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P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient

What it means

The EGR system, which feeds a little exhaust back into the engine to lower emissions, isn't flowing enough.

Severity: Low to Moderate

Can I drive it? Usually drivable; you may notice pinging/knock under load. Fix to pass emissions.

Common causes (most likely first)

Carbon-clogged EGR passages
Faulty EGR valve
Faulty DPFE/EGR pressure sensor (Ford)
Vacuum hose or solenoid issue

Likely fixes

Clean EGR valve and passages
Replace EGR valve
Replace DPFE sensor/hoses (Ford)

DIY parts cost

$20–$300

Approximate estimate

Shop repair cost

$150–$700

Approximate estimate, parts + labor

DIY difficulty

Moderate

Varies by vehicle

Cost ranges are rough, approximate U.S. estimates and vary widely by vehicle, region, and parts brand. Always confirm the diagnosis before buying parts.

Parts you may need

EGR valveCheck price
DPFE sensorCheck price
EGR gasketCheck price
Throttle body/carb cleanerCheck price

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