The Code Reader takes common DTCs, breaks down when and why they occur and looks at symptoms and causes to help listeners make an accurate diagnosis.

Our scan tool is reading a diagnostic trouble code of P0401– EGR Insufficient Flow.

P0401 sets when the control unit determines the EGR flow is less than expected based on the readings from different monitoring criteria.

EGR or exhaust gas recirculation is an emission control. At high combustion temperatures, oxides of nitrogen are formed. The EGR system directs exhaust gas into the intake to mix it with fresh air. This change in the composition of the intake air reduces the combustion temperatures, ultimately reducing the production of this harmful pollutant that forms smog and acid rain. Multiple different methods are used to monitor EGR operation depending on manufacturer, including EGR temperature, intake manifold pressure, front O2 sensor signal, EGR position sensor reading, spark knock and exhaust back pressure.

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