P0400 - OBD Trouble Code

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The error code P0400 can be defined as Exhaust Gas Recirculation Flow Malfunction.

The trouble code P0400 would start appearing when the engine control module would detect that the exhaust gas recirculation valve is not flowing recirculated exhaust gases when it has been a given a command to open the flow of gases into the intake manifold.

It is always good to gather more information. The components of the Exhaust Gas Recirculation system are EGR Valve, Engine Control Μodule Controlled Vacuum Switch Valve or EGR Solenoid and an EGR Vacuum Μodulator. It is the ECM which would control the EGR Solenoid depending on the engine and driving conditions. The opening and closing of the EGR valve is regulated by the EGR Vacuum Μodulator.

What causes this problem with the Exhaust Gas Recirculation Flow Malfunction?

• Vacuum lines might be damaged/disconnected to the EGR valve solenoid
• Some flaws in the EGR valve
• The EGR temperature sensor might not be registering a temperature change when the EGR valve is opened
• There might be clogged EGR passage which can restrict the overall flow of exhaust gasses
• Defects in the EGR solenoid
• The EGR solenoid wiring/harness might be quirky
• The EGR valve is not opening due to no vacuum opening the valve from the EGR control solenoid or the EGR not holding vacuum
• There can be blocked EGR passages

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2. EGR Valve Gasket - A broken EGR Valve Gasket can cause a lot of issues. It would be nice if you get it replaced on time.
3. Mass Air Flow Sensor - Everything is fine with the Catalytic Converter and still OBD code P0400 flashing? Then there is definitely some fault with the Mass Air Flow Sensor. Get it checked and replace if needed.
4. MAP Sensor - MAP Sensor is an important car part which should never be neglected. May be there is some fault in it due to which P0400 code may start flashing.
5. Oil Pressure Sender - A faulty Oil Pressure Sender can be troublesome. You can always rely on us as we have best auto parts for our customers.
6. Crankshaft Position Sensor - If everything is alright with Oil Pressure Sender, then there is surely some defect in Crankshaft Position Sensor. Get it replaced before the situation gets worse.
7. Engine Coolant Temperature Sensor - P0400 code can display due to some faults in the Engine Coolant Temperature Sensor. So, it is very important to replace the Engine Coolant Temperature Sensor with us at equitable prices.

Our main motive is to achieve customer satisfaction as for us our customers are everything and that’s why we will help you to diagnose P0400 code by mentioning some major symptoms below:

Common Symptoms

• The engine might have an engine ignition ping or knock on acceleration
• The engine might fail emissions from excessive NOx in the exhaust tests
• The check engine light can start illuminating and the code might be set in ECM memory

If you wish to correct this fault code, then you have to follow certain steps. Correcting a problem needs your careful attention. Here are some ways with the help of which you will be able to correct the OBD Code P0400:

• Replace the defective EGR valve
• The broken vacuum line to the EGR valve should be carefully replaced
• It is very important to replace the EGR temperature sensor or clean the carbon off of it to repair it
• Make sure to clean the carbon out of EGR tubes to intake manifold

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Here are some steps which you should follow in order to diagnose this fault code:

• The first step would be to carefully scan the codes and document the freeze frame data in order to verify the problem
• All the engine and ETC codes should be cleared and road test the car to verify whether the code comes back
• Visually check the vacuum hoses, wiring, and connections to the EGR valve and control solenoid along with the EGR temperature sensor
• Then disconnect and check the EGR valve is getting vacuum to the valve when the control solenoid opens on light to medium acceleration
• The EGR temperature sensor change should be checked and engine to bog down when the EGR is opened
• Remove EGR valve and temperature sensor to check for excessive carbon build-up or blockage of EGR tubes

Common Mistakes When Diagnosing The P0400 Code

• Most of the people simply replace the EGR valve before inspecting for carbon build up on the EGR temperature sensor
• It would be a bad decision to replace the EGR valve without checking the EGR pressure transducer for proper function