big help please, oil light Options

[trackdaydavid]

I have a 3sge engined celica and when i start the car up no oil light soon as i start to drive carefully the orange oil level light comes on and stays on untill i switch the engine off. I have changed the oil and the filter and used an engine flush, no difference! engine does not make any rattling noise and i have taken rocker cover off and seems plenty of oil and not grooves or noticable damage to any parts. Checked oil level on dipstick reads full. Stuck do i need to worry or is there an engine oil level sensor that is in the sump on these models. Any help would be really appreciated don't know what to do garage suggested oil pump but no red oil light has come on and engine not noisy and looks well lubricated. Thanks.