Diagnostic system and method for processing continuous and intermittent faults

1. A diagnostic system for diagnosing a device of a vehicle, comprising:

a first electronic circuit configured to generate samples of a parameter of the device;

a second electronic circuit configured to indicate whether each of the samples passed or failed based on comparisons of the samples with one of a predetermined value and a predetermined range;

a third electronic circuit configured to track a first number of consecutive samples compared, to track a second number of the first number of samples that failed, to track a third number of the first number of samples that failed consecutively, and to track a fourth number of a last predetermined number of samples compared that failed,

wherein the second electronic circuit is further configured to:

select one of a normal control mode, a temporary default action mode and a permanent default action mode based on the first, second, third, and fourth numbers;

transition from the normal control mode to the temporary default action mode and takes a temporary default action based on at least one of the third and fourth numbers;

transition to the permanent default action mode and takes a permanent default action based on at least one of the first, third, and fourth numbers; and

selectively set a diagnostic trouble code (DTC) in memory when in the permanent default action mode.

2. The diagnostic system of claim 1 further comprising a malfunction indicator lamp (MIL) that illuminates when the DTC is set.

3. The diagnostic system of claim 1 wherein the permanent default action is different than the temporary default action.

4. The diagnostic system of claim 1 wherein:

the third electronic circuit is further configured to track a period of operation in the temporary default action mode; and

the second electronic circuit is configured to transition to the permanent default action mode and to take the permanent default action in response to a determination that the period is greater than a predetermined period.

5. The diagnostic system of claim 1 wherein:

the third electronic circuit is further configured to track a fifth number of transitions from the normal control mode to the temporary default action mode; and

the second electronic circuit is configured to transition to the permanent default action mode and to take the permanent default action in response to a determination that the fifth number is greater than a predetermined value.

6. The diagnostic system of claim 1 wherein the second electronic circuit is configured to transition to the permanent default action mode and to take the permanent default action in response to a determination that the second number is greater than a predetermined value.

7. The diagnostic system of claim 1 wherein:

the third electronic circuit is further configured to track a period of operation in the temporary default action mode and to track a fifth number of transitions from the normal control mode to the temporary default action mode; and

the second electronic circuit is configured to transition to the permanent default action mode and to take the permanent default action in response to:

a first determination that the period is greater than a predetermined period;

a second determination that the fifth number is greater than a first predetermined value; and

a third determination that that the second number is greater than a second predetermined value.

8. The diagnostic system of claim 1 wherein the second electronic circuit is configured to transition to the temporary default action mode and to take the temporary default action in response to a determination that the third number is greater than a predetermined value.

9. The diagnostic system of claim 8 wherein the second electronic circuit is configured to transition to the temporary default action mode and to take the temporary default action further in response to a second determination that the fourth number is greater than a second predetermined value.

10. The diagnostic system of claim 8 wherein:

the third electronic circuit is further configured to track a fifth number of samples compared since a last failed sample; and

the second electronic circuit is configured to transition from the temporary default action mode to the normal control mode in response to a third determination that both:

the fifth number is greater than a third predetermined value; and

the fourth number is less than a fourth predetermined value.

11. A method, performed by an electronic circuit, for diagnosing a device of a vehicle, comprising:

generating samples of a parameter of the device;

indicating whether each of the samples passed or failed based on comparisons of the samples with one of a predetermined value and a predetermined range;

tracking a first number of consecutive samples compared, a second number of the first number of samples that failed, a third number of the first number of samples that failed consecutively, and a fourth number of a last predetermined number of samples compared that failed;

selecting one of a normal control mode, a temporary default action mode and a permanent default action mode based on the first, second, third, and fourth numbers;

transitioning from the normal control mode to the temporary default action mode and taking a temporary default action based on at least one of the third and fourth numbers;

transitioning to the permanent default action mode and taking a permanent default action based on at least one of the first, third, and fourth numbers; and

selectively setting a diagnostic trouble code (DTC) in memory when in the permanent default action mode.

12. The method of claim 11 further comprising illuminating a malfunction indicator lamp (MIL) when the DTC is set.

13. The method of claim 11 wherein the permanent default action is different than the temporary default action.

14. The method of claim 11 further comprising:

tracking a period of operation in the temporary default action mode; and

transitioning to the permanent default action mode and taking the permanent default action in response to a determination that the period is greater than a predetermined period.

15. The method of claim 11 further comprising:

tracking a fifth number of transitions from the normal control mode to the temporary default action mode; and

transitioning to the permanent default action mode and taking the permanent default action in response to a determination that the fifth number is greater than a predetermined value.

16. The method of claim 11 further comprising transitioning to the permanent default action mode and taking the permanent default action in response to a determination that the second number is greater than a predetermined value.

17. The method of claim 11 further comprising:

tracking a period of operation in the temporary default action mode;

tracking a fifth number of transitions from the normal control mode to the temporary default action mode; and

transitioning to the permanent default action mode and taking the permanent default action in response to:

a first determination that the period is greater than a predetermined period;

a second determination that the fifth number is greater than a first predetermined value; and

a third determination that that the second number is greater than a second predetermined value.

18. The method of claim 11 further comprising transitioning to the temporary default action mode and taking the temporary default action in response to a determination that the third number is greater than a predetermined value.

19. The method of claim 18 further comprising transitioning to the temporary default action mode and taking the temporary default action further in response to a second determination that the fourth number is greater than a second predetermined value.

20. The method of claim 18 further comprising:

tracking a fifth number of samples compared since a last failed sample; and

transitioning from the temporary default action mode to the normal control mode in response to a third determination that both:

the fifth number is greater than a third predetermined value; and

the fourth number is less than a fourth predetermined value.

21. The diagnostic system of claim 1 wherein the first, second, and third electronic circuits include or are a part of at least one of: an application specific integrated circuit (ASIC); a discrete circuit; an integrated circuit; a combinational logic circuit; a field programmable gate array; and a processor and memory including code.