Diagnostic for two-mode variable valve activation device

1. A method for diagnosing a multi-mode valve train device for selectively providing high lift and low lift to a combustion valve of an internal combustion engine having a camshaft phaser actuated by an electric motor for varying the phase relationship between a camshaft and a crankshaft of said internal combustion engine, said method comprising:

applying a variable electric current to said electric motor to achieve a desired camshaft phaser operational mode;

commanding said multi-mode valve train device to a desired valve train device operational mode selected from a high lift mode for providing high lift to said combustion valve and a low lift mode for providing low lift to said combustion valve;

monitoring said variable electric current or a parameter of said camshaft phaser that is indicative of said variable electric current;

calculating a first characteristic of said variable electric current or said parameter;

determining a first actual valve train device operational mode of said multi-mode valve train device by comparing said calculated first characteristic against a predetermined value of said first characteristic measured when said multi-mode valve train device is known to be in said desired valve train device operational mode.

2. A method as in claim 1 wherein said first characteristic is the amplitude of said variable electric current.

3. A method as in claim 1 wherein said first characteristic is the phase location of the peak of said variable electric current.

4. A method as in claim 1 further comprising:

determining said multi-mode valve train device is in said desired valve train device operational mode if said first actual valve train device operational mode matches said desired valve train device operational mode; or

determining said multi-mode valve train device is not in said desired valve train device operational mode if said first actual valve train device operational mode does not match said desired valve train device operational mode.

5. A method as in claim 1 further comprising:

calculating a second characteristic of said variable electric current or said parameter;

determining a second actual valve train device operational mode of said multi-mode valve train device by comparing said calculated second characteristic against a predetermined value of said second characteristic measured when said multi-mode valve train device is known to be in said desired valve train device operational mode; and either

determining said multi-mode valve train device is in said desired valve train device operational mode if said first actual valve train device operational mode and said second actual valve train device operational mode both match said desired valve train device operational mode; or

determining said multi-mode valve train device is not in said desired valve train device operational mode if at least one of said first actual valve train device operational mode and said second actual valve train device operational modes do not match said desired valve train device operational mode.

6. A method as in claim 1 wherein said internal combustion engine is a multi-cylinder internal combustion engine and at least two cylinders include a multi-mode valve train device, said method further comprising identifying which cylinder of said internal combustion engine said first actual valve train device operational mode matches said desired valve train device operational mode and which cylinder of said internal combustion engine said first actual valve train device operational mode does not match said desired valve train device operational mode by using a means for determining camshaft position.

7. A method for diagnosing first and second multi-mode valve train devices for selectively providing high lift and low lift to first and second combustion valves respectively of a cylinder of an internal combustion engine having a camshaft phaser actuated by an electric motor for varying the phase relationship between a camshaft and a crankshaft of said internal combustion engine, said method comprising:

applying a variable electric current to said electric motor to achieve a desired camshaft phaser operational mode;

commanding said first multi-mode valve train device to a desired first valve train device operational mode selected from a first high lift mode for providing high lift to said first combustion valve and a first low lift mode for providing low lift to said first combustion valve;

commanding said second multi-mode valve train device to a desired second valve train device operational mode selected from a second high lift mode for providing high lift to said second combustion valve and a second low lift mode for providing low lift to said second combustion valve;

monitoring said variable electric current or a parameter of said camshaft phaser that is indicative of said variable electric current;

calculating a characteristic of said variable electric current or said parameter;

determining an actual valve train device operational mode of said first and second multi-mode valve train devices by comparing said calculated characteristic against a predetermined value of said characteristic measured when said first and second multi-mode valve train devices are known to be in said desired first valve train device operational mode and said desired second valve train device operational mode respectively.

8. A method as in claim 7 wherein said characteristic is the amplitude of said variable electric current.

9. A method as in claim 7 further comprising determining if one or both of said first and second multi-mode valve train devices is not in said desired first valve train device operational mode and said desired second valve train device operational mode.

10. A method as in claim 9 wherein the extent to which said calculated characteristic differs from said predetermined value of said characteristic is used to determine if one or both of said first and second multi-mode valve train devices is not in said desired first valve train device operational mode and said desired second valve train device operational mode.