In my opinion EGR codes are quickly climbing the ladder of the most common causes of check engine light failures to be found on aging automobiles. This is often due to carbon clogging passageways or improper operation of the egr-valve. Common failed components are available below for purchase.
Several technical service bulletins for a wide variety of different makes and models have documented a few different problems associated with the EGR valve system. With some EGR problems you might set a diagnostic trouble code of PO401 or P0402.
You may also set trouble codes for an engine misfire, which would be in the PO300 range. It is also possible that your check engine light will not come on and you will just experience a noticeable problem such as rough engine idle or even engine stalling.
Exhaust gas recirculation valveA basic explanation of the EGR valve would probably help with the understanding of the diagnosis and repair of EGR codes. Exhaust gas recirculation is necessary for emissions purposes.Unfortunately when it malfunctions it can actually push emission levels off the chart. The valve meters post combustion exhaust gases to be mixed with the intake fuel charge and this dilutes the mixture.
Allowing exhaust gas to flow into the combustion chamber reduces cylinder temperatures and therefore reduces the amount of nitrogen oxides produced at the tail pipes. Of course this system works hand in hand with other computer controlled on board emissions systems such as the catalytic converter and oxygen sensors to name a few.
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