If you own a car that was built after 1996, it has a great feature called an OBD sensor. This sensor allows you to diagnose any issues that your car may have by plugging a small reader in and retrieving computer codes. If you've received a code of P0401, it means that you have insufficient EGR flow. To understand why this is an issue, you first should know what an EGR is.

What Does EGR Mean?

EGR stands for Exhaust Gas Recirculation. This system lowers your car's emissions by recirculating a portion of the exhaust back into the engine. This helps reduce the amount of hydrocarbons that are emitted by burning any traces left in the exhaust. If the EGR has gone bad, the valve is no longer returning that exhaust, which also means that it is unlikely that your car will pass the required annual emissions inspection.

It's likely that you've already experienced some of the symptoms of EGR failure and not realized it. Some of the symptoms include a light pinging when accelerating or traveling at high speeds. Other times, the only indication of a problem is the check engine light activating.

What Are the Causes and How Do You Fix Them?

There are four main reasons for an EGR fault. The first is a bad EGR valve. The valve can tear or wear out with use. Repairing the valve is a simple matter, but it's also recommended that your mechanic check the pintle for any major carbon deposits. Another reason for a P0401 code is a blockage in the EGR tubing due to carbon buildup. In this case, replacing the lines is a simple fix. Again, the valve and pintle should also be checked. In a rare case, the EGR sensor has simply gone bad. Replacing this sensor is a fairly easy procedure, but the rest of the EGR system should also be inspected.

There are less common causes for EGR failure including a fault with the car's computer. If inspection and replacement of the EGR sensor and valve do not clear the code, there are other systems that can cause cascade faults. These include the Manifold Absolute Pressure (MAP) sensor, the EGR temperature sensor, the EGR Valve Position (EVP) sensor, and the Differential EGR Pressure Feedback (DPFE) sensor.

While P0401 doesn't indicate an exceptionally difficult issue to fix, it is one that is important to take care of. Left unattended, an EGR failure can also cause faults in the exhaust system; make sure to have the code checked and cleared by a licensed mechanic like Arringdale's Engine Rebuilding & Auto Repair.