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Q: Diagnostic code p0401

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I have changed the dpfe sensor the egr solenoid and the egr valve itself yet the check engine light continues to come back on with the same code.

My car has 315000 miles.

A: An often missed part of the EGR system is t...

An often missed part of the EGR system is the passages in the exhaust manifold and intake manifold and the tube that connect the EGR valve to the exhaust manifold can become clogged with carbon. If there are any exhaust leaks, this can cause problems as well, but the most common issue after the DPFE and the EGR valve are clogged ports. Your ford will have rubber hoses that can become clogged as well. They are usually replaced with the DPFE.

A simple test for clogged EGR passages, is to remove the EGR valve and start the car. If there isn’t an exhaust leak, it is clogged. Remember to check the ports in the intake manifold as well. With the EGR valve removed, there will be a massive vacuum leak. If not, the passages in the intake are clogged. The hot gases meet the cooler intake manifold and condense, leaving carbon build up. Your configuration may differ from my description here, but what’s important is to check all the passages of the EGR system.

Cleaning clogged EGR ports can often be difficult and time consuming to clean. Often times removing the exhaust manifold and or the intake manifold is necessary. Once you have gained access to all the ports, you will need to dig the carbon out with a screw driver or large pick. This will take care of the majority of the carbon, but you should use carburetor cleaner to remove the rest. Often you will need to use a combination of carb cleaner and digging with a pick to thoroughly clean the EGR passage. It is in your best interest to remove as much as possible.

I’d suggest getting some assistance from a qualified technician, such as one from YourMechanic, if you need help with getting this done. A mechanic will be able to further diagnose your Check Engine Light and help you fix it accordingly.

Good luck! I hope this helps you out.

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