Method for sensing reverse rotation of engine in vehicle using tooth period ratio of crankshaft

A method for sensing a reverse rotation of an engine in a vehicle, wherein a pulse signal is received from a crankshaft angle detection sensor provided to detect a crankshaft angle of the engine and a reverse rotation state of the engine in the vehicle is determined based on a tooth period ratio between a falling edge and the next falling edge of the pulse signal, the method comprising:

• detecting, by an electronic control unit (ECU), tooth period ratios using the crankshaft angle detection sensor and storing the detected tooth period ratios in a buffer of the ECU;
• calculating, by the ECU, a first tooth period ratio which is a ratio between a first measured tooth period and a previous tooth period measured just before the first measured tooth period;
• determining, by the ECU, whether a value of the first tooth period ratio is greater than a first reference value;
• updating, by the ECU, a tooth period value, which is stored in the buffer previously by measuring a second tooth period, when the first tooth period ratio is greater than the first reference value;
• calculating, by the ECU, a second tooth period ratio using a value of e second tooth period;
• and
• determining, by the ECU, the reverse rotation state of the engine by checking whether a change between the first tooth period ratio and the second tooth period ratio shows a predetermined pattern.