Patent ID: 7110868

Claim:
A method for determining a state of an engine speed sensor for a vehicle, the method comprising: determining the engine speed sensor as being in a normal state when a signal is generated in the engine speed sensor and checking a start switch when a signal is not generated in the engine speed sensor; determining the engine speed sensor as being in the normal state when the start switch is off and judging whether a signal of a camshaft position sensor indicates more than two revolutions when the start switch is in the start state; determining the engine speed sensor as being in a normal state when the signal of the camshaft position sensor indicates more than two revolutions and determining the engine speed sensor as being in a state of failure when the signal of the camshaft position sensor indicates less than two revolutions; determining the engine speed sensor as being be in a normal state when the start switch is on and the signal of the camshaft position sensor indicates less than one revolution, and determining the engine speed sensor as being in a state of temporary failure and switching into a failure mode when the start switch is on and the signal of the camshaft position sensor indicates more than two revolutions; and determining the engine speed sensor as being in a normal state when the signal from the camshaft position sensor is stopped and determining the engine speed sensor as being in a state of permanent failure when the signal is continuously generated in the camshaft position sensor.