The Quick Answer above is the generic definition. What follows is the model-specific detail for the Ford models that log P0400.
DTC/P0400·Ford
P0400 on Ford: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Ford
P0400 on a Ford means the engine control unit has detected that exhaust gas recirculation flow is not within the expected range. The EGR system recirculates a portion of exhaust gas back into the intake to lower combustion temperatures and reduce NOx emissions. A blockage or valve failure disrupts this flow.
Typical repair cost, all makes€50 - €1400
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Ford Focus
2005-2022The 1.6 TDCi uses the same DV6 diesel as Peugeot's 1.6 HDi. Depending on the version, its EGR valve is either vacuum-controlled through a solenoid or fully electric, so check which type is fitted before testing it. Both types clog with carbon, and a vacuum-controlled valve can also fail at the diaphragm.
What causes P0400 on a Ford?
Beyond the generic causes listed on the main P0400 page, these are the patterns noted for Ford models:
Ford FocusEGR valve diaphragm failure on vacuum-controlled 1.6 TDCi valves
Ford FocusCarbon clogging of the EGR valve and passages on the 1.6 TDCi
How to diagnose P0400 on a Ford with OBD2
Follow these steps to pinpoint the root cause of P0400:
- Check for companion EGR codes (P0401, P0402, P0403) that may help narrow down whether the issue is insufficient flow, excessive flow, or an electrical fault
- Remove the EGR valve and visually inspect for carbon buildup. A heavily clogged valve is the most common cause and can be cleaned with carburettor cleaner
- With the EGR valve removed, inspect the intake and exhaust passages for carbon blockage. Use a flashlight and probe to check passage diameter
- Test the EGR valve: apply vacuum to a vacuum-operated valve, or on an electronic valve command it open and closed with manufacturer-level software (a generic OBD2 reader cannot run this actuator test). It should open and close smoothly
- If the valve operates correctly, compare commanded and actual EGR in live data (standard OBD2 values on many cars) and check the DPFE or EGR position sensor against the manufacturer specification
How much does P0400 cost to fix on a Ford? (EUR)
Estimated repair costs for P0400 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 P0400
These codes are often seen alongside P0400 or point to related issues, on any make:
Looking for the full P0400 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0400 guideSkanyx · Ford
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