Several things can cause this code:
* EGR valve stuck closed or partially closed: This is the most common cause. The valve isn't opening properly to allow exhaust gas to flow.
* EGR valve clogged: Carbon buildup can prevent the valve from opening fully.
* Vacuum leak in the EGR system: A leak in the vacuum lines that control the EGR valve will prevent it from functioning correctly.
* EGR pressure sensor malfunction: The sensor that measures the EGR flow is faulty.
* Clogged EGR passages: The passages in the intake manifold or exhaust system that carry EGR gas can become blocked.
* Problems with the DPFE (Differential Pressure Feedback Exhaust) sensor: (Older models may use this sensor instead of an EGR pressure sensor)
* Faulty PCM (Powertrain Control Module): Although less common, a problem with the engine's computer itself can cause this code.
To diagnose the problem, a mechanic will need to inspect the EGR valve, vacuum lines, and related components. They may use a scan tool to monitor live data from the EGR system and to check for other related diagnostic trouble codes. Simply clearing the code won't fix the underlying problem; it will only temporarily remove the warning light.
