P0401 – EGR Flow Insufficient

Description

The EGR system is not flowing enough exhaust gas.

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Symptoms

Rough idle
Hesitation
Poor acceleration
High NOx emissions
Check engine light

Causes

Clogged EGR passages
Faulty EGR valve
Vacuum leak
Faulty DPFE sensor
Carbon buildup

Diagnosis

Inspect EGR valve
Check vacuum lines
Test DPFE sensor
Inspect passages
Scan live data

Repair

Clean EGR passages
Replace EGR valve
Fix vacuum leaks
Replace DPFE sensor
Remove carbon buildup