Method for diagnosing a low pressure exhaust gas recirculation system of an internal combustion engine and device for carrying out the method

A device for diagnosing a low pressure exhaust gas recirculation system of an internal combustion engine, comprising:

• a control device having at least one unit for determining an estimated value for a low pressure exhaust gas recirculation mass flow, and a subtractor for determining a difference;
• wherein the control device is configured for:
• measuring, the internal combustion engine having an intake area for supplying fresh air which includes in succession in the flow direction a first section having a low pressure in which an air mass flow sensor is situated, a compressor and a second section having a high pressure, the exhaust area of the internal combustion engine including a first section having a low exhaust gas pressure, and the low pressure exhaust gas recirculation system which has an adjustable low pressure exhaust gas recirculation valve recirculating at least a portion of the exhaust gas in the second section of the exhaust area to the first section of the intake area, by the air mass flow sensor the fresh air mass flow taken in;
• ascertaining the total mass flow flowing through the compressor;
• ascertaining the low pressure exhaust gas recirculation mass flow from the difference between the total mass flow and the fresh air mass flow;
• determining an estimated value for the low pressure exhaust gas recirculation mass flow;
• forming a difference, by the subtractor, between the ascertained low pressure exhaust gas recirculation mass flow and the estimated value;
• and
• outputting an error signal in the event of a deviation.

A computer readable medium having a computer program, which is executable by a processor, comprising:

• a program code arrangement having program code for diagnosing a low pressure exhaust gas recirculation system of an internal combustion engine, by performing the following:
• measuring, the internal combustion engine having an intake area for supplying fresh air which includes in succession in the flow direction a first section having a low pressure in which an air mass flow sensor is situated, a compressor and a second section having a high pressure, the exhaust area of the internal combustion engine including a first section having a low exhaust gas pressure, and the low pressure exhaust gas recirculation system which has an adjustable low pressure exhaust gas recirculation valve recirculating at least a portion of the exhaust gas in the second section of the exhaust area to the first section of the intake area, by the air mass flow sensor the fresh air mass flow taken in;
• ascertaining the total mass flow flowing through the compressor;
• ascertaining the low pressure exhaust gas recirculation mass flow from the difference between the total mass flow and the fresh air mass flow;
• determining an estimated value for the low pressure exhaust gas recirculation mass flow;
• forming a difference between the ascertained low pressure exhaust gas recirculation mass flow and the estimated value;
• and
• outputting an error signal in the event of a deviation.