P0400 error code

2008 FORD FOCUS
89,000 MILES • 1.8L • 2WD • MANUAL
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BAYLIS_SARAH
  • MEMBER
  • 1 POST
The engine light keeps coming on and when I use a code reader it comes up p0400 exhaust gas re-circulation flow.
I have cleaned with erg spray and replaced the air box intake hose. The engine light will come on and then turn off itself a day later so I'm wondering could it be a sensor fault? Not sure what else to try before taking the car to a garage.
Jun 26, 2019 at 3:12 AM
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STEVE W.
  • ✓Experienced Mechanic
  • 15,381 POSTS
Welcome to 2CarPros. The usual culprit for this is carbon build up in the EGR passages themselves. Cleaning them involves taking the EGR off and using something like a flexible cable on a drill to knock the carbon build up in the passages free. Sprays don't do much in this case as they cannot get to the area of the build up. On extreme cases the manifolds may need to be removed to clear the passages out.
Jun 26, 2019 at 4:56 AM
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