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Autopart Mechanic

Autopa ... 4/12/2018

2012 BMW X1 xDrive28i 6 Cyl 3.00L


What does P0400 OBD-II Trouble Code and what are its causes? How do I fix the Exhaust Gas Recirculation Flow of my car?

1 Answer

PartsAvatar Ca

PartsAvatar Ca 4/12/2018

What the P0400 code means?

P0400 is an OBD-II generic code that the engine control module (ECM) detected the engine exhaust gas
recirculation (EGR) valve is not flowing recalculated exhaust gases when it is commanded to open the flow
of gases into the intake manifold.

What causes the P0400 code?

Plugged EGR passage which restricts the flow of exhaust gasses

Faulty EGR solenoid

Faulty EGR solenoid wiring/harness

Vacuum lines damaged/disconnected to the EGR valve solenoid or to the EGR valve

Faulty EGR valve

What are the symptoms of the P0400 code?

Check Engine Light will illuminate

In most cases, there are no adverse conditions noticed by the driver

In some cases, there may be performance problems, such as pinging on acceleration, when the engine is
under load or when driving the vehicle at higher speeds

Common mistakes when diagnosing the P0400 code

Replacing the EGR valve before checking for carbon build up on the EGR temperature sensor

Replacing the EGR valve without checking the EGR pressure transducer for proper function

What repairs can fix the P0400 code?

Replacing the EGR valve

Replacing a broken vacuum line to the EGR valve

Replacing an EGR temperature sensor or cleaning the carbon off of it to repair it

Cleaning carbon out of EGR tubes to intake manifold


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