Claims
- 1. A diagnostic method for a reciprocating internal combustion engine system having a shaft sensor responsive to an engine shaft for producing a shaft signal indicative of movement of said engine shaft, the method comprising the steps of:
producing an air intake signal responsive to air intake of said engine; analyzing said air intake signal to detect a dynamic variation in the air intake that is characteristic of engine rotation; and diagnosing a failure of said shaft sensor when said dynamic variation is detected but said shaft signal indicates that said shaft is not moving.
- 2. The diagnostic method of claim 1, wherein said air intake signal is produced by sensing mass airflow in a throttle passage of said engine.
- 3. The diagnostic method of claim 1, wherein said air intake signal is produced by sensing a pressure in an intake manifold of said engine.
- 4. The diagnostic method of claim 3, where the step of analyzing said air intake signal includes the steps of:
measuring an ambient air pressure; computing a relative air pressure signal based on a difference between said air intake signal and the measured ambient air pressure; comparing said relative air pressure signal to upper and lower thresholds to identify successive excursions of said relative air pressure signal above said upper threshold and below said lower threshold; and detecting a dynamic variation in said air intake when a predetermined number of said successive excursions have been identified.
- 5. The diagnostic method of claim 1, where the step of analyzing said air intake signal includes the steps of:
detecting increases and decreases of said air intake signal over given intervals of time; identifying successive detected increases of said air intake signal in excess of a first threshold and detected decreases of said air intake signal in excess of a second threshold; and detecting a dynamic variation in said air intake when a predetermined number of said successive detected increases and decreases have been identified.
- 6. The diagnostic method of claim 1, where the step of analyzing said air intake signal includes the steps of:
determining a derivative of said air intake signal; using the determined derivative to identify successive positive and negative inflections of said air intake signal; and detecting a dynamic variation in said air intake when a predetermined number of said successive positive and negative inflections have been identified.
- 7. The diagnostic method of claim 6, including the steps of:
computing changes in said air intake signal over a number of successive time intervals; determining the derivative of said air intake signal based on a change in successively computed changes; detecting a positive inflection of said air intake signal when said derivative is substantially zero and the computed change in the air intake signal is positive; detecting a negative inflection of said air intake signal when said derivative is substantially zero and the computed change in the air intake signal is negative.
Parent Case Info
[0001] This application claims priority to U.S. Provisional Application No. 60/208,236 filed May 31, 2000.
Provisional Applications (1)
|
Number |
Date |
Country |
|
60208236 |
May 2000 |
US |