspect hoses for cracks, test sensor output voltage (0.5 V key-on, rises with EGR flow)
Replace EGR valve if stuck or diaphragm is perforated ($25–120 DIY)

QUICK FIX TOOL

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