Low pressure of oil can testify from need of repair of the engine. The control lamp of pressure of oil serves for the alarm system that oil pressure dangerously low. Even the manometer on a combination of devices shows only relative pressure. Pressure of oil needs to be checked the certified mechanical (not electric) manometer.
The sensor of pressure of oil is installed in an end face of a head of the block of cylinders from opposite to the drive of the gas-distributing mechanism. Turn out the sensor and instead of it screw a manometer hose tip.
Connect to the engine a tachometer according to the maintenance instruction attached to it.
Launch the engine and warm up it up to the working temperature. Check oil pressure at a frequency of rotation of idling and at 3000 min.-1. If pressure is lower demanded, perhaps, the gap in bearings of a bent shaft is increased or the oil pump is faulty.