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Diagnosing, Fixing EGR Issues

EGR valve

Most modern vehicles are equipped with exhaust gas recirculation (EGR) to re-burn some of the exhaust gases to improve emissions. This system is relatively simple in its operation. There are three things most likely to go wrong if your engine's computer is throwing an EGR code.

The first is sensors. These are what would determine that there is a problem in the first place and are often what goes wrong as well. They are the most sensitive portion of the EGR system. Most EGR valves are actuated by the computer based on information gained from oxygen and air intake sensors. These sensors can go bad or send false readings. Problems in them, their circuits, or the computer itself can mean a triggering of an EGR code.

Testing sensors is not easy, but the most reliable way to do it is to replace the sensor with one known to be working properly and see if things change. There are also specialized tools that can mimic sensor readings or override the sensor's input to the ECU and give false readings to see if things change.

The second most common issue will be the valve itself. EGR valves can stick or become only partially operable, limiting how well they can open or close. A stuck EGR valve is relatively easy to diagnose given that it will often either choke the engine off at idle (if stuck open) or cause the engine to run too clean and get poor fuel economy (if stuck closed).

The ECU expects the EGR to be open or closed as it demands and if the EGR doesn't comply, there isn't much that the computer can do to compensate. In this case, cleaning or replacement of the EGR is the fix. The EGR valve on most common passenger vehicles costs less than $100 and can be easily replaced by most DIY mechanics. Similarly, cleaning can be attempted by most as well and should be tried if at all possible.

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