Method for diagnosing sticking of lubrication control valve of hybrid vehicle

1. A method of diagnosing sticking of a lubrication control valve of a hybrid vehicle, the method comprising:

by a transmission control unit (TCU), determining driving intention of a driver;

when determined that there is the driver's driving intention, requesting a hybrid control unit (HCU) to diagnose sticking of an independent type lubrication control valve;

determining, by the HCU, whether or not to permit a sticking diagnosis request of the TCU;

ordering, by the HCU, pressure to the TCU for operating clutch engagement to an engine clutch, after permitting the sticking diagnosis;

by the TCU, turning on an electric oil pump which supplies fluid pressure for the engine clutch engagement and controlling an operating speed of the electric oil pump in accordance with pressure order for the engine clutch engagement of the HCU;

measuring, by an engine clutch pressure sensor, engine clutch engagement pressure in a state in which the engine clutch is engaged by the fluid pressure supplied from the electric oil pump, by measuring first engine clutch engagement pressure in an off-state of the independent type lubrication control valve and second engine clutch engagement pressure in an on-state thereof; and

determining, by the TCU, whether or not the independent type lubrication control valve is stuck, on the basis of a pressure difference between the first engine clutch engagement pressure and the second engine clutch engagement pressure.

2. The method of claim 1 , wherein, when the TCU receives a brake pedal stroke-off signal, a P-stage signal, a signal with a current vehicle speed of zero, an engine speed of zero, and a motor speed of zero, the TCU determines that the driver has no intention of driving and requests the HCU for the sticking diagnosis of the independent type lubrication control valve.

3. The method of claim 1 , wherein, when the TCU is in a normal state possible to diagnose sticking and there is no sticking diagnosis during one driving cycle of the vehicle, the TCU requests the HCU for the sticking diagnosis of the independent type lubrication control valve.

4. The method of claim 1 , wherein the HCU permits the sticking diagnosis of the independent type lubrication control valve in a non-learning engine clutch state and a normal state of the engine clutch pressure sensor, after confirming whether the engine clutch performs learning operation and the engine clutch pressure sensor is in the normal state or not.

5. The method of claim 1 , wherein, in the determining whether or not the independent type lubrication control valve is stuck, when the pressure difference is equal to or higher than a reference value, the TCU determines that on/off operation of the independent type lubrication control valve is normally performed and then outputs to a dashboard that the independent type lubrication control valve is in a normal state.

6. The method of claim 1 , wherein, in the determining whether or not the independent type lubrication control valve is stuck, when the pressure difference is less than the reference value, the TCU determines that the independent type lubrication control valve is stuck and then outputs to the dashboard that the independent type lubrication control valve is in a stuck and failed state.