The Quick Answer above is the generic definition. What follows is the model-specific detail for the Ford models that log P0401.
DTC/P0401·Ford
P0401 on Ford: Causes, Symptoms and Fix Cost
Quick Answer
Low SeveritySafe to drive (short-term)Ford
P0401 on a Ford means the engine computer detected too little exhaust gas flowing back through the EGR (Exhaust Gas Recirculation) valve into the intake. That recirculated exhaust dilutes the intake charge to lower nitrogen oxide emissions and combustion temperature. By far the most common cause is carbon buildup clogging the EGR valve or passages, especially on diesels and direct-injection petrol engines. A clean usually costs 80 to 200 EUR.
Typical repair cost, all makes€8 - €550
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Ford Focus
2005-2024Where a Ford petrol engine uses a DPFE (Delta Pressure Feedback EGR) sensor, a cracked or blocked DPFE hose is a frequent P0401 trigger that mimics a clogged valve, so test the DPFE sensor and its two rubber hoses before condemning the valve. The 1.6 and 2.0 TDCi diesels follow the usual soot-clogging pattern.
What causes P0401 on a Ford?
Beyond the generic causes listed on the main P0401 page, these are the patterns noted for Ford models:
Ford FocusCracked or blocked DPFE sensor hoses giving a false low-flow reading on petrol engines
Ford FocusFaulty DPFE sensor itself misreporting EGR flow
Ford FocusSoot-clogged EGR valve and passages on 1.6/2.0 TDCi diesels
How to diagnose P0401 on a Ford with OBD2
Follow these steps to pinpoint the root cause of P0401:
- Read freeze-frame data and confirm P0401 (flow insufficient) rather than P0402 (flow excessive) or an electrical valve code, since the fix differs
- Remove the EGR valve and inspect for heavy carbon deposits on the pintle and seat, a caked valve that will not seat or open cleanly is the most common finding
- Command the valve open with manufacturer-level software (electronic valves; a generic OBD2 reader cannot run this test) or apply vacuum (vacuum-operated), a working valve makes the engine stumble or stall as exhaust floods the intake
- If the valve opens correctly, probe the EGR passages and intake manifold galleries for carbon blockage that restricts flow downstream of the valve
- On DPFE-equipped vehicles (many Fords), test the DPFE sensor and its two rubber hoses for cracks, blockage, or swapped connections that skew the flow reading
- On diesel engines, inspect the EGR cooler for soot blockage or internal coolant leaks, and check vacuum supply hoses on any vacuum-operated system for cracks or disconnection
- Clear the code, drive a full warm-up cycle, and rescan to confirm flow now meets the commanded target before condemning a part
How much does P0401 cost to fix on a Ford? (EUR)
Estimated repair costs for P0401 in EUR, compiled across makes. Ford costs typically sit in the middle of each range.
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
Codes related to P0401
These codes are often seen alongside P0401 or point to related issues, on any make:
Looking for the full P0401 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0401 guideSkanyx · Ford
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