Selective exhaust gas recirculation diagnostic systems and methods

1. A system for a vehicle, comprising:

a first exhaust gas flow rate (EGF) estimation module that estimates a first flow rate of exhaust re-circulated back to an intake manifold based on a concentration of oxygen in the intake manifold;

a second EGF estimation module that estimates a second flow rate of exhaust re-circulated back to the intake manifold using one of a function and a mapping that relates an engine speed, an engine load, and an opening of an exhaust gas recirculation (EGR) valve to the second flow rate;

an EGF fault detection module that selectively indicates that a fault is present in an EGR system based on the first flow rate and the second flow rate,

wherein, when the EGR valve is closed, the EGF fault detection module selectively indicates that a leak is present in the EGR valve based on a first difference between the first flow rate and a predetermined flow rate, and

wherein, when the EGR valve is open, the EGF fault detection module selectively indicates that the leak is present based on a second difference between the first flow rate and the second flow rate; and

a triggering module that disables the EGF fault detection when a change in the engine speed is greater than a predetermined speed and when a change in the engine load is greater than a predetermined load.

2. The system of claim 1 wherein the fault indicates at least one of a faulty intake oxygen (IO) sensor, a faulty exhaust oxygen (EO) sensor, a faulty engine speed sensor, the EGR valve opening differently than intended, and pulsating exhaust flow.

3. The system of claim 1 wherein

the first EGF estimation module estimates the first flow rate of exhaust re-circulated back to the intake manifold based on the concentration of oxygen in the intake manifold measured using an intake oxygen sensor and a concentration of oxygen in an exhaust system measured using an exhaust oxygen sensor.

4. The system of claim 1 wherein the EGF fault detection module indicates that the leak is present when the first difference is greater than a predetermined value.

5. The system of claim 1 wherein the EGF fault detection module indicates that the leak is present when the second difference is greater than a predetermined value.

6. A method comprising:

estimating a first flow rate of exhaust re-circulated back to an intake manifold based on a concentration of oxygen in the intake manifold;

estimating a second flow rate of exhaust re-circulated back to the intake manifold using one of a function and a mapping that relates an engine speed, an engine load, and an opening of an exhaust gas recirculation (EGR) valve to the second flow rate;

selectively indicating that a fault is present in an EGR system based on the first flow rate and the second flow rate;

when the EGR valve is closed, selectively indicating that a leak is present in the EGR valve based on a first difference between the first flow rate and a predetermined flow rate;

when the EGR valve is open, selectively indicating that the leak is present is based on a second difference between the first flow rate and the second flow rate; and

disabling the indication when a change in the engine speed is greater than a predetermined speed and when a change in the engine load is greater than a predetermined load.

7. The method of claim 6 wherein the fault indicates at least one of a faulty intake oxygen (IO) sensor, a faulty exhaust oxygen (EO) sensor, a faulty engine speed sensor, the EGR valve opening differently than intended, and pulsating exhaust flow.

8. The method of claim 6 wherein

estimating the first flow rate of exhaust re-circulated back to the intake manifold comprises estimating the first flow rate based on the concentration of oxygen in the intake manifold measured using an intake oxygen sensor and a concentration of oxygen in an exhaust system measured using an exhaust oxygen sensor.

9. The method of claim 6 further comprising indicating that the leak is present when the first difference is greater than a predetermined value.

10. The method of claim 6 further comprising indicating that the leak is present when the second difference is greater than a predetermined value.