Powertrain and ignition diagnostic system and method

1. A control system, comprising:

a powertrain relay diagnostic module that determines a single continuous period that a powertrain relay voltage is less than an ignition relay voltage, that compares said single continuous period to a single predetermined period, and that diagnoses a powertrain relay out of correlation (OOC) error when said single continuous period is greater than or equal to said single predetermined period; and

an ignition relay diagnostic module that diagnoses an ignition relay OOC error when said ignition relay voltage is less than said powertrain relay voltage for a first predetermined cumulative period within a first predetermined total period.

2. The control system of claim 1 wherein said powertrain relay diagnostic module diagnoses said powertrain relay OOC error when a difference between said ignition relay voltage and said powertrain relay voltage is greater than a continuous powertrain relay correlation threshold.

3. The control system of claim 1 wherein said ignition relay diagnostic module diagnoses said ignition relay OOC error when a difference between said powertrain relay voltage and said ignition relay voltage is greater than an ignition relay correlation threshold.

4. The control system of claim 1 further comprising an electronic throttle control (ETC) diagnostic module that selectively diagnoses an ETC actuation error when a difference between desired and actual throttle positions is not within a predetermined ETC actuation error range.

5. The control system of claim 4 wherein said ETC diagnostic module selectively diagnoses said ETC actuation error when said difference between said desired and actual throttle positions is not within said predetermined ETC actuation error range for a predetermined ETC actuation error period.

6. The control system of claim 5 wherein said predetermined ETC actuation error period is greater than said single predetermined period.

7. The control system of claim 6 wherein said ETC diagnostic module suspends diagnosing said ETC actuation error when said powertrain relay diagnostic module diagnoses said powertrain relay OOC error.

8. The control system of claim 1 wherein said powertrain relay diagnostic module diagnoses said powertrain relay OOC error when said powertrain relay voltage is less than said ignition relay voltage for a second predetermined cumulative period within a second predetermined total period.

9. The control system of claim 8 wherein said powertrain relay diagnostic module diagnoses said powertrain relay OOC error when a difference between said ignition relay voltage and said powertrain relay voltage is greater than an intermittent powertrain relay correlation threshold.

10. The control system of claim 1 wherein said powertrain relay voltage is supplied to a powertrain component and said ignition relay voltage is supplied to at least one of an ignition component and a non-ignition component.

11. A method, comprising:

determining a single continuous period that a powertrain relay voltage is less than an ignition relay voltage;

comparing said single continuous period to a single predetermined period;

diagnosing a powertrain relay out of correlation (OOC) error when said single continuous period is greater than or equal to said single predetermined period; and

diagnosing an ignition relay OOC error when said ignition relay voltage is less than said powertrain relay voltage for a first predetermined cumulative period within a first predetermined total period.

12. The method of claim 11 further comprising diagnosing said powertrain relay OOC error when a difference between said ignition relay voltage and said powertrain relay voltage is greater than a continuous powertrain relay correlation threshold.

13. The method of claim 11 further comprising diagnosing said ignition relay OOC error when a difference between said powertrain relay voltage and said ignition relay voltage is greater than an ignition relay correlation threshold.

14. The method of claim 11 further comprising selectively diagnosing an ETC actuation error when a difference between desired and actual throttle positions is not within a predetermined ETC actuation error range.

15. The method of claim 14 further comprising selectively diagnosing said ETC actuation error when said difference between said desired and actual throttle positions is not within said predetermined ETC actuation error range for a predetermined ETC actuation error period.

16. The method of claim 15 wherein said predetermined ETC actuation error period is greater than said single predetermined period.

17. The method of claim 16 further comprising suspending diagnosing said ETC actuation error when said powertrain relay OOC error is diagnosed.

18. The method of claim 11 further comprising diagnosing said powertrain relay OOC error when said powertrain relay voltage is less than said ignition relay voltage for a second predetermined cumulative period within a second predetermined total period.

19. The method of claim 18 further comprising diagnosing said powertrain relay OOC error when a difference between said ignition relay voltage and said powertrain relay voltage is greater than an intermittent powertrain relay correlation threshold.

20. The method of claim 11 wherein said powertrain relay voltage is supplied to a powertrain component and said ignition relay voltage is supplied to at least one of an ignition component and a non-ignition component.