System for detecting operating errors in a variable valve timing engine using pressure sensors

1. A method comprising:

measuring, using a pressure signal module, cylinder pressures at a plurality of points of a combustion cycle;

retrieving, using a pressure sensor data comparison module, predetermined cylinder pressures for the plurality of points from memory;

comparing, using the pressure sensor data comparison module, the predetermined cylinder pressures to the measured cylinder pressures;

determining, using the pressure sensor data comparison module, variances based on the measured cylinder pressures and the predetermined cylinder pressures;

selectively, using a valve actuation hardware remedy module, diagnosing a fault in a switchable roller finger follower (SRFF) mechanism based on the variances; and

performing, using the valve actuation hardware remedy module, a valve actuation hardware remedy in response to the fault in the SRFF mechanism.

2. A method as recited in claim 1 wherein measuring the cylinder pressures comprises measuring the cylinder pressures based on an in-cylinder pressure signal from a cylinder pressure sensor.

3. A method as recited in claim 1 further comprising determining measured pressure volume segments based on the measured cylinder pressures.

4. A method as recited in claim 3 further comprising:

determining an engine position; and

determining the measured pressure volume segments further based on the engine position.

5. A method as recited in claim 4 further comprising:

determining an engine temperature; and

determining the measured pressure volume segments further based on the engine temperature.

6. A method as recited in claim 5 wherein determining the engine position comprises determining a crankshaft angle window.

7. A method as recited in claim 1 further comprising filtering the measured cylinder pressures before the comparison.

8. A method as recited in claim 1 wherein the valve actuation hardware remedy comprises reducing an engine speed.

9. A method as recited in claim 1 further comprising indicating that the SRFF mechanism is stuck in a high lift state.

10. A method as recited in claim 1 further comprising indicating that the SRFF mechanism is stuck in a low lift state.

11. A control module comprising:

a pressure signal module that generates measured cylinder pressures at a plurality of points of a combustion cycle;

a pressure sensor data comparison module that retrieves predetermined cylinder pressures for the plurality of points from memory, that compares the measured cylinder pressures to the predetermined pressures, and that determines variances based on the measured cylinder pressures and the predetermined cylinder pressures; and

a valve actuation hardware remedy module that selectively diagnoses a fault in a switchable roller finger follower (SRFF) mechanism based on the variances and that performs a hardware actuation remedy in response to the fault in the SRFF mechanism.

12. A control module as recited in claim 11 further comprising a pressure processing module that filters the measured cylinder pressures before the comparison.

13. A control module as recited in claim 11 further comprising an engine position module that determines an engine position,

wherein the pressure sensor data comparison module determines measured pressure volume segments based on the engine position and the measured cylinder pressures.

14. A control module as recited in claim 13 wherein the pressure sensor data comparison module determines the measured pressure volume segments further based on an engine temperature.

15. A control module as recited in claim 12 wherein, based on the variances, the valve actuation hardware remedy module selectively indicates that the SRFF mechanism is stuck in one of a high lift state and a low lift state.

16. A control module as recited in claim 11 wherein, in response to the fault in the SRFF mechanism, the valve actuation hardware remedy module reduces engine speed.