oil pressure error light on, but not sensor problem?

[timkee330ci]

It's a 2001 3200gt, automatic. The oil pressure light came on when the engine is below about 1200 rpm.
The oil pressure sensor was changed by dealer in Feb 2013. Since it was only half a year since the last change, i took it back to the dealer asked them to look at the problem.
After two weeks long the mechanic told me it's not the sensor problem because the light is still on after testing with a brand new sensor.
I would like to ask if it's not the sensor, what other problem may cause the error light? I am sure the oil is topped up to the max level.
Could it be the wiring? Or the oil pump not working, delivering inadqueate pressure? How could the dealer diagnose the problem?

Now the car has been with the dealer for three weeks and i really miss it! Guys please give me some ideas, thanks!

 

[allandwf]

Have them try and connect in a gauge perhaps? Prove what the pressure really is.

 

[BennyD]

Have a look at the engine earth strap. I had a fluctuating/zero oil pressure problem and a new lead cured it. First of all, ask your dealer to confirm there is oil pressure by using a mechanical gauge so you know for sure it is an indication fault. Then try another instrument binnacle if he has one, even one off another car would do. Good luck!

 

[conaero]

The oil sensor wire runs across the top of the engine and thus goes crispy over time.

Its worth hot wiring the sensor to make sure you have an accurate reading or as the other guys say get a separate gauge fitted to get a proper reading.

Other than that check the relief spring or you may want to consider endfloat test or a failing oil pump!

Being an auto endfloat is uncommon but worth checking before your engine lunches itself.

If your engine is a high miler (100k plus) it may just be time for a rebuild as the internal tolerances will have increased thus the pressure drops off, bit like putting your finger over the end of a hose pipe type scenario.