Any time you even begin to suspect a possible oiling issue pre-mix your fuel at least to a 50:1 mixture. This way if there is any oiling problem you won't burn down your motor so fast. If the oiling system turns out to be fine the motor will just smoke a bit more through that tank of fuel.
If your system has an on-board oil tank it is plumbed to keep the motor tank full by pulses of crankcase pressure. You need the factory service manual for the procedure to test the correct hose fitting/valve for correct function. You can also loosen the cap on the motor tank and if the system is working correctly, the tank should refil. If not, follow testing laid out in the manual.
Some systems the motor oil pump has a rotation sensor in the pump. Pulses from this sensor are compared to ignition pulses from one of the ignition coils. If either the rotation sensor or the ign coil fail to pulse an alarm goes off. Check spark on all cyls to be sure this alarm is not caused by a failing ign. Test rotation sensor following tests laid out in the service manual.